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### 16.9 Standard Pattern Names For Generation

Here is a table of the instruction names that are meaningful in the RTL generation pass of the compiler. Giving one of these names to an instruction pattern tells the RTL generation pass that it can use the pattern to accomplish a certain task.

‘`movm`’
  Here m stands for a two-letter machine mode name, in lowercase. This instruction pattern moves data with that machine mode from operand 1 to operand 0. For example, ‘`movsi`’ moves full-word data.

  If operand 0 is a `subreg` with mode m of a register whose own mode is wider than m, the effect of this instruction is to store the specified value in the part of the register that corresponds to mode m. Bits outside of m, but which are within the same target word as the `subreg` are undefined. Bits which are outside the target word are left unchanged.

  This class of patterns is special in several ways. First of all, each of these names up to and including full word size must be defined, because there is no other way to copy a datum from one place to another. If there are patterns accepting operands in larger modes, ‘`movm`’ must be defined for integer modes of those sizes.

  Second, these patterns are not used solely in the RTL generation pass. Even the reload pass can generate move insns to copy values from stack slots into temporary registers. When it does so, one of the operands is a hard register and the other is an operand that can need to be reloaded into a register.

  Therefore, when given such a pair of operands, the pattern must generate RTL which needs no reloading and needs no temporary registers—no registers other than the operands. For example, if you support the pattern with a `define_expand`, then in such a case the `define_expand` mustn't call `force_reg` or any other such function which might generate new pseudo registers.

  This requirement exists even for subword modes on a RISC machine where fetching those modes from memory normally requires several insns and some temporary registers.

  During reload a memory reference with an invalid address may be passed as an operand. Such an address will be replaced with a valid address later in the reload pass. In this case, nothing may be done with the address except to use it as it stands. If it is copied, it will not be replaced with a valid address. No attempt should be made to make such an address into a valid address and no routine (such as `change_address`) that will do so may be called. Note that `general_operand` will fail when applied to such an address.

  The global variable `reload_in_progress` (which must be explicitly declared if required) can be used to determine whether such special handling is required.

  The variety of operands that have reloads depends on the rest of the machine description, but typically on a RISC machine these can only be pseudo registers that did not get hard registers, while on other machines explicit memory references will get optional reloads.

  If a scratch register is required to move an object to or from memory, it can be allocated using `gen_reg_rtx` prior to life analysis.

  If there are cases which need scratch registers during or after reload, you must provide an appropriate secondary_reload target hook.

  The macro `can_create_pseudo_p` can be used to determine if it is unsafe to create new pseudo registers. If this variable is nonzero, then it is unsafe to call `gen_reg_rtx` to allocate a new pseudo.

  The constraints on a ‘`movm`’ must permit moving any hard register to any other hard register provided that `HARD_REGNO_MODE_OK` permits mode m in both registers and `TARGET_REGISTER_MOVE_COST` applied to their classes returns a value of 2.

  It is obligatory to support floating point ‘`movm`’ instructions into and out of any registers that can hold fixed point values, because unions and structures (which have modes `SImode` or `DImode`) can be in those registers and they may have floating point members.

  There may also be a need to support fixed point ‘`movm`’ instructions in and out of floating point registers. Unfortunately, I have forgotten why this was so, and I don't know whether it is still true. If `HARD_REGNO_MODE_OK` rejects fixed point values in floating point registers, then the constraints of the fixed point ‘`movm`’ instructions must be designed to avoid ever trying to reload into a floating point register.

‘`reload_inm`’
‘`reload_outm`’
  These named patterns have been obsoleted by the target hook `secondary_reload`.

  Like ‘`movm`’, but used when a scratch register is required to move between operand 0 and operand 1. Operand 2 describes the scratch register. See the discussion of the `SECONDARY_RELOAD_CLASS` macro in see Register Classes.

  There are special restrictions on the form of the `match_operand`s used in these patterns. First, only the predicate for the reload operand is examined, i.e., `reload_in` examines operand 1, but not the predicates for operand 0 or 2. Second, there may be only one alternative in the constraints. Third, only a single register class letter may be used for the constraint; subsequent constraint letters are ignored. As a special exception, an empty constraint string matches the `ALL_REGS` register class. This may relieve ports of the burden of defining an `ALL_REGS` constraint letter just for these patterns.

‘`movstrictm`’
  Like ‘`movm`’ except that if operand 0 is a `subreg` with mode m of a register whose natural mode is wider, the ‘`movstrictm`’ instruction is guaranteed not to alter any of the register except the part which belongs to mode m.

‘`movmisalignm`’
  This variant of a move pattern is designed to load or store a value from a memory address that is not naturally aligned for its mode. For a store, the memory will be in operand 0; for a load, the memory will be in operand 1. The other operand is guaranteed not to be a memory, so that it's easy to tell whether this is a load or store.

  This pattern is used by the autovectorizer, and when expanding a `MISALIGNED_INDIRECT_REF` expression.

‘`load_multiple`’
  Load several consecutive memory locations into consecutive registers. Operand 0 is the first of the consecutive registers, operand 1 is the first memory location, and operand 2 is a constant: the number of consecutive registers.

  Define this only if the target machine really has such an instruction; do not define this if the most efficient way of loading consecutive registers from memory is to do them one at a time.

  On some machines, there are restrictions as to which consecutive registers can be stored into memory, such as particular starting or ending register numbers or only a range of valid counts. For those machines, use a `define_expand` (see Expander Definitions) and make the pattern fail if the restrictions are not met.

  Write the generated insn as a `parallel` with elements being a `set` of one register from the appropriate memory location (you may also need `use` or `clobber` elements). Use a `match_parallel` (see RTL Template) to recognize the insn. See `rs6000.md` for examples of the use of this insn pattern.

‘`store_multiple`’
  Similar to ‘`load_multiple`’, but store several consecutive registers into consecutive memory locations. Operand 0 is the first of the consecutive memory locations, operand 1 is the first register, and operand 2 is a constant: the number of consecutive registers.

‘`vec_load_lanesmn`’
  Perform an interleaved load of several vectors from memory operand 1 into register operand 0. Both operands have mode m. The register operand is viewed as holding consecutive vectors of mode n, while the memory operand is a flat array that contains the same number of elements. The operation is equivalent to:

                int c = GET_MODE_SIZE (m) / GET_MODE_SIZE (n);
                for (j = 0; j < GET_MODE_NUNITS (n); j++)
                  for (i = 0; i < c; i++)
                    operand0[i][j] = operand1[j * c + i];

  For example, ‘`vec_load_lanestiv4hi`’ loads 8 16-bit values from memory into a register of mode ‘`TI`’. The register contains two consecutive vectors of mode ‘`V4HI`’.

  This pattern can only be used if:

                TARGET_ARRAY_MODE_SUPPORTED_P (n, c)

  is true. GCC assumes that, if a target supports this kind of instruction for some mode n, it also supports unaligned loads for vectors of mode n.

‘`vec_store_lanesmn`’
  Equivalent to ‘`vec_load_lanesmn`’, with the memory and register operands reversed. That is, the instruction is equivalent to:

                int c = GET_MODE_SIZE (m) / GET_MODE_SIZE (n);
                for (j = 0; j < GET_MODE_NUNITS (n); j++)
                  for (i = 0; i < c; i++)
                    operand0[j * c + i] = operand1[i][j];

  for a memory operand 0 and register operand 1.

‘`vec_setm`’
  Set given field in the vector value. Operand 0 is the vector to modify, operand 1 is new value of field and operand 2 specify the field index.

‘`vec_extractm`’
  Extract given field from the vector value. Operand 1 is the vector, operand 2 specify field index and operand 0 place to store value into.

‘`vec_initm`’
  Initialize the vector to given values. Operand 0 is the vector to initialize and operand 1 is parallel containing values for individual fields.

‘`vcondmn`’
  Output a conditional vector move. Operand 0 is the destination to receive a combination of operand 1 and operand 2, which are of mode m, dependent on the outcome of the predicate in operand 3 which is a vector comparison with operands of mode n in operands 4 and 5. The modes m and n should have the same size. Operand 0 will be set to the value op1 & msk | op2 & ~msk where msk is computed by element-wise evaluation of the vector comparison with a truth value of all-ones and a false value of all-zeros.

‘`vec_permm`’
  Output a (variable) vector permutation. Operand 0 is the destination to receive elements from operand 1 and operand 2, which are of mode m. Operand 3 is the selector. It is an integral mode vector of the same width and number of elements as mode m.

  The input elements are numbered from 0 in operand 1 through 2*N-1 in operand 2. The elements of the selector must be computed modulo 2*N. Note that if `rtx_equal_p(operand1, operand2)`, this can be implemented with just operand 1 and selector elements modulo N.

  In order to make things easy for a number of targets, if there is no ‘`vec_perm`’ pattern for mode m, but there is for mode q where q is a vector of `QImode` of the same width as m, the middle-end will lower the mode m `VEC_PERM_EXPR` to mode q.

‘`vec_perm_constm`’
  Like ‘`vec_perm`’ except that the permutation is a compile-time constant. That is, operand 3, the selector, is a `CONST_VECTOR`.

  Some targets cannot perform a permutation with a variable selector, but can efficiently perform a constant permutation. Further, the target hook `vec_perm_ok` is queried to determine if the specific constant permutation is available efficiently; the named pattern is never expanded without `vec_perm_ok` returning true.

  There is no need for a target to supply both ‘`vec_permm`’ and ‘`vec_perm_constm`’ if the former can trivially implement the operation with, say, the vector constant loaded into a register.

‘`pushm1`’
  Output a push instruction. Operand 0 is value to push. Used only when `PUSH_ROUNDING` is defined. For historical reason, this pattern may be missing and in such case an `mov` expander is used instead, with a `MEM` expression forming the push operation. The `mov` expander method is deprecated.

‘`addm3`’
  Add operand 2 and operand 1, storing the result in operand 0. All operands must have mode m. This can be used even on two-address machines, by means of constraints requiring operands 1 and 0 to be the same location.

‘`addptrm3`’
  Like `add` m `3` but is guaranteed to only be used for address calculations. The expanded code is not allowed to clobber the condition code. It only needs to be defined if `add` m `3` sets the condition code. If adds used for address calculations and normal adds are not compatible it is required to expand a distinct pattern (e.g. using an unspec). The pattern is used by LRA to emit address calculations. `add` m `3` is used if `addptr` m `3` is not defined.

‘`ssaddm3`’, ‘`usaddm3`’
‘`subm3`’, ‘`sssubm3`’, ‘`ussubm3`’
‘`mulm3`’, ‘`ssmulm3`’, ‘`usmulm3`’
‘`divm3`’, ‘`ssdivm3`’
‘`udivm3`’, ‘`usdivm3`’
‘`modm3`’, ‘`umodm3`’
‘`uminm3`’, ‘`umaxm3`’
‘`andm3`’, ‘`iorm3`’, ‘`xorm3`’
  Similar, for other arithmetic operations.

‘`fmam4`’
  Multiply operand 2 and operand 1, then add operand 3, storing the result in operand 0 without doing an intermediate rounding step. All operands must have mode m. This pattern is used to implement the `fma`, `fmaf`, and `fmal` builtin functions from the ISO C99 standard.

‘`fmsm4`’
  Like `fma` m `4`, except operand 3 subtracted from the product instead of added to the product. This is represented in the rtl as

                (fma:m op1 op2 (neg:m op3))

‘`fnmam4`’
  Like `fma` m `4` except that the intermediate product is negated before being added to operand 3. This is represented in the rtl as

                (fma:m (neg:m op1) op2 op3)

‘`fnmsm4`’
  Like `fms` m `4` except that the intermediate product is negated before subtracting operand 3. This is represented in the rtl as

                (fma:m (neg:m op1) op2 (neg:m op3))

‘`sminm3`’, ‘`smaxm3`’
  Signed minimum and maximum operations. When used with floating point, if both operands are zeros, or if either operand is `NaN`, then it is unspecified which of the two operands is returned as the result.

‘`reduc_smin_m`’, ‘`reduc_smax_m`’
  Find the signed minimum/maximum of the elements of a vector. The vector is operand 1, and the scalar result is stored in the least significant bits of operand 0 (also a vector). The output and input vector should have the same modes.

‘`reduc_umin_m`’, ‘`reduc_umax_m`’
  Find the unsigned minimum/maximum of the elements of a vector. The vector is operand 1, and the scalar result is stored in the least significant bits of operand 0 (also a vector). The output and input vector should have the same modes.

‘`reduc_splus_m`’
  Compute the sum of the signed elements of a vector. The vector is operand 1, and the scalar result is stored in the least significant bits of operand 0 (also a vector). The output and input vector should have the same modes.

‘`reduc_uplus_m`’
  Compute the sum of the unsigned elements of a vector. The vector is operand 1, and the scalar result is stored in the least significant bits of operand 0 (also a vector). The output and input vector should have the same modes.

‘`sdot_prodm`’
‘`udot_prodm`’
  Compute the sum of the products of two signed/unsigned elements. Operand 1 and operand 2 are of the same mode. Their product, which is of a wider mode, is computed and added to operand 3. Operand 3 is of a mode equal or wider than the mode of the product. The result is placed in operand 0, which is of the same mode as operand 3.

‘`ssum_widenm3`’
‘`usum_widenm3`’
  Operands 0 and 2 are of the same mode, which is wider than the mode of operand 1. Add operand 1 to operand 2 and place the widened result in operand 0. (This is used express accumulation of elements into an accumulator of a wider mode.)

‘`vec_shl_m`’, ‘`vec_shr_m`’
  Whole vector left/right shift in bits. Operand 1 is a vector to be shifted. Operand 2 is an integer shift amount in bits. Operand 0 is where the resulting shifted vector is stored. The output and input vectors should have the same modes.

‘`vec_pack_trunc_m`’
  Narrow (demote) and merge the elements of two vectors. Operands 1 and 2 are vectors of the same mode having N integral or floating point elements of size S. Operand 0 is the resulting vector in which 2*N elements of size N/2 are concatenated after narrowing them down using truncation.

‘`vec_pack_ssat_m`’, ‘`vec_pack_usat_m`’
  Narrow (demote) and merge the elements of two vectors. Operands 1 and 2 are vectors of the same mode having N integral elements of size S. Operand 0 is the resulting vector in which the elements of the two input vectors are concatenated after narrowing them down using signed/unsigned saturating arithmetic.

‘`vec_pack_sfix_trunc_m`’, ‘`vec_pack_ufix_trunc_m`’
  Narrow, convert to signed/unsigned integral type and merge the elements of two vectors. Operands 1 and 2 are vectors of the same mode having N floating point elements of size S. Operand 0 is the resulting vector in which 2*N elements of size N/2 are concatenated.

‘`vec_unpacks_hi_m`’, ‘`vec_unpacks_lo_m`’
  Extract and widen (promote) the high/low part of a vector of signed integral or floating point elements. The input vector (operand 1) has N elements of size S. Widen (promote) the high/low elements of the vector using signed or floating point extension and place the resulting N/2 values of size 2*S in the output vector (operand 0).

‘`vec_unpacku_hi_m`’, ‘`vec_unpacku_lo_m`’
  Extract and widen (promote) the high/low part of a vector of unsigned integral elements. The input vector (operand 1) has N elements of size S. Widen (promote) the high/low elements of the vector using zero extension and place the resulting N/2 values of size 2*S in the output vector (operand 0).

‘`vec_unpacks_float_hi_m`’, ‘`vec_unpacks_float_lo_m`’
‘`vec_unpacku_float_hi_m`’, ‘`vec_unpacku_float_lo_m`’
  Extract, convert to floating point type and widen the high/low part of a vector of signed/unsigned integral elements. The input vector (operand 1) has N elements of size S. Convert the high/low elements of the vector using floating point conversion and place the resulting N/2 values of size 2*S in the output vector (operand 0).

‘`vec_widen_umult_hi_m`’, ‘`vec_widen_umult_lo_m`’
‘`vec_widen_smult_hi_m`’, ‘`vec_widen_smult_lo_m`’
‘`vec_widen_umult_even_m`’, ‘`vec_widen_umult_odd_m`’
‘`vec_widen_smult_even_m`’, ‘`vec_widen_smult_odd_m`’
  Signed/Unsigned widening multiplication. The two inputs (operands 1 and 2) are vectors with N signed/unsigned elements of size S. Multiply the high/low or even/odd elements of the two vectors, and put the N/2 products of size 2*S in the output vector (operand 0). A target shouldn't implement even/odd pattern pair if it is less efficient than lo/hi one.

‘`vec_widen_ushiftl_hi_m`’, ‘`vec_widen_ushiftl_lo_m`’
‘`vec_widen_sshiftl_hi_m`’, ‘`vec_widen_sshiftl_lo_m`’
  Signed/Unsigned widening shift left. The first input (operand 1) is a vector with N signed/unsigned elements of size S. Operand 2 is a constant. Shift the high/low elements of operand 1, and put the N/2 results of size 2*S in the output vector (operand 0).

‘`mulhisi3`’
  Multiply operands 1 and 2, which have mode `HImode`, and store a `SImode` product in operand 0.

‘`mulqihi3`’, ‘`mulsidi3`’
  Similar widening-multiplication instructions of other widths.

‘`umulqihi3`’, ‘`umulhisi3`’, ‘`umulsidi3`’
  Similar widening-multiplication instructions that do unsigned multiplication.

‘`usmulqihi3`’, ‘`usmulhisi3`’, ‘`usmulsidi3`’
  Similar widening-multiplication instructions that interpret the first operand as unsigned and the second operand as signed, then do a signed multiplication.

‘`smulm3_highpart`’
  Perform a signed multiplication of operands 1 and 2, which have mode m, and store the most significant half of the product in operand 0. The least significant half of the product is discarded.

‘`umulm3_highpart`’
  Similar, but the multiplication is unsigned.

‘`maddmn4`’
  Multiply operands 1 and 2, sign-extend them to mode n, add operand 3, and store the result in operand 0. Operands 1 and 2 have mode m and operands 0 and 3 have mode n. Both modes must be integer or fixed-point modes and n must be twice the size of m.

  In other words, `madd` m n `4` is like `mul` m n `3` except that it also adds operand 3.

  These instructions are not allowed to `FAIL`.

‘`umaddmn4`’
  Like `madd` m n `4`, but zero-extend the multiplication operands instead of sign-extending them.

‘`ssmaddmn4`’
  Like `madd` m n `4`, but all involved operations must be signed-saturating.

‘`usmaddmn4`’
  Like `umadd` m n `4`, but all involved operations must be unsigned-saturating.

‘`msubmn4`’
  Multiply operands 1 and 2, sign-extend them to mode n, subtract the result from operand 3, and store the result in operand 0. Operands 1 and 2 have mode m and operands 0 and 3 have mode n. Both modes must be integer or fixed-point modes and n must be twice the size of m.

  In other words, `msub` m n `4` is like `mul` m n `3` except that it also subtracts the result from operand 3.

  These instructions are not allowed to `FAIL`.

‘`umsubmn4`’
  Like `msub` m n `4`, but zero-extend the multiplication operands instead of sign-extending them.

‘`ssmsubmn4`’
  Like `msub` m n `4`, but all involved operations must be signed-saturating.

‘`usmsubmn4`’
  Like `umsub` m n `4`, but all involved operations must be unsigned-saturating.

‘`divmodm4`’
  Signed division that produces both a quotient and a remainder. Operand 1 is divided by operand 2 to produce a quotient stored in operand 0 and a remainder stored in operand 3.

  For machines with an instruction that produces both a quotient and a remainder, provide a pattern for ‘`divmodm4`’ but do not provide patterns for ‘`divm3`’ and ‘`modm3`’. This allows optimization in the relatively common case when both the quotient and remainder are computed.

  If an instruction that just produces a quotient or just a remainder exists and is more efficient than the instruction that produces both, write the output routine of ‘`divmodm4`’ to call `find_reg_note` and look for a `REG_UNUSED` note on the quotient or remainder and generate the appropriate instruction.

‘`udivmodm4`’
  Similar, but does unsigned division.

‘`ashlm3`’, ‘`ssashlm3`’, ‘`usashlm3`’
  Arithmetic-shift operand 1 left by a number of bits specified by operand 2, and store the result in operand 0. Here m is the mode of operand 0 and operand 1; operand 2's mode is specified by the instruction pattern, and the compiler will convert the operand to that mode before generating the instruction. The meaning of out-of-range shift counts can optionally be specified by `TARGET_SHIFT_TRUNCATION_MASK`. See TARGET_SHIFT_TRUNCATION_MASK. Operand 2 is always a scalar type.

‘`ashrm3`’, ‘`lshrm3`’, ‘`rotlm3`’, ‘`rotrm3`’
  Other shift and rotate instructions, analogous to the `ashl` m `3` instructions. Operand 2 is always a scalar type.

‘`vashlm3`’, ‘`vashrm3`’, ‘`vlshrm3`’, ‘`vrotlm3`’, ‘`vrotrm3`’
  Vector shift and rotate instructions that take vectors as operand 2 instead of a scalar type.

‘`bswapm2`’
  Reverse the order of bytes of operand 1 and store the result in operand 0.

‘`negm2`’, ‘`ssnegm2`’, ‘`usnegm2`’
  Negate operand 1 and store the result in operand 0.

‘`absm2`’
  Store the absolute value of operand 1 into operand 0.

‘`sqrtm2`’
  Store the square root of operand 1 into operand 0.

  The `sqrt` built-in function of C always uses the mode which corresponds to the C data type `double` and the `sqrtf` built-in function uses the mode which corresponds to the C data type `float`.

‘`fmodm3`’
  Store the remainder of dividing operand 1 by operand 2 into operand 0, rounded towards zero to an integer.

  The `fmod` built-in function of C always uses the mode which corresponds to the C data type `double` and the `fmodf` built-in function uses the mode which corresponds to the C data type `float`.

‘`remainderm3`’
  Store the remainder of dividing operand 1 by operand 2 into operand 0, rounded to the nearest integer.

  The `remainder` built-in function of C always uses the mode which corresponds to the C data type `double` and the `remainderf` built-in function uses the mode which corresponds to the C data type `float`.

‘`cosm2`’
  Store the cosine of operand 1 into operand 0.

  The `cos` built-in function of C always uses the mode which corresponds to the C data type `double` and the `cosf` built-in function uses the mode which corresponds to the C data type `float`.

‘`sinm2`’
  Store the sine of operand 1 into operand 0.

  The `sin` built-in function of C always uses the mode which corresponds to the C data type `double` and the `sinf` built-in function uses the mode which corresponds to the C data type `float`.

‘`sincosm3`’
  Store the cosine of operand 2 into operand 0 and the sine of operand 2 into operand 1.

  The `sin` and `cos` built-in functions of C always use the mode which corresponds to the C data type `double` and the `sinf` and `cosf` built-in function use the mode which corresponds to the C data type `float`. Targets that can calculate the sine and cosine simultaneously can implement this pattern as opposed to implementing individual `sin` m `2` and `cos` m `2` patterns. The `sin` and `cos` built-in functions will then be expanded to the `sincos` m `3` pattern, with one of the output values left unused.

‘`expm2`’
  Store the exponential of operand 1 into operand 0.

  The `exp` built-in function of C always uses the mode which corresponds to the C data type `double` and the `expf` built-in function uses the mode which corresponds to the C data type `float`.

‘`logm2`’
  Store the natural logarithm of operand 1 into operand 0.

  The `log` built-in function of C always uses the mode which corresponds to the C data type `double` and the `logf` built-in function uses the mode which corresponds to the C data type `float`.

‘`powm3`’
  Store the value of operand 1 raised to the exponent operand 2 into operand 0.

  The `pow` built-in function of C always uses the mode which corresponds to the C data type `double` and the `powf` built-in function uses the mode which corresponds to the C data type `float`.

‘`atan2m3`’
  Store the arc tangent (inverse tangent) of operand 1 divided by operand 2 into operand 0, using the signs of both arguments to determine the quadrant of the result.

  The `atan2` built-in function of C always uses the mode which corresponds to the C data type `double` and the `atan2f` built-in function uses the mode which corresponds to the C data type `float`.

‘`floorm2`’
  Store the largest integral value not greater than argument.

  The `floor` built-in function of C always uses the mode which corresponds to the C data type `double` and the `floorf` built-in function uses the mode which corresponds to the C data type `float`.

‘`btruncm2`’
  Store the argument rounded to integer towards zero.

  The `trunc` built-in function of C always uses the mode which corresponds to the C data type `double` and the `truncf` built-in function uses the mode which corresponds to the C data type `float`.

‘`roundm2`’
  Store the argument rounded to integer away from zero.

  The `round` built-in function of C always uses the mode which corresponds to the C data type `double` and the `roundf` built-in function uses the mode which corresponds to the C data type `float`.

‘`ceilm2`’
  Store the argument rounded to integer away from zero.

  The `ceil` built-in function of C always uses the mode which corresponds to the C data type `double` and the `ceilf` built-in function uses the mode which corresponds to the C data type `float`.

‘`nearbyintm2`’
  Store the argument rounded according to the default rounding mode

  The `nearbyint` built-in function of C always uses the mode which corresponds to the C data type `double` and the `nearbyintf` built-in function uses the mode which corresponds to the C data type `float`.

‘`rintm2`’
  Store the argument rounded according to the default rounding mode and raise the inexact exception when the result differs in value from the argument

  The `rint` built-in function of C always uses the mode which corresponds to the C data type `double` and the `rintf` built-in function uses the mode which corresponds to the C data type `float`.

‘`lrintmn2`’
  Convert operand 1 (valid for floating point mode m) to fixed point mode n as a signed number according to the current rounding mode and store in operand 0 (which has mode n).

‘`lroundmn2`’
  Convert operand 1 (valid for floating point mode m) to fixed point mode n as a signed number rounding to nearest and away from zero and store in operand 0 (which has mode n).

‘`lfloormn2`’
  Convert operand 1 (valid for floating point mode m) to fixed point mode n as a signed number rounding down and store in operand 0 (which has mode n).

‘`lceilmn2`’
  Convert operand 1 (valid for floating point mode m) to fixed point mode n as a signed number rounding up and store in operand 0 (which has mode n).

‘`copysignm3`’
  Store a value with the magnitude of operand 1 and the sign of operand 2 into operand 0.

  The `copysign` built-in function of C always uses the mode which corresponds to the C data type `double` and the `copysignf` built-in function uses the mode which corresponds to the C data type `float`.

‘`ffsm2`’
  Store into operand 0 one plus the index of the least significant 1-bit of operand 1. If operand 1 is zero, store zero. m is the mode of operand 0; operand 1's mode is specified by the instruction pattern, and the compiler will convert the operand to that mode before generating the instruction.

  The `ffs` built-in function of C always uses the mode which corresponds to the C data type `int`.

‘`clzm2`’
  Store into operand 0 the number of leading 0-bits in x, starting at the most significant bit position. If x is 0, the `CLZ_DEFINED_VALUE_AT_ZERO` (see Misc) macro defines if the result is undefined or has a useful value. m is the mode of operand 0; operand 1's mode is specified by the instruction pattern, and the compiler will convert the operand to that mode before generating the instruction.

‘`ctzm2`’
  Store into operand 0 the number of trailing 0-bits in x, starting at the least significant bit position. If x is 0, the `CTZ_DEFINED_VALUE_AT_ZERO` (see Misc) macro defines if the result is undefined or has a useful value. m is the mode of operand 0; operand 1's mode is specified by the instruction pattern, and the compiler will convert the operand to that mode before generating the instruction.

‘`popcountm2`’
  Store into operand 0 the number of 1-bits in x. m is the mode of operand 0; operand 1's mode is specified by the instruction pattern, and the compiler will convert the operand to that mode before generating the instruction.

‘`paritym2`’
  Store into operand 0 the parity of x, i.e. the number of 1-bits in x modulo 2. m is the mode of operand 0; operand 1's mode is specified by the instruction pattern, and the compiler will convert the operand to that mode before generating the instruction.

‘`one_cmplm2`’
  Store the bitwise-complement of operand 1 into operand 0.

‘`movmemm`’
  Block move instruction. The destination and source blocks of memory are the first two operands, and both are `mem:BLK`s with an address in mode `Pmode`.

  The number of bytes to move is the third operand, in mode m. Usually, you specify `Pmode` for m. However, if you can generate better code knowing the range of valid lengths is smaller than those representable in a full Pmode pointer, you should provide a pattern with a mode corresponding to the range of values you can handle efficiently (e.g., `QImode` for values in the range 0–127; note we avoid numbers that appear negative) and also a pattern with `Pmode`.

  The fourth operand is the known shared alignment of the source and destination, in the form of a `const_int` rtx. Thus, if the compiler knows that both source and destination are word-aligned, it may provide the value 4 for this operand.

  Optional operands 5 and 6 specify expected alignment and size of block respectively. The expected alignment differs from alignment in operand 4 in a way that the blocks are not required to be aligned according to it in all cases. This expected alignment is also in bytes, just like operand 4. Expected size, when unknown, is set to `(const_int -1)`.

  Descriptions of multiple `movmem` m patterns can only be beneficial if the patterns for smaller modes have fewer restrictions on their first, second and fourth operands. Note that the mode m in `movmem` m does not impose any restriction on the mode of individually moved data units in the block.

  These patterns need not give special consideration to the possibility that the source and destination strings might overlap.

‘`movstr`’
  String copy instruction, with `stpcpy` semantics. Operand 0 is an output operand in mode `Pmode`. The addresses of the destination and source strings are operands 1 and 2, and both are `mem:BLK`s with addresses in mode `Pmode`. The execution of the expansion of this pattern should store in operand 0 the address in which the `NUL` terminator was stored in the destination string.

  This patern has also several optional operands that are same as in `setmem`.

‘`setmemm`’
  Block set instruction. The destination string is the first operand, given as a `mem:BLK` whose address is in mode `Pmode`. The number of bytes to set is the second operand, in mode m. The value to initialize the memory with is the third operand. Targets that only support the clearing of memory should reject any value that is not the constant 0. See ‘`movmemm`’ for a discussion of the choice of mode.

  The fourth operand is the known alignment of the destination, in the form of a `const_int` rtx. Thus, if the compiler knows that the destination is word-aligned, it may provide the value 4 for this operand.

  Optional operands 5 and 6 specify expected alignment and size of block respectively. The expected alignment differs from alignment in operand 4 in a way that the blocks are not required to be aligned according to it in all cases. This expected alignment is also in bytes, just like operand 4. Expected size, when unknown, is set to `(const_int -1)`. Operand 7 is the minimal size of the block and operand 8 is the maximal size of the block (NULL if it can not be represented as CONST_INT). Operand 9 is the probable maximal size (i.e. we can not rely on it for correctness, but it can be used for choosing proper code sequence for a given size).

  The use for multiple `setmem` m is as for `movmem` m.

‘`cmpstrnm`’
  String compare instruction, with five operands. Operand 0 is the output; it has mode m. The remaining four operands are like the operands of ‘`movmemm`’. The two memory blocks specified are compared byte by byte in lexicographic order starting at the beginning of each string. The instruction is not allowed to prefetch more than one byte at a time since either string may end in the first byte and reading past that may access an invalid page or segment and cause a fault. The comparison terminates early if the fetched bytes are different or if they are equal to zero. The effect of the instruction is to store a value in operand 0 whose sign indicates the result of the comparison.

‘`cmpstrm`’
  String compare instruction, without known maximum length. Operand 0 is the output; it has mode m. The second and third operand are the blocks of memory to be compared; both are `mem:BLK` with an address in mode `Pmode`.

  The fourth operand is the known shared alignment of the source and destination, in the form of a `const_int` rtx. Thus, if the compiler knows that both source and destination are word-aligned, it may provide the value 4 for this operand.

  The two memory blocks specified are compared byte by byte in lexicographic order starting at the beginning of each string. The instruction is not allowed to prefetch more than one byte at a time since either string may end in the first byte and reading past that may access an invalid page or segment and cause a fault. The comparison will terminate when the fetched bytes are different or if they are equal to zero. The effect of the instruction is to store a value in operand 0 whose sign indicates the result of the comparison.

‘`cmpmemm`’
  Block compare instruction, with five operands like the operands of ‘`cmpstrm`’. The two memory blocks specified are compared byte by byte in lexicographic order starting at the beginning of each block. Unlike ‘`cmpstrm`’ the instruction can prefetch any bytes in the two memory blocks. Also unlike ‘`cmpstrm`’ the comparison will not stop if both bytes are zero. The effect of the instruction is to store a value in operand 0 whose sign indicates the result of the comparison.

‘`strlenm`’
  Compute the length of a string, with three operands. Operand 0 is the result (of mode m), operand 1 is a `mem` referring to the first character of the string, operand 2 is the character to search for (normally zero), and operand 3 is a constant describing the known alignment of the beginning of the string.

‘`floatmn2`’
  Convert signed integer operand 1 (valid for fixed point mode m) to floating point mode n and store in operand 0 (which has mode n).

‘`floatunsmn2`’
  Convert unsigned integer operand 1 (valid for fixed point mode m) to floating point mode n and store in operand 0 (which has mode n).

‘`fixmn2`’
  Convert operand 1 (valid for floating point mode m) to fixed point mode n as a signed number and store in operand 0 (which has mode n). This instruction's result is defined only when the value of operand 1 is an integer.

  If the machine description defines this pattern, it also needs to define the `ftrunc` pattern.

‘`fixunsmn2`’
  Convert operand 1 (valid for floating point mode m) to fixed point mode n as an unsigned number and store in operand 0 (which has mode n). This instruction's result is defined only when the value of operand 1 is an integer.

‘`ftruncm2`’
  Convert operand 1 (valid for floating point mode m) to an integer value, still represented in floating point mode m, and store it in operand 0 (valid for floating point mode m).

‘`fix_truncmn2`’
  Like ‘`fixmn2`’ but works for any floating point value of mode m by converting the value to an integer.

‘`fixuns_truncmn2`’
  Like ‘`fixunsmn2`’ but works for any floating point value of mode m by converting the value to an integer.

‘`truncmn2`’
  Truncate operand 1 (valid for mode m) to mode n and store in operand 0 (which has mode n). Both modes must be fixed point or both floating point.

‘`extendmn2`’
  Sign-extend operand 1 (valid for mode m) to mode n and store in operand 0 (which has mode n). Both modes must be fixed point or both floating point.

‘`zero_extendmn2`’
  Zero-extend operand 1 (valid for mode m) to mode n and store in operand 0 (which has mode n). Both modes must be fixed point.

‘`fractmn2`’
  Convert operand 1 of mode m to mode n and store in operand 0 (which has mode n). Mode m and mode n could be fixed-point to fixed-point, signed integer to fixed-point, fixed-point to signed integer, floating-point to fixed-point, or fixed-point to floating-point. When overflows or underflows happen, the results are undefined.

‘`satfractmn2`’
  Convert operand 1 of mode m to mode n and store in operand 0 (which has mode n). Mode m and mode n could be fixed-point to fixed-point, signed integer to fixed-point, or floating-point to fixed-point. When overflows or underflows happen, the instruction saturates the results to the maximum or the minimum.

‘`fractunsmn2`’
  Convert operand 1 of mode m to mode n and store in operand 0 (which has mode n). Mode m and mode n could be unsigned integer to fixed-point, or fixed-point to unsigned integer. When overflows or underflows happen, the results are undefined.

‘`satfractunsmn2`’
  Convert unsigned integer operand 1 of mode m to fixed-point mode n and store in operand 0 (which has mode n). When overflows or underflows happen, the instruction saturates the results to the maximum or the minimum.

‘`extvm`’
  Extract a bit-field from register operand 1, sign-extend it, and store it in operand 0. Operand 2 specifies the width of the field in bits and operand 3 the starting bit, which counts from the most significant bit if ‘`BITS_BIG_ENDIAN`’ is true and from the least significant bit otherwise.

  Operands 0 and 1 both have mode m. Operands 2 and 3 have a target-specific mode.

‘`extvmisalignm`’
  Extract a bit-field from memory operand 1, sign extend it, and store it in operand 0. Operand 2 specifies the width in bits and operand 3 the starting bit. The starting bit is always somewhere in the first byte of operand 1; it counts from the most significant bit if ‘`BITS_BIG_ENDIAN`’ is true and from the least significant bit otherwise.

  Operand 0 has mode m while operand 1 has `BLK` mode. Operands 2 and 3 have a target-specific mode.

  The instruction must not read beyond the last byte of the bit-field.

‘`extzvm`’
  Like ‘`extvm`’ except that the bit-field value is zero-extended.

‘`extzvmisalignm`’
  Like ‘`extvmisalignm`’ except that the bit-field value is zero-extended.

‘`insvm`’
  Insert operand 3 into a bit-field of register operand 0. Operand 1 specifies the width of the field in bits and operand 2 the starting bit, which counts from the most significant bit if ‘`BITS_BIG_ENDIAN`’ is true and from the least significant bit otherwise.

  Operands 0 and 3 both have mode m. Operands 1 and 2 have a target-specific mode.

‘`insvmisalignm`’
  Insert operand 3 into a bit-field of memory operand 0. Operand 1 specifies the width of the field in bits and operand 2 the starting bit. The starting bit is always somewhere in the first byte of operand 0; it counts from the most significant bit if ‘`BITS_BIG_ENDIAN`’ is true and from the least significant bit otherwise.

  Operand 3 has mode m while operand 0 has `BLK` mode. Operands 1 and 2 have a target-specific mode.

  The instruction must not read or write beyond the last byte of the bit-field.

‘`extv`’
  Extract a bit-field from operand 1 (a register or memory operand), where operand 2 specifies the width in bits and operand 3 the starting bit, and store it in operand 0. Operand 0 must have mode `word_mode`. Operand 1 may have mode `byte_mode` or `word_mode`; often `word_mode` is allowed only for registers. Operands 2 and 3 must be valid for `word_mode`.

  The RTL generation pass generates this instruction only with constants for operands 2 and 3 and the constant is never zero for operand 2.

  The bit-field value is sign-extended to a full word integer before it is stored in operand 0.

  This pattern is deprecated; please use ‘`extvm`’ and `extvmisalign` m instead.

‘`extzv`’
  Like ‘`extv`’ except that the bit-field value is zero-extended.

  This pattern is deprecated; please use ‘`extzvm`’ and `extzvmisalign` m instead.

‘`insv`’
  Store operand 3 (which must be valid for `word_mode`) into a bit-field in operand 0, where operand 1 specifies the width in bits and operand 2 the starting bit. Operand 0 may have mode `byte_mode` or `word_mode`; often `word_mode` is allowed only for registers. Operands 1 and 2 must be valid for `word_mode`.

  The RTL generation pass generates this instruction only with constants for operands 1 and 2 and the constant is never zero for operand 1.

  This pattern is deprecated; please use ‘`insvm`’ and `insvmisalign` m instead.

‘`movmodecc`’
  Conditionally move operand 2 or operand 3 into operand 0 according to the comparison in operand 1. If the comparison is true, operand 2 is moved into operand 0, otherwise operand 3 is moved.

  The mode of the operands being compared need not be the same as the operands being moved. Some machines, sparc64 for example, have instructions that conditionally move an integer value based on the floating point condition codes and vice versa.

  If the machine does not have conditional move instructions, do not define these patterns.

‘`addmodecc`’
  Similar to ‘`movmodecc`’ but for conditional addition. Conditionally move operand 2 or (operands 2 + operand 3) into operand 0 according to the comparison in operand 1. If the comparison is false, operand 2 is moved into operand 0, otherwise (operand 2 + operand 3) is moved.

‘`cstoremode4`’
  Store zero or nonzero in operand 0 according to whether a comparison is true. Operand 1 is a comparison operator. Operand 2 and operand 3 are the first and second operand of the comparison, respectively. You specify the mode that operand 0 must have when you write the `match_operand` expression. The compiler automatically sees which mode you have used and supplies an operand of that mode.

  The value stored for a true condition must have 1 as its low bit, or else must be negative. Otherwise the instruction is not suitable and you should omit it from the machine description. You describe to the compiler exactly which value is stored by defining the macro `STORE_FLAG_VALUE` (see Misc). If a description cannot be found that can be used for all the possible comparison operators, you should pick one and use a `define_expand` to map all results onto the one you chose.

  These operations may `FAIL`, but should do so only in relatively uncommon cases; if they would `FAIL` for common cases involving integer comparisons, it is best to restrict the predicates to not allow these operands. Likewise if a given comparison operator will always fail, independent of the operands (for floating-point modes, the `ordered_comparison_operator` predicate is often useful in this case).

  If this pattern is omitted, the compiler will generate a conditional branch—for example, it may copy a constant one to the target and branching around an assignment of zero to the target—or a libcall. If the predicate for operand 1 only rejects some operators, it will also try reordering the operands and/or inverting the result value (e.g. by an exclusive OR). These possibilities could be cheaper or equivalent to the instructions used for the ‘`cstoremode4`’ pattern followed by those required to convert a positive result from `STORE_FLAG_VALUE` to 1; in this case, you can and should make operand 1's predicate reject some operators in the ‘`cstoremode4`’ pattern, or remove the pattern altogether from the machine description.

‘`cbranchmode4`’
  Conditional branch instruction combined with a compare instruction. Operand 0 is a comparison operator. Operand 1 and operand 2 are the first and second operands of the comparison, respectively. Operand 3 is a `label_ref` that refers to the label to jump to.

‘`jump`’
  A jump inside a function; an unconditional branch. Operand 0 is the `label_ref` of the label to jump to. This pattern name is mandatory on all machines.

‘`call`’
  Subroutine call instruction returning no value. Operand 0 is the function to call; operand 1 is the number of bytes of arguments pushed as a `const_int`; operand 2 is the number of registers used as operands.

  On most machines, operand 2 is not actually stored into the RTL pattern. It is supplied for the sake of some RISC machines which need to put this information into the assembler code; they can put it in the RTL instead of operand 1.

  Operand 0 should be a `mem` RTX whose address is the address of the function. Note, however, that this address can be a `symbol_ref` expression even if it would not be a legitimate memory address on the target machine. If it is also not a valid argument for a call instruction, the pattern for this operation should be a `define_expand` (see Expander Definitions) that places the address into a register and uses that register in the call instruction.

‘`call_value`’
  Subroutine call instruction returning a value. Operand 0 is the hard register in which the value is returned. There are three more operands, the same as the three operands of the ‘`call`’ instruction (but with numbers increased by one).

  Subroutines that return `BLKmode` objects use the ‘`call`’ insn.

‘`call_pop`’, ‘`call_value_pop`’
  Similar to ‘`call`’ and ‘`call_value`’, except used if defined and if `RETURN_POPS_ARGS` is nonzero. They should emit a `parallel` that contains both the function call and a `set` to indicate the adjustment made to the frame pointer.

  For machines where `RETURN_POPS_ARGS` can be nonzero, the use of these patterns increases the number of functions for which the frame pointer can be eliminated, if desired.

‘`untyped_call`’
  Subroutine call instruction returning a value of any type. Operand 0 is the function to call; operand 1 is a memory location where the result of calling the function is to be stored; operand 2 is a `parallel` expression where each element is a `set` expression that indicates the saving of a function return value into the result block.

  This instruction pattern should be defined to support `__builtin_apply` on machines where special instructions are needed to call a subroutine with arbitrary arguments or to save the value returned. This instruction pattern is required on machines that have multiple registers that can hold a return value (i.e. `FUNCTION_VALUE_REGNO_P` is true for more than one register).

‘`return`’
  Subroutine return instruction. This instruction pattern name should be defined only if a single instruction can do all the work of returning from a function.

  Like the ‘`movm`’ patterns, this pattern is also used after the RTL generation phase. In this case it is to support machines where multiple instructions are usually needed to return from a function, but some class of functions only requires one instruction to implement a return. Normally, the applicable functions are those which do not need to save any registers or allocate stack space.

  It is valid for this pattern to expand to an instruction using `simple_return` if no epilogue is required.

‘`simple_return`’
  Subroutine return instruction. This instruction pattern name should be defined only if a single instruction can do all the work of returning from a function on a path where no epilogue is required. This pattern is very similar to the `return` instruction pattern, but it is emitted only by the shrink-wrapping optimization on paths where the function prologue has not been executed, and a function return should occur without any of the effects of the epilogue. Additional uses may be introduced on paths where both the prologue and the epilogue have executed.

  For such machines, the condition specified in this pattern should only be true when `reload_completed` is nonzero and the function's epilogue would only be a single instruction. For machines with register windows, the routine `leaf_function_p` may be used to determine if a register window push is required.

  Machines that have conditional return instructions should define patterns such as

                (define_insn ""
                  [(set (pc)
                        (if_then_else (match_operator
                                         0 "comparison_operator"
                                         [(cc0) (const_int 0)])
                                      (return)
                                      (pc)))]
                  "condition"
                  "...")

  where condition would normally be the same condition specified on the named ‘`return`’ pattern.

‘`untyped_return`’
  Untyped subroutine return instruction. This instruction pattern should be defined to support `__builtin_return` on machines where special instructions are needed to return a value of any type.

  Operand 0 is a memory location where the result of calling a function with `__builtin_apply` is stored; operand 1 is a `parallel` expression where each element is a `set` expression that indicates the restoring of a function return value from the result block.

‘`nop`’
  No-op instruction. This instruction pattern name should always be defined to output a no-op in assembler code. `(const_int 0)` will do as an RTL pattern.

‘`indirect_jump`’
  An instruction to jump to an address which is operand zero. This pattern name is mandatory on all machines.

‘`casesi`’
  Instruction to jump through a dispatch table, including bounds checking. This instruction takes five operands:
  1. The index to dispatch on, which has mode `SImode`.
  2. The lower bound for indices in the table, an integer constant.
  3. The total range of indices in the table—the largest index minus the smallest one (both inclusive).
  4. A label that precedes the table itself.
  5. A label to jump to if the index has a value outside the bounds.

  The table is an `addr_vec` or `addr_diff_vec` inside of a `jump_table_data`. The number of elements in the table is one plus the difference between the upper bound and the lower bound.

‘`tablejump`’
  Instruction to jump to a variable address. This is a low-level capability which can be used to implement a dispatch table when there is no ‘`casesi`’ pattern.

  This pattern requires two operands: the address or offset, and a label which should immediately precede the jump table. If the macro `CASE_VECTOR_PC_RELATIVE` evaluates to a nonzero value then the first operand is an offset which counts from the address of the table; otherwise, it is an absolute address to jump to. In either case, the first operand has mode `Pmode`.

  The ‘`tablejump`’ insn is always the last insn before the jump table it uses. Its assembler code normally has no need to use the second operand, but you should incorporate it in the RTL pattern so that the jump optimizer will not delete the table as unreachable code.

‘`decrement_and_branch_until_zero`’
  Conditional branch instruction that decrements a register and jumps if the register is nonzero. Operand 0 is the register to decrement and test; operand 1 is the label to jump to if the register is nonzero. See Looping Patterns.

  This optional instruction pattern is only used by the combiner, typically for loops reversed by the loop optimizer when strength reduction is enabled.

‘`doloop_end`’
  Conditional branch instruction that decrements a register and jumps if the register is nonzero. Operand 0 is the register to decrement and test; operand 1 is the label to jump to if the register is nonzero. See Looping Patterns.

  This optional instruction pattern should be defined for machines with low-overhead looping instructions as the loop optimizer will try to modify suitable loops to utilize it. The target hook `TARGET_CAN_USE_DOLOOP_P` controls the conditions under which low-overhead loops can be used.

‘`doloop_begin`’
  Companion instruction to `doloop_end` required for machines that need to perform some initialization, such as loading a special counter register. Operand 1 is the associated `doloop_end` pattern and operand 0 is the register that it decrements.

  If initialization insns do not always need to be emitted, use a `define_expand` (see Expander Definitions) and make it fail.

‘`canonicalize_funcptr_for_compare`’
  Canonicalize the function pointer in operand 1 and store the result into operand 0.

  Operand 0 is always a `reg` and has mode `Pmode`; operand 1 may be a `reg`, `mem`, `symbol_ref`, `const_int`, etc and also has mode `Pmode`.

  Canonicalization of a function pointer usually involves computing the address of the function which would be called if the function pointer were used in an indirect call.

  Only define this pattern if function pointers on the target machine can have different values but still call the same function when used in an indirect call.

‘`save_stack_block`’
‘`save_stack_function`’
‘`save_stack_nonlocal`’
‘`restore_stack_block`’
‘`restore_stack_function`’
‘`restore_stack_nonlocal`’
  Most machines save and restore the stack pointer by copying it to or from an object of mode `Pmode`. Do not define these patterns on such machines.

  Some machines require special handling for stack pointer saves and restores. On those machines, define the patterns corresponding to the non-standard cases by using a `define_expand` (see Expander Definitions) that produces the required insns. The three types of saves and restores are:

  1. ‘`save_stack_block`’ saves the stack pointer at the start of a block that allocates a variable-sized object, and ‘`restore_stack_block`’ restores the stack pointer when the block is exited.
  2. ‘`save_stack_function`’ and ‘`restore_stack_function`’ do a similar job for the outermost block of a function and are used when the function allocates variable-sized objects or calls `alloca`. Only the epilogue uses the restored stack pointer, allowing a simpler save or restore sequence on some machines.
  3. ‘`save_stack_nonlocal`’ is used in functions that contain labels branched to by nested functions. It saves the stack pointer in such a way that the inner function can use ‘`restore_stack_nonlocal`’ to restore the stack pointer. The compiler generates code to restore the frame and argument pointer registers, but some machines require saving and restoring additional data such as register window information or stack backchains. Place insns in these patterns to save and restore any such required data.

  When saving the stack pointer, operand 0 is the save area and operand 1 is the stack pointer. The mode used to allocate the save area defaults to `Pmode` but you can override that choice by defining the `STACK_SAVEAREA_MODE` macro (see Storage Layout). You must specify an integral mode, or `VOIDmode` if no save area is needed for a particular type of save (either because no save is needed or because a machine-specific save area can be used). Operand 0 is the stack pointer and operand 1 is the save area for restore operations. If ‘`save_stack_block`’ is defined, operand 0 must not be `VOIDmode` since these saves can be arbitrarily nested.

  A save area is a `mem` that is at a constant offset from `virtual_stack_vars_rtx` when the stack pointer is saved for use by nonlocal gotos and a `reg` in the other two cases.

‘`allocate_stack`’
  Subtract (or add if `STACK_GROWS_DOWNWARD` is undefined) operand 1 from the stack pointer to create space for dynamically allocated data.

  Store the resultant pointer to this space into operand 0. If you are allocating space from the main stack, do this by emitting a move insn to copy `virtual_stack_dynamic_rtx` to operand 0. If you are allocating the space elsewhere, generate code to copy the location of the space to operand 0. In the latter case, you must ensure this space gets freed when the corresponding space on the main stack is free.

  Do not define this pattern if all that must be done is the subtraction. Some machines require other operations such as stack probes or maintaining the back chain. Define this pattern to emit those operations in addition to updating the stack pointer.

‘`check_stack`’
  If stack checking (see Stack Checking) cannot be done on your system by probing the stack, define this pattern to perform the needed check and signal an error if the stack has overflowed. The single operand is the address in the stack farthest from the current stack pointer that you need to validate. Normally, on platforms where this pattern is needed, you would obtain the stack limit from a global or thread-specific variable or register.

‘`probe_stack_address`’
  If stack checking (see Stack Checking) can be done on your system by probing the stack but without the need to actually access it, define this pattern and signal an error if the stack has overflowed. The single operand is the memory address in the stack that needs to be probed.

‘`probe_stack`’
  If stack checking (see Stack Checking) can be done on your system by probing the stack but doing it with a “store zero” instruction is not valid or optimal, define this pattern to do the probing differently and signal an error if the stack has overflowed. The single operand is the memory reference in the stack that needs to be probed.

‘`nonlocal_goto`’
  Emit code to generate a non-local goto, e.g., a jump from one function to a label in an outer function. This pattern has four arguments, each representing a value to be used in the jump. The first argument is to be loaded into the frame pointer, the second is the address to branch to (code to dispatch to the actual label), the third is the address of a location where the stack is saved, and the last is the address of the label, to be placed in the location for the incoming static chain.

  On most machines you need not define this pattern, since GCC will already generate the correct code, which is to load the frame pointer and static chain, restore the stack (using the ‘`restore_stack_nonlocal`’ pattern, if defined), and jump indirectly to the dispatcher. You need only define this pattern if this code will not work on your machine.

‘`nonlocal_goto_receiver`’
  This pattern, if defined, contains code needed at the target of a nonlocal goto after the code already generated by GCC. You will not normally need to define this pattern. A typical reason why you might need this pattern is if some value, such as a pointer to a global table, must be restored when the frame pointer is restored. Note that a nonlocal goto only occurs within a unit-of-translation, so a global table pointer that is shared by all functions of a given module need not be restored. There are no arguments.

‘`exception_receiver`’
  This pattern, if defined, contains code needed at the site of an exception handler that isn't needed at the site of a nonlocal goto. You will not normally need to define this pattern. A typical reason why you might need this pattern is if some value, such as a pointer to a global table, must be restored after control flow is branched to the handler of an exception. There are no arguments.

‘`builtin_setjmp_setup`’
  This pattern, if defined, contains additional code needed to initialize the `jmp_buf`. You will not normally need to define this pattern. A typical reason why you might need this pattern is if some value, such as a pointer to a global table, must be restored. Though it is preferred that the pointer value be recalculated if possible (given the address of a label for instance). The single argument is a pointer to the `jmp_buf`. Note that the buffer is five words long and that the first three are normally used by the generic mechanism.

‘`builtin_setjmp_receiver`’
  This pattern, if defined, contains code needed at the site of a built-in setjmp that isn't needed at the site of a nonlocal goto. You will not normally need to define this pattern. A typical reason why you might need this pattern is if some value, such as a pointer to a global table, must be restored. It takes one argument, which is the label to which builtin_longjmp transferred control; this pattern may be emitted at a small offset from that label.

‘`builtin_longjmp`’
  This pattern, if defined, performs the entire action of the longjmp. You will not normally need to define this pattern unless you also define `builtin_setjmp_setup`. The single argument is a pointer to the `jmp_buf`.

‘`eh_return`’
  This pattern, if defined, affects the way `__builtin_eh_return`, and thence the call frame exception handling library routines, are built. It is intended to handle non-trivial actions needed along the abnormal return path.

  The address of the exception handler to which the function should return is passed as operand to this pattern. It will normally need to copied by the pattern to some special register or memory location. If the pattern needs to determine the location of the target call frame in order to do so, it may use `EH_RETURN_STACKADJ_RTX`, if defined; it will have already been assigned.

  If this pattern is not defined, the default action will be to simply copy the return address to `EH_RETURN_HANDLER_RTX`. Either that macro or this pattern needs to be defined if call frame exception handling is to be used.

‘`prologue`’
  This pattern, if defined, emits RTL for entry to a function. The function entry is responsible for setting up the stack frame, initializing the frame pointer register, saving callee saved registers, etc.

  Using a prologue pattern is generally preferred over defining `TARGET_ASM_FUNCTION_PROLOGUE` to emit assembly code for the prologue.

  The `prologue` pattern is particularly useful for targets which perform instruction scheduling.

‘`window_save`’
  This pattern, if defined, emits RTL for a register window save. It should be defined if the target machine has register windows but the window events are decoupled from calls to subroutines. The canonical example is the SPARC architecture.

‘`epilogue`’
  This pattern emits RTL for exit from a function. The function exit is responsible for deallocating the stack frame, restoring callee saved registers and emitting the return instruction.

  Using an epilogue pattern is generally preferred over defining `TARGET_ASM_FUNCTION_EPILOGUE` to emit assembly code for the epilogue.

  The `epilogue` pattern is particularly useful for targets which perform instruction scheduling or which have delay slots for their return instruction.

‘`sibcall_epilogue`’
  This pattern, if defined, emits RTL for exit from a function without the final branch back to the calling function. This pattern will be emitted before any sibling call (aka tail call) sites.

  The `sibcall_epilogue` pattern must not clobber any arguments used for parameter passing or any stack slots for arguments passed to the current function.

‘`trap`’
  This pattern, if defined, signals an error, typically by causing some kind of signal to be raised. Among other places, it is used by the Java front end to signal `invalid array index' exceptions.

‘`ctrapMM4`’
  Conditional trap instruction. Operand 0 is a piece of RTL which performs a comparison, and operands 1 and 2 are the arms of the comparison. Operand 3 is the trap code, an integer.

  A typical `ctrap` pattern looks like

                (define_insn "ctrapsi4"
                  [(trap_if (match_operator 0 "trap_operator"
                             [(match_operand 1 "register_operand")
                              (match_operand 2 "immediate_operand")])
                            (match_operand 3 "const_int_operand" "i"))]
                  ""
                  "...")

‘`prefetch`’
  This pattern, if defined, emits code for a non-faulting data prefetch instruction. Operand 0 is the address of the memory to prefetch. Operand 1 is a constant 1 if the prefetch is preparing for a write to the memory address, or a constant 0 otherwise. Operand 2 is the expected degree of temporal locality of the data and is a value between 0 and 3, inclusive; 0 means that the data has no temporal locality, so it need not be left in the cache after the access; 3 means that the data has a high degree of temporal locality and should be left in all levels of cache possible; 1 and 2 mean, respectively, a low or moderate degree of temporal locality.

  Targets that do not support write prefetches or locality hints can ignore the values of operands 1 and 2.

‘`blockage`’
  This pattern defines a pseudo insn that prevents the instruction scheduler and other passes from moving instructions and using register equivalences across the boundary defined by the blockage insn. This needs to be an UNSPEC_VOLATILE pattern or a volatile ASM.

‘`memory_barrier`’
  If the target memory model is not fully synchronous, then this pattern should be defined to an instruction that orders both loads and stores before the instruction with respect to loads and stores after the instruction. This pattern has no operands.

‘`sync_compare_and_swapmode`’
  This pattern, if defined, emits code for an atomic compare-and-swap operation. Operand 1 is the memory on which the atomic operation is performed. Operand 2 is the “old” value to be compared against the current contents of the memory location. Operand 3 is the “new” value to store in the memory if the compare succeeds. Operand 0 is the result of the operation; it should contain the contents of the memory before the operation. If the compare succeeds, this should obviously be a copy of operand 2.

  This pattern must show that both operand 0 and operand 1 are modified.

  This pattern must issue any memory barrier instructions such that all memory operations before the atomic operation occur before the atomic operation and all memory operations after the atomic operation occur after the atomic operation.

  For targets where the success or failure of the compare-and-swap operation is available via the status flags, it is possible to avoid a separate compare operation and issue the subsequent branch or store-flag operation immediately after the compare-and-swap. To this end, GCC will look for a `MODE_CC` set in the output of `sync_compare_and_swap` mode; if the machine description includes such a set, the target should also define special `cbranchcc4` and/or `cstorecc4` instructions. GCC will then be able to take the destination of the `MODE_CC` set and pass it to the `cbranchcc4` or `cstorecc4` pattern as the first operand of the comparison (the second will be `(const_int 0)`).

  For targets where the operating system may provide support for this operation via library calls, the `sync_compare_and_swap_optab` may be initialized to a function with the same interface as the `__sync_val_compare_and_swap_`n built-in. If the entire set of __sync builtins are supported via library calls, the target can initialize all of the optabs at once with `init_sync_libfuncs`. For the purposes of C++11 `std::atomic::is_lock_free`, it is assumed that these library calls do not use any kind of interruptable locking.

‘`sync_addmode`’, ‘`sync_submode`’
‘`sync_iormode`’, ‘`sync_andmode`’
‘`sync_xormode`’, ‘`sync_nandmode`’
  These patterns emit code for an atomic operation on memory. Operand 0 is the memory on which the atomic operation is performed. Operand 1 is the second operand to the binary operator.

  This pattern must issue any memory barrier instructions such that all memory operations before the atomic operation occur before the atomic operation and all memory operations after the atomic operation occur after the atomic operation.

  If these patterns are not defined, the operation will be constructed from a compare-and-swap operation, if defined.

‘`sync_old_addmode`’, ‘`sync_old_submode`’
‘`sync_old_iormode`’, ‘`sync_old_andmode`’
‘`sync_old_xormode`’, ‘`sync_old_nandmode`’
  These patterns emit code for an atomic operation on memory, and return the value that the memory contained before the operation. Operand 0 is the result value, operand 1 is the memory on which the atomic operation is performed, and operand 2 is the second operand to the binary operator.

  This pattern must issue any memory barrier instructions such that all memory operations before the atomic operation occur before the atomic operation and all memory operations after the atomic operation occur after the atomic operation.

  If these patterns are not defined, the operation will be constructed from a compare-and-swap operation, if defined.

‘`sync_new_addmode`’, ‘`sync_new_submode`’
‘`sync_new_iormode`’, ‘`sync_new_andmode`’
‘`sync_new_xormode`’, ‘`sync_new_nandmode`’
  These patterns are like their `sync_old_`op counterparts, except that they return the value that exists in the memory location after the operation, rather than before the operation.

‘`sync_lock_test_and_setmode`’
  This pattern takes two forms, based on the capabilities of the target. In either case, operand 0 is the result of the operand, operand 1 is the memory on which the atomic operation is performed, and operand 2 is the value to set in the lock.

  In the ideal case, this operation is an atomic exchange operation, in which the previous value in memory operand is copied into the result operand, and the value operand is stored in the memory operand.

  For less capable targets, any value operand that is not the constant 1 should be rejected with `FAIL`. In this case the target may use an atomic test-and-set bit operation. The result operand should contain 1 if the bit was previously set and 0 if the bit was previously clear. The true contents of the memory operand are implementation defined.

  This pattern must issue any memory barrier instructions such that the pattern as a whole acts as an acquire barrier, that is all memory operations after the pattern do not occur until the lock is acquired.

  If this pattern is not defined, the operation will be constructed from a compare-and-swap operation, if defined.

‘`sync_lock_releasemode`’
  This pattern, if defined, releases a lock set by `sync_lock_test_and_set` mode. Operand 0 is the memory that contains the lock; operand 1 is the value to store in the lock.

  If the target doesn't implement full semantics for `sync_lock_test_and_set` mode, any value operand which is not the constant 0 should be rejected with `FAIL`, and the true contents of the memory operand are implementation defined.

  This pattern must issue any memory barrier instructions such that the pattern as a whole acts as a release barrier, that is the lock is released only after all previous memory operations have completed.

  If this pattern is not defined, then a `memory_barrier` pattern will be emitted, followed by a store of the value to the memory operand.

‘`atomic_compare_and_swapmode`’
  This pattern, if defined, emits code for an atomic compare-and-swap operation with memory model semantics. Operand 2 is the memory on which the atomic operation is performed. Operand 0 is an output operand which is set to true or false based on whether the operation succeeded. Operand 1 is an output operand which is set to the contents of the memory before the operation was attempted. Operand 3 is the value that is expected to be in memory. Operand 4 is the value to put in memory if the expected value is found there. Operand 5 is set to 1 if this compare and swap is to be treated as a weak operation. Operand 6 is the memory model to be used if the operation is a success. Operand 7 is the memory model to be used if the operation fails.

  If memory referred to in operand 2 contains the value in operand 3, then operand 4 is stored in memory pointed to by operand 2 and fencing based on the memory model in operand 6 is issued.

  If memory referred to in operand 2 does not contain the value in operand 3, then fencing based on the memory model in operand 7 is issued.

  If a target does not support weak compare-and-swap operations, or the port elects not to implement weak operations, the argument in operand 5 can be ignored. Note a strong implementation must be provided.

  If this pattern is not provided, the `__atomic_compare_exchange` built-in functions will utilize the legacy `sync_compare_and_swap` pattern with an `__ATOMIC_SEQ_CST` memory model.

‘`atomic_loadmode`’
  This pattern implements an atomic load operation with memory model semantics. Operand 1 is the memory address being loaded from. Operand 0 is the result of the load. Operand 2 is the memory model to be used for the load operation.

  If not present, the `__atomic_load` built-in function will either resort to a normal load with memory barriers, or a compare-and-swap operation if a normal load would not be atomic.

‘`atomic_storemode`’
  This pattern implements an atomic store operation with memory model semantics. Operand 0 is the memory address being stored to. Operand 1 is the value to be written. Operand 2 is the memory model to be used for the operation.

  If not present, the `__atomic_store` built-in function will attempt to perform a normal store and surround it with any required memory fences. If the store would not be atomic, then an `__atomic_exchange` is attempted with the result being ignored.

‘`atomic_exchangemode`’
  This pattern implements an atomic exchange operation with memory model semantics. Operand 1 is the memory location the operation is performed on. Operand 0 is an output operand which is set to the original value contained in the memory pointed to by operand 1. Operand 2 is the value to be stored. Operand 3 is the memory model to be used.

  If this pattern is not present, the built-in function `__atomic_exchange` will attempt to preform the operation with a compare and swap loop.

‘`atomic_addmode`’, ‘`atomic_submode`’
‘`atomic_ormode`’, ‘`atomic_andmode`’
‘`atomic_xormode`’, ‘`atomic_nandmode`’
  These patterns emit code for an atomic operation on memory with memory model semantics. Operand 0 is the memory on which the atomic operation is performed. Operand 1 is the second operand to the binary operator. Operand 2 is the memory model to be used by the operation.

  If these patterns are not defined, attempts will be made to use legacy `sync` patterns, or equivalent patterns which return a result. If none of these are available a compare-and-swap loop will be used.

‘`atomic_fetch_addmode`’, ‘`atomic_fetch_submode`’
‘`atomic_fetch_ormode`’, ‘`atomic_fetch_andmode`’
‘`atomic_fetch_xormode`’, ‘`atomic_fetch_nandmode`’
  These patterns emit code for an atomic operation on memory with memory model semantics, and return the original value. Operand 0 is an output operand which contains the value of the memory location before the operation was performed. Operand 1 is the memory on which the atomic operation is performed. Operand 2 is the second operand to the binary operator. Operand 3 is the memory model to be used by the operation.

  If these patterns are not defined, attempts will be made to use legacy `sync` patterns. If none of these are available a compare-and-swap loop will be used.

‘`atomic_add_fetchmode`’, ‘`atomic_sub_fetchmode`’
‘`atomic_or_fetchmode`’, ‘`atomic_and_fetchmode`’
‘`atomic_xor_fetchmode`’, ‘`atomic_nand_fetchmode`’
  These patterns emit code for an atomic operation on memory with memory model semantics and return the result after the operation is performed. Operand 0 is an output operand which contains the value after the operation. Operand 1 is the memory on which the atomic operation is performed. Operand 2 is the second operand to the binary operator. Operand 3 is the memory model to be used by the operation.

  If these patterns are not defined, attempts will be made to use legacy `sync` patterns, or equivalent patterns which return the result before the operation followed by the arithmetic operation required to produce the result. If none of these are available a compare-and-swap loop will be used.

‘`atomic_test_and_set`’
  This pattern emits code for `__builtin_atomic_test_and_set`. Operand 0 is an output operand which is set to true if the previous previous contents of the byte was "set", and false otherwise. Operand 1 is the `QImode` memory to be modified. Operand 2 is the memory model to be used.

  The specific value that defines "set" is implementation defined, and is normally based on what is performed by the native atomic test and set instruction.

‘`mem_thread_fencemode`’
  This pattern emits code required to implement a thread fence with memory model semantics. Operand 0 is the memory model to be used.

  If this pattern is not specified, all memory models except `__ATOMIC_RELAXED` will result in issuing a `sync_synchronize` barrier pattern.

‘`mem_signal_fencemode`’
  This pattern emits code required to implement a signal fence with memory model semantics. Operand 0 is the memory model to be used.

  This pattern should impact the compiler optimizers the same way that mem_signal_fence does, but it does not need to issue any barrier instructions.

  If this pattern is not specified, all memory models except `__ATOMIC_RELAXED` will result in issuing a `sync_synchronize` barrier pattern.

‘`get_thread_pointermode`’
‘`set_thread_pointermode`’
  These patterns emit code that reads/sets the TLS thread pointer. Currently, these are only needed if the target needs to support the `__builtin_thread_pointer` and `__builtin_set_thread_pointer` builtins.

  The get/set patterns have a single output/input operand respectively, with mode intended to be `Pmode`.

‘`stack_protect_set`’
  This pattern, if defined, moves a `ptr_mode` value from the memory in operand 1 to the memory in operand 0 without leaving the value in a register afterward. This is to avoid leaking the value some place that an attacker might use to rewrite the stack guard slot after having clobbered it.

  If this pattern is not defined, then a plain move pattern is generated.

‘`stack_protect_test`’
  This pattern, if defined, compares a `ptr_mode` value from the memory in operand 1 with the memory in operand 0 without leaving the value in a register afterward and branches to operand 2 if the values were equal.

  If this pattern is not defined, then a plain compare pattern and conditional branch pattern is used.

‘`clear_cache`’
  This pattern, if defined, flushes the instruction cache for a region of memory. The region is bounded to by the Pmode pointers in operand 0 inclusive and operand 1 exclusive.

  If this pattern is not defined, a call to the library function `__clear_cache` is used.