6.31.23 PowerPC Function Attributes

These function attributes are supported by the PowerPC back end:

longcall

shortcall

The longcall attribute indicates that the function might be far away from the call site and require a different (more expensive) calling sequence. The shortcall attribute indicates that the function is always close enough for the shorter calling sequence to be used. These attributes override both the -mlongcall switch and the #pragma longcall setting.

See RS/6000 and PowerPC Options, for more information on whether long calls are necessary.

target (options)

As discussed in Common Function Attributes, this attribute allows specification of target-specific compilation options.

On the PowerPC, the following options are allowed:

‘altivec’

‘no-altivec’

Generate code that uses (does not use) AltiVec instructions. In 32-bit code, you cannot enable AltiVec instructions unless -mabi=altivec is used on the command line.

‘cmpb’

‘no-cmpb’

Generate code that uses (does not use) the compare bytes instruction implemented on the POWER6 processor and other processors that support the PowerPC V2.05 architecture.

‘dlmzb’

‘no-dlmzb’

Generate code that uses (does not use) the string-search ‘dlmzb’ instruction on the IBM 405, 440, 464 and 476 processors. This instruction is generated by default when targeting those processors.

‘fprnd’

‘no-fprnd’

Generate code that uses (does not use) the FP round to integer instructions implemented on the POWER5+ processor and other processors that support the PowerPC V2.03 architecture.

‘hard-dfp’

‘no-hard-dfp’

Generate code that uses (does not use) the decimal floating-point instructions implemented on some POWER processors.

‘isel’

‘no-isel’

Generate code that uses (does not use) ISEL instruction.

‘mfcrf’

‘no-mfcrf’

Generate code that uses (does not use) the move from condition register field instruction implemented on the POWER4 processor and other processors that support the PowerPC V2.01 architecture.

‘mfpgpr’

‘no-mfpgpr’

Generate code that uses (does not use) the FP move to/from general purpose register instructions implemented on the POWER6X processor and other processors that support the extended PowerPC V2.05 architecture.

‘mulhw’

‘no-mulhw’

Generate code that uses (does not use) the half-word multiply and multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors. These instructions are generated by default when targeting those processors.

‘multiple’

‘no-multiple’

Generate code that uses (does not use) the load multiple word instructions and the store multiple word instructions.

‘update’

‘no-update’

Generate code that uses (does not use) the load or store instructions that update the base register to the address of the calculated memory location.

‘popcntb’

‘no-popcntb’

Generate code that uses (does not use) the popcount and double-precision FP reciprocal estimate instruction implemented on the POWER5 processor and other processors that support the PowerPC V2.02 architecture.

‘popcntd’

‘no-popcntd’

Generate code that uses (does not use) the popcount instruction implemented on the POWER7 processor and other processors that support the PowerPC V2.06 architecture.

‘powerpc-gfxopt’

‘no-powerpc-gfxopt’

Generate code that uses (does not use) the optional PowerPC architecture instructions in the Graphics group, including floating-point select.

‘powerpc-gpopt’

‘no-powerpc-gpopt’

Generate code that uses (does not use) the optional PowerPC architecture instructions in the General Purpose group, including floating-point square root.

‘recip-precision’

‘no-recip-precision’

Assume (do not assume) that the reciprocal estimate instructions provide higher-precision estimates than is mandated by the PowerPC ABI.

‘string’

‘no-string’

Generate code that uses (does not use) the load string instructions and the store string word instructions to save multiple registers and do small block moves.

‘vsx’

‘no-vsx’

Generate code that uses (does not use) vector/scalar (VSX) instructions, and also enable the use of built-in functions that allow more direct access to the VSX instruction set. In 32-bit code, you cannot enable VSX or AltiVec instructions unless -mabi=altivec is used on the command line.

‘friz’

‘no-friz’

Generate (do not generate) the friz instruction when the -funsafe-math-optimizations option is used to optimize rounding a floating-point value to 64-bit integer and back to floating point. The friz instruction does not return the same value if the floating-point number is too large to fit in an integer.

‘avoid-indexed-addresses’

‘no-avoid-indexed-addresses’

Generate code that tries to avoid (not avoid) the use of indexed load or store instructions.

‘paired’

‘no-paired’

Generate code that uses (does not use) the generation of PAIRED simd instructions.

‘longcall’

‘no-longcall’

Generate code that assumes (does not assume) that all calls are far away so that a longer more expensive calling sequence is required.

‘cpu=CPU’

Specify the architecture to generate code for when compiling the function. If you select the target("cpu=power7") attribute when generating 32-bit code, VSX and AltiVec instructions are not generated unless you use the -mabi=altivec option on the command line.

‘tune=TUNE’

Specify the architecture to tune for when compiling the function. If you do not specify the target("tune=TUNE") attribute and you do specify the target("cpu=CPU") attribute, compilation tunes for the CPU architecture, and not the default tuning specified on the command line.

On the PowerPC, the inliner does not inline a function that has different target options than the caller, unless the callee has a subset of the target options of the caller.