Enable UNALIGNED_ACCESS_IS_FAST for all PowerPC variants#448
Merged
ebiggers merged 1 commit intoebiggers:masterfrom Mar 16, 2026
Merged
Enable UNALIGNED_ACCESS_IS_FAST for all PowerPC variants#448ebiggers merged 1 commit intoebiggers:masterfrom
ebiggers merged 1 commit intoebiggers:masterfrom
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The existing check only tests __powerpc64__, which is defined on 64-bit Linux/BSD PowerPC. Add __powerpc__ (32-bit Linux/BSD) and __POWERPC__ (Darwin/macOS, both 32-bit and 64-bit ABI) so that all PowerPC platforms benefit from the fast unaligned access code paths. All PowerPC processors support unaligned 32-bit integer access in hardware with minimal penalty, so the byte-by-byte fallback path is unnecessarily conservative on these platforms. Tested on Power Mac G5 (Darwin 9.8.0, GCC 10.5.0) where only __POWERPC__ is defined — the fix correctly enables the fast path. Also verified on IBM POWER8 S824 (ppc64le, GCC 9.4.0). Fixes ebiggers#362
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Merged, thanks. |
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Problem
The
UNALIGNED_ACCESS_IS_FASTcheck incommon_defs.honly tests__powerpc64__, which misses:__powerpc__instead__POWERPC__insteadThis causes all Mac PowerPC builds (G3/G4/G5) and 32-bit Linux PowerPC
to take the slow byte-by-byte code path unnecessarily.
Fixes #362
Fix
Add
__powerpc__and__POWERPC__to the preprocessor conditional alongside the existing__powerpc64__check.Testing
Power Mac G5 (Darwin 9.8.0, GCC 10.5.0, big-endian PPC):
__POWERPC__is defined (not__powerpc64__or__powerpc__)UNALIGNED_ACCESS_IS_FAST = 0(missed)UNALIGNED_ACCESS_IS_FAST = 1(detected)IBM POWER8 S824 (Ubuntu 20.04, GCC 9.4.0, ppc64le):
__powerpc64__and__powerpc__defined__powerpc64__, still works with the additional checksMacro coverage
__powerpc64____powerpc____POWERPC__