diff options
| author |  Derek Mauro <dmauro@google.com> | 2024-05-03 09:14:22 -0700 |
|---|---|---|
| committer |  Copybara-Service <copybara-worker@google.com> | 2024-05-03 09:15:27 -0700 |
| commit | c1e1b47d989978cde8c5a2a219df425b785a0c47 (patch) | |
| tree | 7e346e387f88420cff4da113e1a1d9ac23223ed3 | |
| parent | 7e149e40c7a2d8049ecd28d1f83f64cc197cc128 (diff) | |
Use __builtin_ctzg and __builtin_clzg in the implementations of
CountTrailingZeroesNonzero16 and CountLeadingZeroes16 when they are
available.
GCC 14 and Clang 19 adds these new builtins. The g-suffix is for
"generic". The s-suffix on __builtin_ctzs and __builtin_clzs is for
"short". GCC never implemented the short versions and #1664 reports
GCC 14 (pre-release) gives an error here, although this may be a
pre-release bug.
Fixes #1664
PiperOrigin-RevId: 630408249
Change-Id: I4aedcc82b85430f50d025f8eb1cab089c6fcd1bc
| -rw-r--r-- | absl/numeric/internal/bits.h | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/absl/numeric/internal/bits.h b/absl/numeric/internal/bits.h index bfef06bc..0917464d 100644 --- a/absl/numeric/internal/bits.h +++ b/absl/numeric/internal/bits.h @@ -167,7 +167,9 @@ CountLeadingZeroes32(uint32_t x) { ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_CLZ inline int CountLeadingZeroes16(uint16_t x) { -#if ABSL_HAVE_BUILTIN(__builtin_clzs) +#if ABSL_HAVE_BUILTIN(__builtin_clzg) + return x == 0 ? 16 : __builtin_clzg(x); +#elif ABSL_HAVE_BUILTIN(__builtin_clzs) static_assert(sizeof(unsigned short) == sizeof(x), // NOLINT(runtime/int) "__builtin_clzs does not take 16-bit arg"); return x == 0 ? 16 : __builtin_clzs(x); @@ -303,7 +305,9 @@ CountTrailingZeroesNonzero64(uint64_t x) { ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_CTZ inline int CountTrailingZeroesNonzero16(uint16_t x) { -#if ABSL_HAVE_BUILTIN(__builtin_ctzs) +#if ABSL_HAVE_BUILTIN(__builtin_ctzg) + return __builtin_ctzg(x); +#elif ABSL_HAVE_BUILTIN(__builtin_ctzs) static_assert(sizeof(unsigned short) == sizeof(x), // NOLINT(runtime/int) "__builtin_ctzs does not take 16-bit arg"); return __builtin_ctzs(x); |