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Bug: https://bugs.gentoo.org/934337
From: https://github.com/abseil/abseil-cpp/commit/c1e1b47d989978cde8c5a2a219df425b785a0c47.patch
From c1e1b47d989978cde8c5a2a219df425b785a0c47 Mon Sep 17 00:00:00 2001
From: Derek Mauro <dmauro@google.com>
Date: Fri, 3 May 2024 09:14:22 -0700
Subject: [PATCH] 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
---
absl/numeric/internal/bits.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/absl/numeric/internal/bits.h b/absl/numeric/internal/bits.h
index bfef06bce1f..0917464d6ad 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);
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