[PATCH v2] math: Fix x86_64 build for -Os (BZ 33367)
Adhemerval Zanella
adhemerval.zanella@linaro.org
Mon Sep 8 19:55:31 GMT 2025
The compiler might not inline the trunc function call for
USE_TRUNC_BUILTIN [1].
This patch adds an optimized __trunc/__truncf for x86 used
on modf ifunc variant to avoid the trunc libcall.
Checked on x86_64, x86_64-v2, x86_64-v3, and x86_64-v4. Used -O2 and
-Os options. Performed a full make check on x86_64 with both
optimizations.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121861
---
sysdeps/x86/fpu/math_private.h | 27 +++++++++++++++++++
sysdeps/x86_64/fpu/multiarch/s_modf-avx.c | 4 +++
sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c | 4 +++
sysdeps/x86_64/fpu/multiarch/s_modf.c | 3 ++-
sysdeps/x86_64/fpu/multiarch/s_modff-avx.c | 4 +++
sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c | 4 +++
sysdeps/x86_64/fpu/multiarch/s_modff.c | 3 ++-
7 files changed, 47 insertions(+), 2 deletions(-)
diff --git a/sysdeps/x86/fpu/math_private.h b/sysdeps/x86/fpu/math_private.h
index 132f011809..d30d580cea 100644
--- a/sysdeps/x86/fpu/math_private.h
+++ b/sysdeps/x86/fpu/math_private.h
@@ -19,6 +19,7 @@
#ifndef X86_MATH_PRIVATE_H
#define X86_MATH_PRIVATE_H 1
+#include <math.h>
#include_next <math_private.h>
__extern_always_inline long double
@@ -29,4 +30,30 @@ __NTH (__ieee754_atan2l (long double y, long double x))
return ret;
}
+__extern_always_inline double
+__trunc (double x)
+{
+#ifdef __AVX__
+ asm ("vroundsd $11, %1, %1, %0" : "=v" (x) : "v" (x));
+#elif defined __SSE4_1__
+ asm ("roundsd $11, %1, %0" : "=x" (x) : "x" (x));
+#else
+ x = trunc (x);
+#endif
+ return x;
+}
+
+__extern_always_inline float
+__truncf (float x)
+{
+#ifdef __AVX__
+ asm ("vroundss $11, %1, %1, %0" : "=v" (x) : "v" (x));
+#elif defined __SSE4_1__
+ asm ("roundss $11, %1, %0" : "=x" (x) : "x" (x));
+#else
+ x = truncf (x);
+#endif
+ return x;
+}
+
#endif
diff --git a/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c b/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c
index ab4f03db0e..2f84d254a9 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_modf-avx.c
@@ -1,3 +1,7 @@
+#include <sysdeps/x86/isa-level.h>
+#include <math_private.h>
+
#define __modf __modf_avx
+#define trunc __trunc
#include <sysdeps/ieee754/dbl-64/s_modf.c>
diff --git a/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c b/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c
index 00aa8cd736..dcf04097f2 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_modf-sse4_1.c
@@ -1,3 +1,7 @@
+#include <sysdeps/x86/isa-level.h>
+#include <math_private.h>
+
#define __modf __modf_sse41
+#define trunc __trunc
#include <sysdeps/ieee754/dbl-64/s_modf.c>
diff --git a/sysdeps/x86_64/fpu/multiarch/s_modf.c b/sysdeps/x86_64/fpu/multiarch/s_modf.c
index e365bfcef7..61f77566b1 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_modf.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_modf.c
@@ -18,7 +18,6 @@
#include <sysdeps/x86/isa-level.h>
#if MINIMUM_X86_ISA_LEVEL < AVX_X86_ISA_LEVEL
-# define NO_MATH_REDIRECT
# include <libm-alias-double.h>
# define modf __redirect_modf
@@ -38,4 +37,6 @@ libm_alias_double (__modf, modf)
# define __modf __modf_sse2
# endif
#endif
+#include <math_private.h>
+#define trunc __trunc
#include <sysdeps/ieee754/dbl-64/s_modf.c>
diff --git a/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c b/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c
index 07cb9c1036..c121ec26e2 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_modff-avx.c
@@ -1,3 +1,7 @@
+#include <sysdeps/x86/isa-level.h>
+#include <math_private.h>
+
#define __modff __modff_avx
+#define truncf __truncf
#include <sysdeps/ieee754/flt-32/s_modff.c>
diff --git a/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c b/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c
index 060c5e3979..30a785d385 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_modff-sse4_1.c
@@ -1,3 +1,7 @@
+#include <sysdeps/x86/isa-level.h>
+#include <math_private.h>
+
#define __modff __modff_sse41
+#define truncf __truncf
#include <sysdeps/ieee754/flt-32/s_modff.c>
diff --git a/sysdeps/x86_64/fpu/multiarch/s_modff.c b/sysdeps/x86_64/fpu/multiarch/s_modff.c
index a4b5429037..ebf16777fd 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_modff.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_modff.c
@@ -18,7 +18,6 @@
#include <sysdeps/x86/isa-level.h>
#if MINIMUM_X86_ISA_LEVEL < AVX_X86_ISA_LEVEL
-# define NO_MATH_REDIRECT
# include <libm-alias-float.h>
# define modff __redirect_modff
@@ -38,4 +37,6 @@ libm_alias_float (__modf, modf)
# define __modff __modff_sse2
# endif
#endif
+#include <math_private.h>
+#define truncf __truncf
#include <sysdeps/ieee754/flt-32/s_modff.c>
--
2.43.0
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