aarch64: Fix f{max,min}{f} build for GCC 4.9 and 5

Message ID 1510914762-27547-1-git-send-email-adhemerval.zanella@linaro.org
State New
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Series
  • aarch64: Fix f{max,min}{f} build for GCC 4.9 and 5
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Commit Message

Adhemerval Zanella Nov. 17, 2017, 10:32 a.m.
GCC 4.9 and 5 do not generate a correct f{max,min}nm instruction for
__builtin_{fmax,fmin}{f} without -ffinite-math-only.  It is clear a
compiler issue since the instruction can handle NaN and Inf correctly
and GCC6+ does not show this issue.

We backport a fix to GCC 5, raise the minimum required GCC version
for aarch64 (since GCC 4.9 branch is now closed) and/or add configure
check to check for this issue.  However I think -ffinit-math-only
should be safe for these specific implementation and it is a much
simpler solution.

Checked on aarch64-linux-gnu with GCC 5.3.1.

	* sysdeps/aarch64/fpu/Makefile (CFLAGS-s_fmax.c, CFLAGS-s_fmaxf.c,
	CFLAGS-s_fmin.c, CFLAGS-s_fminf.c): New rule: add -ffinite-math-only.

[1] https://gcc.gnu.org/ml/gcc/2016-08/msg00010.html

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

---
 ChangeLog                    | 5 +++++
 sysdeps/aarch64/fpu/Makefile | 6 ++++++
 2 files changed, 11 insertions(+)

-- 
2.7.4

Comments

Szabolcs Nagy Nov. 17, 2017, 10:40 a.m. | #1
On 17/11/17 10:32, Adhemerval Zanella wrote:
> GCC 4.9 and 5 do not generate a correct f{max,min}nm instruction for

> __builtin_{fmax,fmin}{f} without -ffinite-math-only.  It is clear a

> compiler issue since the instruction can handle NaN and Inf correctly

> and GCC6+ does not show this issue.

> 

> We backport a fix to GCC 5, raise the minimum required GCC version

> for aarch64 (since GCC 4.9 branch is now closed) and/or add configure

> check to check for this issue.  However I think -ffinit-math-only

> should be safe for these specific implementation and it is a much

> simpler solution.

> 

> Checked on aarch64-linux-gnu with GCC 5.3.1.

> 

> 	* sysdeps/aarch64/fpu/Makefile (CFLAGS-s_fmax.c, CFLAGS-s_fmaxf.c,

> 	CFLAGS-s_fmin.c, CFLAGS-s_fminf.c): New rule: add -ffinite-math-only.

> 


OK.

Patch

diff --git a/sysdeps/aarch64/fpu/Makefile b/sysdeps/aarch64/fpu/Makefile
index bf38f2c..4a182bd 100644
--- a/sysdeps/aarch64/fpu/Makefile
+++ b/sysdeps/aarch64/fpu/Makefile
@@ -5,4 +5,10 @@  CFLAGS-s_lroundf.c += -fno-math-errno
 CFLAGS-s_lround.c += -fno-math-errno
 CFLAGS-s_llroundf.c += -fno-math-errno
 CFLAGS-s_llround.c += -fno-math-errno
+# GCC 4.9 and 5 requires the flag to correct emits a f{max,min}nm
+# for a __builtin_{fmax,fmin}{f}.
+CFLAGS-s_fmax.c += -ffinite-math-only
+CFLAGS-s_fmaxf.c += -ffinite-math-only
+CFLAGS-s_fmin.c += -ffinite-math-only
+CFLAGS-s_fminf.c += -ffinite-math-only
 endif