[PATCH] AArch64 compile dbl-64/e_sqrt.c with -ffp-contract=off

[PATCH] AArch64 compile dbl-64/e_sqrt.c with -ffp-contract=off

[Marcus Shawcroft]

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This patch fixes the numerical errors in aarch64 sqrt() due to the
compilers use of fnmsub (negated fused multiply-subtract).

Previous thread:
https://sourceware.org/ml/libc-alpha/2013-12/msg00473.html

I'll leave this on the list for 24 hours before committing to give
folks the opportunity to comment on the (in)appropriateness of my
solution...

Cheers
/Marcus

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diff --git a/ports/ChangeLog.aarch64 b/ports/ChangeLog.aarch64
index 09645c3..e65e87a 100644
--- a/ports/ChangeLog.aarch64
+++ b/ports/ChangeLog.aarch64
@@ -1,3 +1,8 @@
+2013-12-17  Marcus Shawcroft  <marcus.shawcroft@linaro.org>
+
+	* sysdeps/aarch64/Makefile (CFLAGS-e_sqrt.c): Add
+	$(config-cflags-nofma).
+
 2013-12-17  Marcus Shawcroft  <marcus.shawcroft@linaro.org>
 
 	* sysdeps/aarch64/libm-test-ulps: Regenerated.
diff --git a/ports/sysdeps/aarch64/Makefile b/ports/sysdeps/aarch64/Makefile
index 5af7a16..43341c1 100644
--- a/ports/sysdeps/aarch64/Makefile
+++ b/ports/sysdeps/aarch64/Makefile
@@ -14,3 +14,7 @@ endif
 ifeq ($(subdir),csu)
 gen-as-const-headers += tlsdesc.sym
 endif
+
+ifeq ($(subdir),math)
+CFLAGS-e_sqrt.c = $(config-cflags-nofma)
+endif

Re: [PATCH] AArch64 compile dbl-64/e_sqrt.c with -ffp-contract=off

[Joseph S. Myers]

On Tue, 17 Dec 2013, Marcus Shawcroft wrote:

> This patch fixes the numerical errors in aarch64 sqrt() due to the
> compilers use of fnmsub (negated fused multiply-subtract).
> 
> Previous thread:
> https://sourceware.org/ml/libc-alpha/2013-12/msg00473.html
> 
> I'll leave this on the list for 24 hours before committing to give
> folks the opportunity to comment on the (in)appropriateness of my
> solution...

The source file in question is architecture-independent, so the makefile 
change should also be architecture-independent (i.e. in 
sysdeps/ieee754/dbl-64/Makefile).

-- 
Joseph S. Myers
joseph@codesourcery.com