On November 6, 2015 3:34:22 PM GMT+01:00, Richard Sandiford
<richard.sandif...@arm.com> wrote:
>At the moment the ECF_* flags for a gimple call to a built-in
>function are derived from the function decl, which in turn is
>derived from the global command-line options. So if the compiler
>is run with -fno-math-errno, we always assume functions don't set
>errno, regardless of local optimization options. Similarly if the
>compiler is run with -fmath-errno, we always assume functions set
>errno.
>
>This shows up in gcc.dg/lto/20110201-1_0.c, where we compile
>the file with -O0 and use -O2 -ffast-math for a specific function.
>-O2 -ffast-math is enough for us to convert cabs to sqrt as hoped,
>but because of the global -fmath-errno setting, we assume that the
>call to sqrt is not pure or const and create vops for it. This makes
>it appear to the gimple code that a simple sqrt optab isn't enough.
>
>Later patches move more decisions about maths functions to gimple
>and think that in this case we should use:
>
> y = sqrt (x);
> if (!(x >= 0))
> sqrt (x); // to set errno.
>
>This is being tracked as PR68235. For now the patch adds
>-fno-math-errno to the dg-options for this test.
>
>Tested on x86_64-linux-gnu, aarch64-linux-gnu and arm-linux-gnueabi.
>OK to install?
OK.
>Thanks,
>Richard
>
>gcc/testsuite/
> PR tree-optimization/68235
> * gcc.dg/lto/20110201-1_0.c: Add -fno-math-errno.
>
>diff --git a/gcc/testsuite/gcc.dg/lto/20110201-1_0.c
>b/gcc/testsuite/gcc.dg/lto/20110201-1_0.c
>index 068dddc..2144f07 100644
>--- a/gcc/testsuite/gcc.dg/lto/20110201-1_0.c
>+++ b/gcc/testsuite/gcc.dg/lto/20110201-1_0.c
>@@ -1,6 +1,6 @@
> /* { dg-lto-do run } */
>-/* { dg-lto-options { { -O0 -flto } } } */
>-/* { dg-lto-options { "-O0 -flto -mfloat-abi=softfp -mfpu=neon-vfpv4"
>} { target arm*-*-* } } */
>+/* { dg-lto-options { { -O0 -flto -fno-math-errno } } } */
>+/* { dg-lto-options { "-O0 -flto -fno-math-errno -mfloat-abi=softfp
>-mfpu=neon-vfpv4" } { target arm*-*-* } } */
> /* { dg-require-linker-plugin "" } */
> /* { dg-require-effective-target sqrt_insn } */
>
