On one machine I see gcc.dg/tree-ssa/pr71078-3.c FAILing with -m32 because libc provides
extern __inline __attribute__ ((__always_inline__)) __attribute__ ((__gnu_inline__)) double __attribute__ ((__nothrow__ , __leaf__)) fabs (double __x) { return __builtin_fabs (__x); } which makes CSE necessary to catch the pattern (see PR79333). The following adjusts the testcase to not rely on math.h. Tested on x86_64-unknown-linux-gnu, applied. Richard. 2017-02-02 Richard Biener <rguent...@suse.de> * gcc.dg/tree-ssa/pr71078-3.c: Do not rely on math.h. Index: gcc/testsuite/gcc.dg/tree-ssa/pr71078-3.c =================================================================== --- gcc/testsuite/gcc.dg/tree-ssa/pr71078-3.c (revision 245090) +++ gcc/testsuite/gcc.dg/tree-ssa/pr71078-3.c (working copy) @@ -1,9 +1,10 @@ /* { dg-do compile } */ /* { dg-require-effective-target large_double } */ /* { dg-require-effective-target c99_runtime } */ -/* { dg-options "-O2 -ffast-math -fdump-tree-forwprop-details" } */ +/* { dg-options "-O2 -ffast-math -fdump-tree-forwprop1-details" } */ + +extern double fabs (double); -#include <math.h> double f(float f) { double t1 = fabs(f);