https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64225
--- Comment #5 from jgreenhalgh at gcc dot gnu.org ---
I've seen similar behavior on an HPC benchmark I was looking at.
The problem here is the interaction between fold-const.c, other passes, and
-fmath-errno.
Take this testcase:
void
foo (double x)
{
x * x;
}
fold-const.c is going to see x *x and canonicalize it to a call to pow. No
other pass will want to touch it, because now it could set errno, so we get as
code generation:
foo:
fmov d1, 2.0e+0
b pow
If we add -fno-math-errno :
foo:
ret
When I looked at this before I convinced myself that fold-const.c shouldn't be
doing the canonicalization to pow if we cared about errno - but I never spun a
patch for it - and I'm not sure I'm right.
