I've been doing some benchmarking of gfortran, and reducing the
testcase leads to what seems a missed optimization in the following
code:
$ cat a.c
void foo (float * restrict x, float * restrict y)
{
int i;
for (i = 0; i < 10000; i++)
x[i] = y[i] * y[i];
}
$ gcc a.c -O1 -ffast-math -msse -mfpmath=sse -ftree-vectorize
-ftree-vectorizer-verbose=5 -std=c99 -c
a.c:5: note: Alignment of access forced using peeling.
a.c:5: note: Vectorizing an unaligned access.
a.c:5: note: not vectorized: relevant stmt not supported: D.1353_14 =
__builtin_powf (D.1352_13, 2.0e+0)
a.c:5: note: vectorized 0 loops in function.
I find in fold-const.c:fold_binary, around line 9091, I found the following:
/* Optimize x*x as pow(x,2.0), which is expanded as x*x. */
Should I file it as a missed-optimization bug in bugzilla, or is there
some clever reason for that behaviour?
FX
