https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93447
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Severity|normal |enhancement
Last reconfirmed| |2021-12-17
Status|UNCONFIRMED |NEW
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
Here is a simple testcase which shows the issue even
/* { dg-do compile } */
/* { dg-options "-Os -fdump-tree-optimized" } */
_Bool g(int, int, int *a);
_Bool addb_simple(int A, int B, int *Rp)
{
int ec=0;
if(g(A,B,Rp))
ec = -777;
return !!ec;
}
/* The call to g should be tail called. */
/* { dg-final { scan-tree-dump-times "tail call" 1 "optimized"} } */
PRE for -Os does not do partial redundancy elimination, only code hoisting and
fully redundancy elimination which is why it is not doing it for -Os. What PRE
does not notice is d_5 is not being used so it is fully redundant but I don't
know if PRE/FRE is the right place for this.
