https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85390
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to fail| |7.1.0
Last reconfirmed| |2021-12-16
Target Milestone|--- |9.5
Keywords| |needs-bisection
Ever confirmed|0 |1
Summary|possible missed |[9/10/11/12 Regression]
|optimisation / regression |possible missed
|from 6.3 with conditional |optimisation / regression
|expression |from 6.3 with conditional
| |expression
CC| |pinskia at gcc dot gnu.org
Status|UNCONFIRMED |NEW
Component|rtl-optimization |tree-optimization
Known to work| |6.4.0
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Ok, the issue is just dumb luck:
Take:
extern int a, b, c;
int f(int x)
{
__builtin_prefetch((void *) (__SIZE_TYPE__)(x ? a : b));
return c;
}
int f1(int x)
{
int t = x ? a :b;
__builtin_prefetch((void *)(__SIZE_TYPE__)t);
return c;
}
The f1 uses cmov while f does not.
The gimple level difference is there is two cast (one in each branch) for f
while only one cast outside of the PHI node.
But that was that way even in GCC 6.
I wonder what changed in GCC 7 which caused this issue to appear.
