[Bug middle-end/107443] [10/11/12/13 Regression] Removing switch with __builtin_unreachable causes missed optimizations
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107443 Richard Biener changed: What|Removed |Added Priority|P3 |P2
[Bug middle-end/107443] [10/11/12/13 Regression] Removing switch with __builtin_unreachable causes missed optimizations
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107443 Richard Biener changed: What|Removed |Added CC||marxin at gcc dot gnu.org, ||rguenth at gcc dot gnu.org --- Comment #2 from Richard Biener --- I think we simply "optimize" the switch instead of, like for the if, preserving the range asserting side-effect until some point in the compilation. Ideally switch conversion would turn the switch side-effect into a single if. But I also think the testcase is somewhat artificial so I wonder if we should worry here at all ...
[Bug middle-end/107443] [10/11/12/13 Regression] Removing switch with __builtin_unreachable causes missed optimizations
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107443
Andrew Pinski changed:
What|Removed |Added
Target Milestone|--- |10.5
Last reconfirmed||2022-10-27
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Known to fail||8.1.0
Summary|Switch conversion removing |[10/11/12/13 Regression]
|code|Removing switch with
||__builtin_unreachable
||causes missed optimizations
Known to work||7.1.0
--- Comment #1 from Andrew Pinski ---
Testcase which shows this is a regression and switch conversion just exposed
it:
void dead (unsigned n);
void foo (unsigned n);
void func (unsigned n)
{
switch(n) {
case 0:
__builtin_unreachable();
case 1:
__builtin_unreachable();
case 2:
__builtin_unreachable();
case 3:
__builtin_unreachable();
case 4:
__builtin_unreachable();
case 5:
__builtin_unreachable();
case 6:
__builtin_unreachable();
case 7:
__builtin_unreachable();
default:
;
}
foo (n);
if (n < 8)
dead (n);
}
after building the CFG we get with the above testcase:
Removing basic block 10
Removing basic block 9
Removing basic block 8
Removing basic block 7
Removing basic block 6
Removing basic block 5
Removing basic block 4
Removing basic block 3
Merging blocks 2 and 11
