https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124838
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |pinskia at gcc dot gnu.org
Resolution|WONTFIX |---
Keywords| |missed-optimization
Status|RESOLVED |NEW
Last reconfirmed| |2026-04-10
Ever confirmed|0 |1
--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
int bar3(unsigned long x) { return x ? __builtin_clzl(x) : 64; }
works, the pattern detection is confused by the conversion to unsinged long
which moved inside the conditional early:
return x != 0 ? (long unsigned int) __builtin_clzl (x) : 64;
without that phiopt1 could
phiopt match-simplify trying:
x_2(D) != 0 ? _4 : 64
Applying pattern match.pd:10864, gimple-match-9.cc:6415
phiopt match-simplify back:
_3 = .CLZ (x_2(D), 64);
result: _3
rejected because early
but phiopt2 then performs the transform. Not with the conversion though
as we match
(for func (CLZ)
(simplify
(cond (ne @0 integer_zerop@1) (func (convert?@3 @0)) INTEGER_CST@2)
I think we want to fix both, not reject early and add another
convert? around func and adjust phiopt to then consider the folding,
which it does not.
