https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96226
Bug ID: 96226
Summary: Failure to optimize shift+not to rotate
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
int32_t f(int32_t x)
{
return ~(1 << (x & 0x1F));
}
This can be transformed to doing a rotate of -2 and x. This transformation is
done by LLVM, but not by GCC.
PS: GCC seems capable of doing this optimization, but only if `x & 0x1F` is
replaced with `x`, which either means that GCC is underoptimizing this or that
LLVM is somehow wrong.
