https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111541
Bug ID: 111541
Summary: missing optimization x & ~c | (y | c) -> x | (y | c)
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: vanyacpp at gmail dot com
Target Milestone: ---
On this function clang generates shorter code:
unsigned foo(unsigned x, unsigned y, unsigned c)
{
return x & ~c | (y | c);
}
Clang notices that the expression can be simplified to x | (y | c). It would be
great if GCC can do the same.
https://gcc.godbolt.org/z/dMo4nEjrs
This issue is symmetric to the one described in PR 98710. The idea behind this
simplification is the following: when we are working with bitsets, "|" can be
read as adding bits and "&~" as removing. Therefore the expression "x & ~c | (y
| c)" can be read as removing "c" from "x" and then adding "y | c".
So the simplification
x & ~c | (y | c) -> x | (y | c)
means there is no need to remove "c" if later we add something containing "c".
