https://bugs.llvm.org/show_bug.cgi?id=46472
Bug ID: 46472
Summary: Optimize some bit magic into a faster pattern when
nand is not available
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: gabrav...@gmail.com
CC: llvm-bugs@lists.llvm.org
int f(int a, int b, int c)
{
return (a & ~c) | (b & c);
}
Unless the target architecture has a nand intruction available (such as x86
with BMI) this can be optimized to `return ((b ^ a) & c) ^ a;`. This
transformation is done by GCC (though sadly it also does it when nand is
available), but not by LLVM
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