https://bugs.llvm.org/show_bug.cgi?id=48408
Bug ID: 48408
Summary: Failure to optimize out comparison when very narrow
range is already known
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
#ifndef __clang__
__attribute__((always_inline)) inline void __builtin_assume(bool condition)
{
if (!condition)
__builtin_unreachable();
}
#endif
bool f(int a)
{
__builtin_assume((a == -1) || (a == 0));
return a < -1;
}
This can be optimized to `return false;`. This transformation is done by GCC,
but not by LLVM.
See also Godbolt comparison here : https://godbolt.org/z/8x5x89
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