https://bugs.llvm.org/show_bug.cgi?id=45688
Bug ID: 45688
Summary: Missed optimization on comparison after knowing
__builtin_uadd_overflow didn't overflow
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
bool f(unsigned a, unsigned b)
{
unsigned result;
bool overflowed = __builtin_uadd_overflow(a, b, &result);
__builtin_assume(!overflowed);
return result >= b;
}
This can be optimized to `return 1;`. This transformation is done by GCC, but
not by LLVM.
Comparison here : https://godbolt.org/z/i44m2a
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