https://bugs.llvm.org/show_bug.cgi?id=45686
Bug ID: 45686
Summary: Failure to combine assumptions on range of value of
variable
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
void foo(int a, int b, bool c)
{
__builtin_assume(a < 234);
__builtin_assume(b > 789);
int d = (c ? a : b);
if (d >= 234 && d <= 789)
g();
}
GCC optimizes the entire function out, LLVM does not. Most likely we'd want
LLVM to combine the assumptions on `a` and `b` in such a way that `d >= 234 &&
d <= 789` would be considered always false afterwards
Comparison here : https://godbolt.org/z/f4uWiY
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