[llvm-bugs] [Bug 48406] New: Failure to optimize out abs when sign is known
via llvm-bugs
llvm-bugs at lists.llvm.org
Sat Dec 5 19:06:47 PST 2020
https://bugs.llvm.org/show_bug.cgi?id=48406
Bug ID: 48406
Summary: Failure to optimize out abs when sign is known
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedbugs at nondot.org
Reporter: gabravier at gmail.com
CC: llvm-bugs at lists.llvm.org
int f(int x)
{
__builtin_assume(x <= 0);
return abs(x);
}
This can be optimized to `return -x;`. This transformation is done by GCC (with
__builtin_assume replaced by `if (!(x <= 0)) __builtin_unreachable()`), but not
by LLVM.
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