6e518a3b50
This regresses a test in LoopVectorize, so I'll need to go away and think about how to solve this in a way that isn't broken. From the writeup in PR26071: What's happening is that ComputeKnownZeroes is telling us that all bits except the LSB are zero. We're then deciding that only the LSB needs to be demanded from the icmp's inputs. This is where we're wrong - we're assuming that after simplification the bits that were known zero will continue to be known zero. But they're not - during trivialization the upper bits get changed (because an XOR isn't shrunk), so the icmp fails. The fault is in demandedbits - its contract does clearly state that a non-demanded bit may either be zero or one. llvm-svn: 259649
13 lines
399 B
LLVM
13 lines
399 B
LLVM
; RUN: opt -S -demanded-bits -analyze < %s | FileCheck %s
|
|
|
|
; CHECK-LABEL: 'test_mul'
|
|
; CHECK-DAG: DemandedBits: 0xFF for %1 = add nsw i32 %a, 5
|
|
; CHECK-DAG: DemandedBits: 0xFF for %3 = trunc i32 %2 to i8
|
|
; CHECK-DAG: DemandedBits: 0xFF for %2 = mul nsw i32 %1, %b
|
|
define i8 @test_mul(i32 %a, i32 %b) {
|
|
%1 = add nsw i32 %a, 5
|
|
%2 = mul nsw i32 %1, %b
|
|
%3 = trunc i32 %2 to i8
|
|
ret i8 %3
|
|
}
|