2b78303e3f
Just like for regular IR we need to treat SELECT as conditionally blocking poison in SelectionDAG. So (unless the condition itself is poison) the result is only poison if the selected true/false value is poison. Thus, when doing DAG combines that turn SELECT into arithmetic/logical operations (e.g. AND/OR) we need to make sure that the new operations aren't more poisonous. One way to do that is to use FREEZE to make sure the operands aren't posion. This patch aims at fixing the kind of miscompiles reported in https://github.com/llvm/llvm-project/issues/84653 and https://github.com/llvm/llvm-project/issues/85190 Solution is to make sure that we insert FREEZE, if needed to make the fold sound, when using the foldBoolSelectToLogic and foldVSelectToSignBitSplatMask DAG combines.
26 lines
859 B
LLVM
26 lines
859 B
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
|
|
; RUN: llc -mtriple=x86_64-- < %s | FileCheck %s
|
|
|
|
; It's not possible to directly or the two loads together, because this might
|
|
; propagate a poison value from the second load (which has !range but not
|
|
; !noundef).
|
|
define i8 @test(ptr %p) {
|
|
; CHECK-LABEL: test:
|
|
; CHECK: # %bb.0:
|
|
; CHECK-NEXT: movzbl 1(%rdi), %eax
|
|
; CHECK-NEXT: orb (%rdi), %al
|
|
; CHECK-NEXT: setne %al
|
|
; CHECK-NEXT: addb %al, %al
|
|
; CHECK-NEXT: retq
|
|
%v1 = load i8, ptr %p, align 4, !range !0, !noundef !{}
|
|
%cmp1 = icmp ne i8 %v1, 0
|
|
%p2 = getelementptr inbounds i8, ptr %p, i64 1
|
|
%v2 = load i8, ptr %p2, align 1, !range !0
|
|
%cmp2 = icmp ne i8 %v2, 0
|
|
%or = select i1 %cmp1, i1 true, i1 %cmp2
|
|
%res = select i1 %or, i8 2, i8 0
|
|
ret i8 %res
|
|
}
|
|
|
|
!0 = !{i8 0, i8 2}
|