[InstCombine] fix miscompile from umul_with_overflow matching
As noted in PR46561:
https://bugs.llvm.org/show_bug.cgi?id=46561
...it takes something beyond a minimal IR example to trigger
this bug because it relies on matching non-canonical IR.
There are no tests that show the need for matching this
pattern, so I'm just deleting it to fix the miscompile.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 31cd8e4..f1233b6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4646,17 +4646,6 @@
case ICmpInst::ICMP_NE:
// Recognize pattern:
// mulval = mul(zext A, zext B)
- // cmp eq/neq mulval, zext trunc mulval
- if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
- if (Zext->hasOneUse()) {
- Value *ZextArg = Zext->getOperand(0);
- if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
- if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
- break; //Recognized
- }
-
- // Recognize pattern:
- // mulval = mul(zext A, zext B)
// cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
ConstantInt *CI;
Value *ValToMask;
diff --git a/llvm/test/Transforms/InstCombine/icmp-mul-zext.ll b/llvm/test/Transforms/InstCombine/icmp-mul-zext.ll
index 31540e6..9b4d994 100644
--- a/llvm/test/Transforms/InstCombine/icmp-mul-zext.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-mul-zext.ll
@@ -121,16 +121,20 @@
ret i16 %trunc_unnecessary ; crash visiting this use after corrupting iterator
}
-; FIXME: This miscompiles because of broken pattern matching.
+; This miscompiled because of broken pattern matching.
define i1 @PR46561(i1 %a, i1 %x, i1 %y, i8 %z) {
; CHECK-LABEL: @PR46561(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[A:%.*]], label [[COND_TRUE:%.*]], label [[END:%.*]]
; CHECK: cond.true:
+; CHECK-NEXT: [[MULBOOL:%.*]] = and i1 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[Z:%.*]], 1
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: [[PHI_CMP:%.*]] = xor i1 [[TMP1]], [[MULBOOL]]
; CHECK-NEXT: br label [[END]]
; CHECK: end:
-; CHECK-NEXT: [[P:%.*]] = phi i1 [ true, [[COND_TRUE]] ], [ false, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[P:%.*]] = phi i1 [ [[PHI_CMP]], [[COND_TRUE]] ], [ false, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i1 [[P]]
;
entry:
