[llvm] [CVP] Flip signedness icmp predicate in use level (PR #69948)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: XChy (XChy)

<details>
<summary>Changes</summary>

Resolve #<!-- -->69928.
[Alive2 Proof](https://alive2.llvm.org/ce/z/zoqaqf).


---
Full diff: https://github.com/llvm/llvm-project/pull/69948.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp (+3-2) 
- (modified) llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll (+75) 


``````````diff
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 523196e5e6eab71..9043c434313fedc 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -294,8 +294,9 @@ static bool processICmp(ICmpInst *Cmp, LazyValueInfo *LVI) {
 
   ICmpInst::Predicate UnsignedPred =
       ConstantRange::getEquivalentPredWithFlippedSignedness(
-          Cmp->getPredicate(), LVI->getConstantRange(Cmp->getOperand(0), Cmp),
-          LVI->getConstantRange(Cmp->getOperand(1), Cmp));
+          Cmp->getPredicate(),
+          LVI->getConstantRangeAtUse(Cmp->getOperandUse(0)),
+          LVI->getConstantRangeAtUse(Cmp->getOperandUse(1)));
 
   if (UnsignedPred == ICmpInst::Predicate::BAD_ICMP_PREDICATE)
     return false;
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
index c4f0ade39942a76..24acd528e6dcde5 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
@@ -1246,3 +1246,78 @@ declare <2 x i8> @llvm.umin.v2i8(<2 x i8>, <2 x i8>)
 declare <2 x i8> @llvm.umax.v2i8(<2 x i8>, <2 x i8>)
 
 attributes #4 = { noreturn }
+
+define i64 @test_select_flip(i64 noundef %arg) {
+; CHECK-LABEL: @test_select_flip(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ult i64 [[ARG:%.*]], 1000
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp ult i64 [[ARG]], 100
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[CMP1]], i1 [[CMP2]], i1 false
+; CHECK-NEXT:    br i1 [[SELECT]], label [[GOOD:%.*]], label [[BAD:%.*]]
+; CHECK:       bad:
+; CHECK-NEXT:    ret i64 1
+; CHECK:       good:
+; CHECK-NEXT:    ret i64 0
+;
+entry:
+  %cmp1 = icmp ult i64 %arg, 1000
+  %cmp2 = icmp slt i64 %arg, 100
+  %select = select i1 %cmp1, i1 %cmp2, i1 false
+  br i1 %select, label %good, label %bad
+
+bad:
+  ret i64 1
+
+good:
+  ret i64 0
+}
+
+define i64 @test_select_flip_fail1(i64 noundef %arg) {
+; CHECK-LABEL: @test_select_flip_fail1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i64 [[ARG:%.*]], 1000
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i64 [[ARG]], 100
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[CMP1]], i1 [[CMP2]], i1 false
+; CHECK-NEXT:    br i1 [[SELECT]], label [[GOOD:%.*]], label [[BAD:%.*]]
+; CHECK:       bad:
+; CHECK-NEXT:    ret i64 1
+; CHECK:       good:
+; CHECK-NEXT:    ret i64 0
+;
+entry:
+  %cmp1 = icmp slt i64 %arg, 1000
+  %cmp2 = icmp slt i64 %arg, 100
+  %select = select i1 %cmp1, i1 %cmp2, i1 false
+  br i1 %select, label %good, label %bad
+
+bad:
+  ret i64 1
+
+good:
+  ret i64 0
+}
+
+define i64 @test_select_flip_fail2(i64 noundef %arg) {
+; CHECK-LABEL: @test_select_flip_fail2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ult i64 [[ARG:%.*]], 1000
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i64 [[ARG]], 100
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[CMP1]], i1 false, i1 [[CMP2]]
+; CHECK-NEXT:    br i1 [[SELECT]], label [[GOOD:%.*]], label [[BAD:%.*]]
+; CHECK:       bad:
+; CHECK-NEXT:    ret i64 1
+; CHECK:       good:
+; CHECK-NEXT:    ret i64 0
+;
+entry:
+  %cmp1 = icmp ult i64 %arg, 1000
+  %cmp2 = icmp slt i64 %arg, 100
+  %select = select i1 %cmp1, i1 false, i1 %cmp2
+  br i1 %select, label %good, label %bad
+
+bad:
+  ret i64 1
+
+good:
+  ret i64 0
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/69948