[ConstraintElim] Fix miscompilation caused by PR97974 (#105790)

Fixes #105785.

(cherry picked from commit 85b6aac)

llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

@@ -1464,7 +1464,7 @@ static bool checkAndReplaceCmp(CmpIntrinsic *I, ConstraintInfo &Info,
     ToRemove.push_back(I);
     return true;
   }
-  if (checkCondition(ICmpInst::ICMP_EQ, LHS, RHS, I, Info)) {
+  if (checkCondition(ICmpInst::ICMP_EQ, LHS, RHS, I, Info).value_or(false)) {
     I->replaceAllUsesWith(ConstantInt::get(I->getType(), 0));
     ToRemove.push_back(I);
     return true;

llvm/test/Transforms/ConstraintElimination/pr105785.ll

@@ -0,0 +1,46 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=constraint-elimination -S %s | FileCheck %s
+
+define void @pr105785(ptr %p) {
+; CHECK-LABEL: define void @pr105785(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    br label %[[FOR_COND:.*]]
+; CHECK:       [[FOR_COND]]:
+; CHECK-NEXT:    [[FOR_IND:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ 1, %[[FOR_COND1:.*]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[FOR_IND]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label %[[FOR_COND1]], label %[[FOR_END6:.*]]
+; CHECK:       [[FOR_COND1]]:
+; CHECK-NEXT:    [[FOR_IND2:%.*]] = phi i32 [ [[INC:%.*]], %[[FOR_BODY3:.*]] ], [ 0, %[[FOR_COND]] ]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp ult i32 [[FOR_IND2]], 3
+; CHECK-NEXT:    br i1 [[CMP2]], label %[[FOR_BODY3]], label %[[FOR_COND]]
+; CHECK:       [[FOR_BODY3]]:
+; CHECK-NEXT:    [[SCMP:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[FOR_IND]], i32 1)
+; CHECK-NEXT:    store i32 [[SCMP]], ptr [[P]], align 4
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[FOR_IND2]], 1
+; CHECK-NEXT:    br label %[[FOR_COND1]]
+; CHECK:       [[FOR_END6]]:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.cond1, %entry
+  %for.ind = phi i32 [ 0, %entry ], [ 1, %for.cond1 ]
+  %cmp = icmp eq i32 %for.ind, 0
+  br i1 %cmp, label %for.cond1, label %for.end6
+
+for.cond1:                                        ; preds = %for.cond, %for.body3
+  %for.ind2 = phi i32 [ %inc, %for.body3 ], [ 0, %for.cond ]
+  %cmp2 = icmp ult i32 %for.ind2, 3
+  br i1 %cmp2, label %for.body3, label %for.cond
+
+for.body3:                                        ; preds = %for.cond1
+  %scmp = call i32 @llvm.scmp.i32.i32(i32 %for.ind, i32 1)
+  store i32 %scmp, ptr %p, align 4
+  %inc = add nuw nsw i32 %for.ind2, 1
+  br label %for.cond1
+
+for.end6:
+  ret void
+}