[GVN] Add another test for phi translation miscompile (NFC)

Author: nikic

llvm/test/Transforms/GVN/phi-translation-to-wrong-context.ll

@@ -0,0 +1,60 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -gvn < %s | FileCheck %s
+
+; FIXME
+; Phi translation of %gep.j cannot use %gep.i, which is located in a context
+; where %i != 0, and would result in incorrect NoAlias results in a context
+; where %i == 0 may hold.
+
+define i32 @test(i64 %i, i1 %c1, i1 %c2) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[PTR:%.*]] = alloca [2 x i32], align 4
+; CHECK-NEXT:    br i1 [[C1:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
+; CHECK:       if:
+; CHECK-NEXT:    br i1 [[C2:%.*]], label [[IF2:%.*]], label [[ELSE2:%.*]]
+; CHECK:       if2:
+; CHECK-NEXT:    store i32 1, ptr [[PTR]], align 4
+; CHECK-NEXT:    br label [[JOIN:%.*]]
+; CHECK:       else2:
+; CHECK-NEXT:    store i32 2, ptr [[PTR]], align 4
+; CHECK-NEXT:    br label [[JOIN]]
+; CHECK:       join:
+; CHECK-NEXT:    [[J:%.*]] = phi i64 [ [[I:%.*]], [[IF2]] ], [ 0, [[ELSE2]] ]
+; CHECK-NEXT:    [[GEP_J:%.*]] = getelementptr inbounds i32, ptr [[PTR]], i64 [[J]]
+; CHECK-NEXT:    ret i32 2
+; CHECK:       else:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i64 [[I]], 0
+; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
+; CHECK-NEXT:    [[GEP_I:%.*]] = getelementptr inbounds i32, ptr [[PTR]], i64 [[I]]
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %ptr = alloca [2 x i32]
+  br i1 %c1, label %if, label %else
+
+if:
+  br i1 %c2, label %if2, label %else2
+
+if2:
+  store i32 1, ptr %ptr
+  br label %join
+
+else2:
+  store i32 2, ptr %ptr
+  br label %join
+
+join:
+  %j = phi i64 [ %i, %if2 ], [ 0, %else2 ]
+  %gep.j = getelementptr inbounds i32, ptr %ptr, i64 %j
+  %v = load i32, ptr %gep.j
+  ret i32 %v
+
+else:
+  %cmp = icmp ne i64 %i, 0
+  call void @llvm.assume(i1 %cmp)
+  %gep.i = getelementptr inbounds i32, ptr %ptr, i64 %i
+  ret i32 0
+}
+
+declare void @llvm.assume(i1)