[IndVars] Set Changed if sinkUnusedInvariants changes IR. PR38863

Currently, `sinkUnusedInvariants` does not set Changed flag even if it makes
changes in the IR. There is no clear evidence that it can cause a crash, but it
looks highly suspicious and likely invalid.

Differential Revision: https://reviews.llvm.org/D51777
Reviewed By: skatkov

llvm-svn: 341777

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/test/Transforms/IndVarSimplify/sink-from-preheader.ll b/llvm/test/Transforms/IndVarSimplify/sink-from-preheader.ll
new file mode 100644
index 00000000000..29e8b638281
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/sink-from-preheader.ll
@@ -0,0 +1,32 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -indvars -S | FileCheck %s
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin10.0"
+
+; We make sinking here, Changed flag should be set properly.
+define i32 @test(i32 %a, i32 %b, i32 %N) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[IV_NEXT]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[ADD:%.*]] = add i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    ret i32 [[ADD]]
+;
+entry:
+  %add = add i32 %a, %b
+  br label %loop
+
+loop:
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
+  %iv.next = add i32 %iv, 1
+  %cmp = icmp slt i32 %iv.next, %N
+  br i1 %cmp, label %loop, label %exit
+
+exit:
+  ret i32 %add
+}