[InstSimplify] Report "Changed" also when only deleting dead instructions

Summary:
Make sure that we report that changes has been made
by InstSimplify also in situations when only trivially
dead instructions has been removed. If for example a call
is removed the call graph must be updated.

Bug seem to have been introduced by llvm-svn r367173
(commit 02b9e45a7e4b81), since the code in question
was rewritten in that commit.

Reviewers: spatel, chandlerc, foad

Reviewed By: spatel

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65973

llvm-svn: 368401

2 files changed, 29 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp b/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
index c31d0e74641..920b12b8a6a 100644
--- a/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
+++ b/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
@@ -45,6 +45,7 @@ static bool runImpl(Function &F, const SimplifyQuery &SQ,
         // Don't waste time simplifying dead/unused instructions.
         if (isInstructionTriviallyDead(&I)) {
           DeadInstsInBB.push_back(&I);
+          Changed = true;
         } else if (!I.use_empty()) {
           if (Value *V = SimplifyInstruction(&I, SQ, ORE)) {
             // Mark all uses for resimplification next time round the loop.
diff --git a/llvm/test/Transforms/InstSimplify/remove-dead-call.ll b/llvm/test/Transforms/InstSimplify/remove-dead-call.ll
new file mode 100755
index 00000000000..172a9913115
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/remove-dead-call.ll
@@ -0,0 +1,28 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instsimplify -S -o /dev/null -debug-pass=Details 2>&1 | FileCheck --check-prefix DETAILS %s
+; RUN: opt < %s -instsimplify -S -o - | FileCheck %s
+
+; Verify that InstSimplifyLegacyPass notifies the pass manager about changes
+; being made (when a call is removed CGSCC must be updated).
+;
+; DETAILS: Made Modification 'Remove redundant instructions' on Function 'main'
+
+define internal void @func_1(i64* nocapture readnone %0) #0 {
+; CHECK-LABEL: @func_1(
+; CHECK-NEXT:    unreachable
+;
+  unreachable
+}
+
+define i16 @main(i16 %0, i16** nocapture readnone %1) #1 {
+; CHECK-LABEL: @main(
+; CHECK-NEXT:  bb1:
+; CHECK-NEXT:    unreachable
+;
+bb1:
+  call void @func_1(i64* undef)
+  unreachable
+}
+
+attributes #0 = { noinline norecurse nounwind readnone }
+attributes #1 = { norecurse nounwind readnone }