[PATCH] D65973: [InstSimplify] Report "Changed" also when only deleting dead instructions

[Bjorn Pettersson via Phabricator via llvm-commits]

bjope created this revision.
bjope added reviewers: spatel, chandlerc, foad.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

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 <https://reviews.llvm.org/rG02b9e45a7e4b815ca23608adad957ed1c7f8d03b>), since the code in question
was rewritten in that commit.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D65973

Files:
  llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
  llvm/test/Transforms/InstSimplify/remove-dead-call.ll


Index: llvm/test/Transforms/InstSimplify/remove-dead-call.ll
===================================================================
--- /dev/null
+++ 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 }
Index: llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
+++ llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
@@ -45,6 +45,7 @@
         // 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.


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