[llvm] r306368 - [Reassociate] Make sure EraseInst sets MadeChange

[Mikael Holmen via llvm-commits]

Author: uabelho
Date: Mon Jun 26 22:32:13 2017
New Revision: 306368

URL: http://llvm.org/viewvc/llvm-project?rev=306368&view=rev
Log:
[Reassociate] Make sure EraseInst sets MadeChange

Summary:
EraseInst didn't report that it made IR changes through MadeChange.

It is essential that changes to the IR are reported correctly,
since for example ReassociatePass::run() will indicate that all
analyses are preserved otherwise.
And the CGPassManager determines if the CallGraph is up-to-date
based on status from InstructionCombiningPass::runOnFunction().

Reviewers: craig.topper, rnk, davide

Reviewed By: rnk, davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34616

Added:
    llvm/trunk/test/Transforms/Reassociate/erase_inst_made_change.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp?rev=306368&r1=306367&r2=306368&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp Mon Jun 26 22:32:13 2017
@@ -1894,6 +1894,8 @@ void ReassociatePass::EraseInst(Instruct
         Op = Op->user_back();
       RedoInsts.insert(Op);
     }
+
+  MadeChange = true;
 }
 
 // Canonicalize expressions of the following form:

Added: llvm/trunk/test/Transforms/Reassociate/erase_inst_made_change.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Reassociate/erase_inst_made_change.ll?rev=306368&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/Reassociate/erase_inst_made_change.ll (added)
+++ llvm/trunk/test/Transforms/Reassociate/erase_inst_made_change.ll Mon Jun 26 22:32:13 2017
@@ -0,0 +1,29 @@
+; RUN: opt < %s -inline -reassociate -S | FileCheck %s
+
+; This test case exposed a bug in reassociate where EraseInst's
+; removal of a dead call wasn't recognized as changing the IR.
+; So when runOnFunction propagated the "made changes" upwards
+; to the CallGraphSCCPass it signalled that no changes had been
+; made, so CallGraphSCCPass assumed that the old CallGraph,
+; as known by that pass manager, still was up-to-date.
+;
+; This was detected as an assert when trying to remove the
+; no longer used function 'bar' (due to incorrect reference
+; count in the CallGraph).
+
+define void @foo() {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret void
+entry:
+  call void @bar()
+  ret void
+}
+
+define internal void @bar() noinline nounwind readnone {
+; CHECK-NOT: bar
+entry:
+  ret void
+}
+
+