From 8206257cb86b50f266df5988aa2604c836e1c95c Mon Sep 17 00:00:00 2001
From: David Stenberg <david.stenberg@ericsson.com>
Date: Thu, 20 Aug 2020 09:05:37 +0200
Subject: [PATCH] [GlobalOpt] Fix an incorrect Modified status

When removing a non-constant store to a global in
CleanupPointerRootUsers(), the GlobalOpt pass could incorrectly return
false.

This was caught using the check introduced by D80916.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D86149
---
 llvm/lib/Transforms/IPO/GlobalOpt.cpp              |  1 +
 .../test/Transforms/GlobalOpt/dead-store-status.ll | 43 ++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 llvm/test/Transforms/GlobalOpt/dead-store-status.ll

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index ee3b210..05d1465 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -268,6 +268,7 @@ CleanupPointerRootUsers(GlobalVariable *GV,
         I = J;
       } while (true);
       I->eraseFromParent();
+      Changed = true;
     }
   }
 
diff --git a/llvm/test/Transforms/GlobalOpt/dead-store-status.ll b/llvm/test/Transforms/GlobalOpt/dead-store-status.ll
new file mode 100644
index 0000000..afd1f9f
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/dead-store-status.ll
@@ -0,0 +1,43 @@
+; RUN: opt < %s -globalopt -S | FileCheck %s
+
+; When removing the store to @global in @foo, the pass would incorrectly return
+; false. This was caught by the pass return status check that is hidden under
+; EXPENSIVE_CHECKS.
+
+; CHECK: @global = internal unnamed_addr global i16* null, align 1
+
+; CHECK-LABEL: @foo
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret i16 undef
+
+@global = internal unnamed_addr global i16* null, align 1
+
+; Function Attrs: nofree noinline norecurse nounwind writeonly
+define i16 @foo(i16 %c) local_unnamed_addr #0 {
+entry:
+  %local1.addr = alloca i16, align 1
+  store i16* %local1.addr, i16** @global, align 1
+  ret i16 undef
+}
+
+; Function Attrs: noinline nounwind writeonly
+define i16 @bar() local_unnamed_addr #1 {
+entry:
+  %local2 = alloca [1 x i16], align 1
+  %0 = bitcast [1 x i16]* %local2 to i8*
+  call void @llvm.lifetime.start.p0i8(i64 1, i8* nonnull %0)
+  %arraydecay = getelementptr inbounds [1 x i16], [1 x i16]* %local2, i16 0, i16 0
+  store i16* %arraydecay, i16** @global, align 1
+  call void @llvm.lifetime.end.p0i8(i64 1, i8* nonnull %0)
+  ret i16 undef
+}
+
+; Function Attrs: argmemonly nounwind willreturn
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #2
+
+; Function Attrs: argmemonly nounwind willreturn
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #2
+
+attributes #0 = { nofree noinline norecurse nounwind writeonly }
+attributes #1 = { noinline nounwind writeonly }
+attributes #2 = { argmemonly nounwind willreturn }
-- 
2.7.4