From 882e2c92690ad84249873bcb6dc2bd8af6c280dc Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Thu, 8 Nov 2018 03:57:55 +0000
Subject: [PATCH] [MergeFuncs] Call removeUsers() prior to unnamed_addr RAUW

Summary:
For unnamed_addr functions we RAUW instead of only replacing direct callers. However, functions in which replacements were performed currently are not added back to the worklist, resulting in missed merging opportunities.

Fix this by calling removeUsers() prior to RAUW.

Reviewers: jfb, whitequark

Reviewed By: whitequark

Subscribers: rkruppe, llvm-commits

Differential Revision: https://reviews.llvm.org/D53262

llvm-svn: 346385
---
 lib/Transforms/IPO/MergeFunctions.cpp         |  1 +
 .../MergeFunc/unnamed-addr-reprocessing.ll    | 35 +++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 test/Transforms/MergeFunc/unnamed-addr-reprocessing.ll

diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index e8056e6cc61..49b3eacbaff 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -770,6 +770,7 @@ void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
         GlobalNumbers.erase(G);
         // If G's address is not significant, replace it entirely.
         Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
+        removeUsers(G);
         G->replaceAllUsesWith(BitcastF);
       } else {
         // Redirect direct callers of G to F. (See note on MergeFunctionsPDI
diff --git a/test/Transforms/MergeFunc/unnamed-addr-reprocessing.ll b/test/Transforms/MergeFunc/unnamed-addr-reprocessing.ll
new file mode 100644
index 00000000000..5902edc0e88
--- /dev/null
+++ b/test/Transforms/MergeFunc/unnamed-addr-reprocessing.ll
@@ -0,0 +1,35 @@
+; RUN: opt -S -mergefunc < %s | FileCheck %s
+
+; After test3 and test4 have been merged, we should detect that
+; test1 and test2 can also be merged.
+
+; CHECK: define void @test4() unnamed_addr
+; CHECK-NEXT: tail call void @test3()
+; CHECK: define void @test2() unnamed_addr
+; CHECK-NEXT: tail call void @test1()
+
+declare void @dummy()
+  
+define void @test1() unnamed_addr {
+    call void @test3()
+    call void @test3()
+    ret void
+}
+
+define void @test2() unnamed_addr {
+    call void @test4()
+    call void @test4()
+    ret void
+}
+
+define void @test3() unnamed_addr {
+    call void @dummy()
+    call void @dummy()
+    ret void
+}
+
+define void @test4() unnamed_addr {
+    call void @dummy()
+    call void @dummy()
+    ret void
+}