[PATCH] Don't localize globals that may serve as leak checker roots.

[Alexey Samsonov]

Hi nicholas,

This change prevents GlobalOpt from turning globals into
stack-allocated locals, if these variables may serve as a leak checker
root. For instance, transforming
  Foo *x;
  int main() { x = new Foo(); }
into
  int main() { Foo *x = new Foo(); }
will make LeakSanitizer treat "x" as definitely leaked, which is
undesirable.

http://llvm-reviews.chandlerc.com/D1754

Files:
  test/Transforms/GlobalOpt/metadata.ll
  test/Transforms/GlobalOpt/dont-localize-pointer.ll
  lib/Transforms/IPO/GlobalOpt.cpp

Index: test/Transforms/GlobalOpt/metadata.ll
===================================================================
--- test/Transforms/GlobalOpt/metadata.ll
+++ test/Transforms/GlobalOpt/metadata.ll
@@ -3,24 +3,24 @@
 ; PR6112 - When globalopt does RAUW(@G, %G), the metadata reference should drop
 ; to null.  Function local metadata that references @G from a different function
 ; to that containing %G should likewise drop to null.
- at G = internal global i8** null
+ at G = internal global i32 0
 
 define i32 @main(i32 %argc, i8** %argv) {
 ; CHECK-LABEL: @main(
 ; CHECK: %G = alloca
-  store i8** %argv, i8*** @G
+  store i32 %argc, i32* @G
   ret i32 0
 }
 
 define void @foo(i32 %x) {
-  call void @llvm.foo(metadata !{i8*** @G, i32 %x})
+  call void @llvm.foo(metadata !{i32* @G, i32 %x})
 ; CHECK: call void @llvm.foo(metadata !{null, i32 %x})
   ret void
 }
 
 declare void @llvm.foo(metadata) nounwind readnone
 
 !named = !{!0}
 
-!0 = metadata !{i8*** @G}
+!0 = metadata !{i32* @G}
 ; CHECK: !0 = metadata !{null}
Index: test/Transforms/GlobalOpt/dont-localize-pointer.ll
===================================================================
--- /dev/null
+++ test/Transforms/GlobalOpt/dont-localize-pointer.ll
@@ -0,0 +1,10 @@
+; RUN: opt -S -globalopt < %s | FileCheck %s
+
+ at G = internal global i8** null
+
+define i32 @main(i32 %argc, i8** %argv) {
+; CHECK-LABEL: @main(
+; CHECK-NOT: alloca
+  store i8** %argv, i8*** @G
+  ret i32 0
+}
Index: lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- lib/Transforms/IPO/GlobalOpt.cpp
+++ lib/Transforms/IPO/GlobalOpt.cpp
@@ -1951,7 +1951,8 @@
       GV->getType()->getElementType()->isSingleValueType() &&
       GS.AccessingFunction->getName() == "main" &&
       GS.AccessingFunction->hasExternalLinkage() &&
-      GV->getType()->getAddressSpace() == 0) {
+      GV->getType()->getAddressSpace() == 0 &&
+      !isLeakCheckerRoot(GV)) {
     DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
     Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction
                                                    ->getEntryBlock().begin());
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D1754.1.patch
Type: text/x-patch
Size: 2156 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20130925/049e5cbb/attachment.bin>