[PATCH] Avoid internalizing dllexported symbols

[Yunzhong Gao]

ygao added you to the CC list for the revision "Avoid internalizing dllexported symbols".

Hi,
This patch teaches Internalize pass to skip dllexported symbols because they could be
referenced in a way that even the linker does not see. This is similar to r100269+r127138
for available_externally symbols.

Could someone take a look whether this is good to go in?
Thanks,
- Gao.

http://llvm-reviews.chandlerc.com/D2280

Files:
  test/Transforms/Internalize/lists.ll
  lib/Transforms/IPO/Internalize.cpp

Index: test/Transforms/Internalize/lists.ll
===================================================================
--- test/Transforms/Internalize/lists.ll
+++ test/Transforms/Internalize/lists.ll
@@ -48,3 +48,12 @@
 define available_externally void @bar() {
   ret void
 }
+
+; ALL: define dllexport void @export_foo() {
+; FOO_AND_J: define dllexport void @export_foo() {
+; FOO_AND_BAR: define dllexport void @export_foo() {
+; FOO_J_AND_BAR: define dllexport void @export_foo() {
+define dllexport void @export_foo() {
+  ret void
+}
+
Index: lib/Transforms/IPO/Internalize.cpp
===================================================================
--- lib/Transforms/IPO/Internalize.cpp
+++ lib/Transforms/IPO/Internalize.cpp
@@ -115,6 +115,10 @@
   if (GV.hasAvailableExternallyLinkage())
     return false;
 
+  // Assume that dllexported symbols are referenced elsewhere
+  if (GV.hasDLLExportLinkage())
+    return false;
+
   // Already has internal linkage
   if (GV.hasLocalLinkage())
     return false;
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