[PATCH] D20078: PGO] Fix __llvm_profile_raw_version linkage in MACHO

[Rong Xu via llvm-commits]

xur created this revision.
xur added reviewers: vsk, davidxl.
xur added subscribers: llvm-commits, xur.

IR instrumentation generates a COMDAT symbol __llvm_profile_raw_version to overwrite the same symbol in profile run-time to distinguish IR profiles from Clang generated profiles. In MACHO, LinkOnceODR linkage is used due to the lack of COMDAT support.

But LinkOnceODR linkage might have .weak_def_can_be_hidden assembly directive, while the weak variable in run-time has a .weak_definition directive. Linker will not merge these two symbols even they have  the same name. The end result is IR profiles are not properly flagged in MACHO.

This patch changes the linkage for __llvm_profile_raw_version in each module to LinkOnceAny so that it has same .weak_definition directive as in  the run-time..


http://reviews.llvm.org/D20078

Files:
  lib/Transforms/Instrumentation/PGOInstrumentation.cpp
  test/Transforms/PGOProfile/macho.ll

Index: test/Transforms/PGOProfile/macho.ll
===================================================================
--- test/Transforms/PGOProfile/macho.ll
+++ test/Transforms/PGOProfile/macho.ll
@@ -0,0 +1,9 @@
+; RUN: opt < %s -mtriple=x86_64-apple-macosx10.11.0 -pgo-instr-gen -instrprof -S | llc | FileCheck %s --check-prefix=MACHO-DIRECTIVE
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; MACHO-DIRECTIVE: .weak_definition        ___llvm_profile_raw_version
+define i32 @test_macho(i32 %i) {
+entry:
+  ret i32 %i
+}
Index: lib/Transforms/Instrumentation/PGOInstrumentation.cpp
===================================================================
--- lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -776,7 +776,7 @@
   IRLevelVersionVariable->setVisibility(GlobalValue::DefaultVisibility);
   Triple TT(M.getTargetTriple());
   if (TT.isOSBinFormatMachO())
-    IRLevelVersionVariable->setLinkage(GlobalValue::LinkOnceODRLinkage);
+    IRLevelVersionVariable->setLinkage(GlobalValue::LinkOnceAnyLinkage);
   else
     IRLevelVersionVariable->setComdat(M.getOrInsertComdat(
         StringRef(INSTR_PROF_QUOTE(IR_LEVEL_PROF_VERSION_VAR))));


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