From: Duncan P. N. Exon Smith <dexonsmith@apple.com>
Date: Thu, 20 Mar 2014 22:50:08 +0000 (+0000)
Subject: PGO: Don't define instrumentation data available_externally
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=81e3346e95b2e3f65e894f5e31d1a8141a4bbace;p=clang

PGO: Don't define instrumentation data available_externally

Variables with available_externally linkage can be dropped at will.
This causes link errors, since there are still references to the
instrumentation!  linkonce_odr is almost equivalent, so use that
instead.

As a drive-by fix (I don't have an Elf system, so I'm not sure how to
write a testcase), use linkonce linkage for the instrumentation of
extern_weak functions.

<rdar://problem/15943240>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204408 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CodeGenPGO.cpp b/lib/CodeGen/CodeGenPGO.cpp
index 0dfecfc36c..99109f42e4 100644
--- a/lib/CodeGen/CodeGenPGO.cpp
+++ b/lib/CodeGen/CodeGenPGO.cpp
@@ -824,7 +824,22 @@ void CodeGenPGO::assignRegionCounters(const Decl *D, llvm::Function *Fn) {
   if (!D)
     return;
   setFuncName(Fn);
+
+  // Set the linkage for variables based on the function linkage.  Usually, we
+  // want to match it, but available_externally and extern_weak both have the
+  // wrong semantics.
   VarLinkage = Fn->getLinkage();
+  switch (VarLinkage) {
+  case llvm::GlobalValue::ExternalWeakLinkage:
+    VarLinkage = llvm::GlobalValue::LinkOnceAnyLinkage;
+    break;
+  case llvm::GlobalValue::AvailableExternallyLinkage:
+    VarLinkage = llvm::GlobalValue::LinkOnceODRLinkage;
+    break;
+  default:
+    break;
+  }
+
   mapRegionCounters(D);
   if (InstrumentRegions)
     emitCounterVariables();
diff --git a/test/Profile/c-linkage-available_externally.c b/test/Profile/c-linkage-available_externally.c
new file mode 100644
index 0000000000..cbdf306c82
--- /dev/null
+++ b/test/Profile/c-linkage-available_externally.c
@@ -0,0 +1,12 @@
+// Make sure instrementation data from available_externally functions doesn't
+// get thrown out.
+// RUN: %clang_cc1 -O2 -triple x86_64-apple-macosx10.9 -main-file-name c-linkage-available_externally.c %s -o - -emit-llvm -fprofile-instr-generate | FileCheck %s
+
+// CHECK: @__llvm_profile_counters_foo = linkonce_odr global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
+// CHECK: @__llvm_profile_name_foo = linkonce_odr constant [3 x i8] c"foo", section "__DATA,__llvm_prf_names", align 1
+// CHECK: @__llvm_profile_data_foo = linkonce_odr constant { i32, i32, i64, i8*, i64* } { i32 3, i32 1, i64 1, i8* getelementptr inbounds ([3 x i8]* @__llvm_profile_name_foo, i32 0, i32 0), i64* getelementptr inbounds ([1 x i64]* @__llvm_profile_counters_foo, i32 0, i32 0) }, section "__DATA,__llvm_prf_data", align 8
+inline int foo(void) { return 1; }
+
+int main(void) {
+  return foo();
+}