[PATCH] D15323: Add Available Externally linkage type to isWeakForLinker()

[Mehdi AMINI via llvm-commits]

joker.eph created this revision.
joker.eph added reviewers: rafael, echristo.
joker.eph added a subscriber: llvm-commits.

Per LangRef: "Globals with available_externally linkage are
allowed to be discarded at will, and are otherwise the same
as linkonce_odr", since linkonce_odr is in this list it makes
sense to have available_externally there as well.

http://reviews.llvm.org/D15323

Files:
  include/llvm/IR/GlobalValue.h
  test/Transforms/GlobalOpt/available_externally_global_ctors.ll

Index: test/Transforms/GlobalOpt/available_externally_global_ctors.ll
===================================================================
--- /dev/null
+++ test/Transforms/GlobalOpt/available_externally_global_ctors.ll
@@ -0,0 +1,23 @@
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+; RUN: opt -S -globalopt < %s | FileCheck %s
+
+; Verify that the initialization of the available_externally global is not eliminated
+; CHECK: @llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @foo_static_init, i8* null }]
+
+ at llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @foo_static_init, i8* null }]
+ at foo_external = available_externally global void ()* null, align 8
+
+define internal void @foo_static_init() {
+entry:
+  store void ()* @foo_impl, void ()** @foo_external, align 8
+  ret void
+}
+
+; Function Attrs: norecurse nounwind readnone ssp uwtable
+define internal void @foo_impl() #0 {
+entry:
+  ret void
+}
+
Index: include/llvm/IR/GlobalValue.h
===================================================================
--- include/llvm/IR/GlobalValue.h
+++ include/llvm/IR/GlobalValue.h
@@ -256,7 +256,8 @@
   static bool isWeakForLinker(LinkageTypes Linkage)  {
     return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage ||
            Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage ||
-           Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
+           Linkage == CommonLinkage || Linkage == ExternalWeakLinkage ||
+           Linkage == AvailableExternallyLinkage;
   }
 
   bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }


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