From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 11 Aug 2017 23:52:28 +0000 (+0000)
Subject: D36604: PR34148: Do not assume we can use a copy relocation for an `external_weak... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f604fb5d6e2ed2553fd52fd3ce540e706b2f9bbe;p=llvm

D36604: PR34148: Do not assume we can use a copy relocation for an `external_weak` global

An `external_weak` global may be intended to resolve as a null pointer if it's
not defined, so it doesn't make sense to use a copy relocation for it.

Differential Revision: https://reviews.llvm.org/D36604


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310773 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/TargetMachine.cpp b/lib/Target/TargetMachine.cpp
index e8fe0a2b218..b2578fb7a02 100644
--- a/lib/Target/TargetMachine.cpp
+++ b/lib/Target/TargetMachine.cpp
@@ -154,8 +154,9 @@ bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
       return true;
 
     bool IsTLS = GV && GV->isThreadLocal();
-    bool IsAccessViaCopyRelocs =
-        Options.MCOptions.MCPIECopyRelocations && GV && isa<GlobalVariable>(GV);
+    bool IsAccessViaCopyRelocs = Options.MCOptions.MCPIECopyRelocations && GV &&
+                                 isa<GlobalVariable>(GV) &&
+                                 !GV->hasExternalWeakLinkage();
     Triple::ArchType Arch = TT.getArch();
     bool IsPPC =
         Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
diff --git a/test/CodeGen/X86/global-access-pie-copyrelocs.ll b/test/CodeGen/X86/global-access-pie-copyrelocs.ll
index b0ecf3e942e..b370c4eeca9 100644
--- a/test/CodeGen/X86/global-access-pie-copyrelocs.ll
+++ b/test/CodeGen/X86/global-access-pie-copyrelocs.ll
@@ -63,6 +63,20 @@ entry:
   ret i32 %0
 }
 
+; ExternalWeak Linkage
+@e = extern_weak global i32, align 4
+
+define i32* @my_access_global_d() #0 {
+; X32-LABEL: my_access_global_d:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32:       movl e@GOT(%eax), %eax
+; X64-LABEL: my_access_global_d:
+; X64:       movq e@GOTPCREL(%rip), %rax
+
+entry:
+  ret i32* @e
+}
+
 ; External Linkage, only declaration, store a value.
 
 define i32 @my_access_global_store_d() #0 {