From 2bfef929c01800ec65de1f681f9af1bfed14ea81 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Wed, 17 Sep 2014 20:41:13 +0000
Subject: [PATCH] Internalize common symbols when we can.

This fixes pr20974.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217981 91177308-0d34-0410-b5e6-96231b3b80d8
---
 test/tools/gold/common.ll  | 18 ++++++++++++++++++
 tools/gold/gold-plugin.cpp |  4 +++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/test/tools/gold/common.ll b/test/tools/gold/common.ll
index 77976c84495..f3092310a1d 100644
--- a/test/tools/gold/common.ll
+++ b/test/tools/gold/common.ll
@@ -8,4 +8,22 @@
 
 @a = common global i8 0, align 8
 
+; Shared library case, we merge @a as common and keep it for the symbol table.
 ; CHECK: @a = common global i16 0, align 8
+
+; RUN: ld -plugin %llvmshlibdir/LLVMgold.so \
+; RUN:    --plugin-opt=emit-llvm \
+; RUN:    %t1.o %t2.o -o %t3.o
+; RUN: llvm-dis %t3.o -o - | FileCheck --check-prefix=EXEC %s
+
+; All IR case, we internalize a after merging.
+; EXEC: @a = internal global i16 0, align 8
+
+; RUN: llc %p/Inputs/common.ll -o %t2.o -filetype=obj
+; RUN: ld -plugin %llvmshlibdir/LLVMgold.so \
+; RUN:    --plugin-opt=emit-llvm \
+; RUN:    %t1.o %t2.o -o %t3.o
+; RUN: llvm-dis %t3.o -o - | FileCheck --check-prefix=MIXED %s
+
+; Mixed ELF and IR. We keep ours as common so the linker will finish the merge.
+; MIXED: @a = common global i8 0, align 8
diff --git a/tools/gold/gold-plugin.cpp b/tools/gold/gold-plugin.cpp
index abe6e4dd66b..95f7e32a611 100644
--- a/tools/gold/gold-plugin.cpp
+++ b/tools/gold/gold-plugin.cpp
@@ -578,10 +578,12 @@ getModuleForFile(LLVMContext &Context, claimed_file &F, raw_fd_ostream *ApiFile,
     if (!GV)
       continue; // Asm symbol.
 
-    if (GV->hasCommonLinkage()) {
+    if (Resolution != LDPR_PREVAILING_DEF_IRONLY && GV->hasCommonLinkage()) {
       // Common linkage is special. There is no single symbol that wins the
       // resolution. Instead we have to collect the maximum alignment and size.
       // The IR linker does that for us if we just pass it every common GV.
+      // We still have to keep track of LDPR_PREVAILING_DEF_IRONLY so we
+      // internalize once the IR linker has done its job.
       continue;
     }