From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Thu, 28 Aug 2014 20:13:31 +0000 (+0000)
Subject: On MachO, don't put non-private constants in mergeable sections.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4bb535027e3c270e32631970e89afdfd2ded9fb1;p=oota-llvm.git

On MachO, don't put non-private constants in mergeable sections.

On MachO, putting a symbol that doesn't start with a 'L' or 'l' in one of the
__TEXT,__literal* sections prevents the linker from merging the context of the
section.

Since private GVs are the ones the get mangled to start with 'L' or 'l', we now
only put those on the __TEXT,__literal* sections.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216682 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 55e175680be..8820d10a0c6 100644
--- a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -626,7 +626,9 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
           cast<GlobalVariable>(GV)) < 32)
     return UStringSection;
 
-  if (Kind.isMergeableConst()) {
+  // With MachO only variables whose corresponding symbol starts with 'l' or
+  // 'L' can be merged, so we only try merging GVs with private linkage.
+  if (GV->hasPrivateLinkage() && Kind.isMergeableConst()) {
     if (Kind.isMergeableConst4())
       return FourByteConstantSection;
     if (Kind.isMergeableConst8())
diff --git a/test/CodeGen/X86/global-sections.ll b/test/CodeGen/X86/global-sections.ll
index c763f3947e5..fa1169d8a8e 100644
--- a/test/CodeGen/X86/global-sections.ll
+++ b/test/CodeGen/X86/global-sections.ll
@@ -53,21 +53,20 @@ define void @F1() {
 
 
 ; _Complex long long const G4 = 34;
-@G4 = unnamed_addr constant {i64,i64} { i64 34, i64 0 }
+@G4 = private unnamed_addr constant {i64,i64} { i64 34, i64 0 }
 
 ; DARWIN: .section        __TEXT,__literal16,16byte_literals
-; DARWIN: _G4:
+; DARWIN: L_G4:
 ; DARWIN:     .long 34
 
 ; DARWIN-STATIC: .section        __TEXT,__literal16,16byte_literals
-; DARWIN-STATIC: _G4:
+; DARWIN-STATIC: L_G4:
 ; DARWIN-STATIC:     .long 34
 
 ; DARWIN64: .section        __TEXT,__literal16,16byte_literals
-; DARWIN64: _G4:
+; DARWIN64: L_G4:
 ; DARWIN64:     .quad 34
 
-
 ; int G5 = 47;
 @G5 = global i32 47
 
@@ -194,3 +193,23 @@ define void @F1() {
 ; WIN32-SECTIONS: L_G14:
 ; WIN32-SECTIONS:        .asciz  "foo"
 
+; cannot be merged on MachO, but can on other formats.
+@G15 = unnamed_addr constant i64 0
+
+; LINUX: .section        .rodata.cst8,"aM",@progbits,8
+; LINUX: G15:
+
+; DARWIN: .section      __TEXT,__const
+; DARWIN: _G15:
+
+; DARWIN-STATIC: .section       __TEXT,__const
+; DARWIN-STATIC: _G15:
+
+; DARWIN64: .section       __TEXT,__const
+; DARWIN64: _G15:
+
+; LINUX-SECTIONS: .section      .rodata.G15,"aM",@progbits,8
+; LINUX-SECTIONS: G15:
+
+; WIN32-SECTIONS: .section      .rdata,"rd",one_only,_G15
+; WIN32-SECTIONS: _G15: