[llvm] r216682 - On MachO, don't put non-private constants in mergeable sections.

[Rafael Espindola]

Author: rafael
Date: Thu Aug 28 15:13:31 2014
New Revision: 216682

URL: http://llvm.org/viewvc/llvm-project?rev=216682&view=rev
Log:
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.

Modified:
    llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
    llvm/trunk/test/CodeGen/X86/global-sections.ll

Modified: llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp?rev=216682&r1=216681&r2=216682&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (original)
+++ llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp Thu Aug 28 15:13:31 2014
@@ -626,7 +626,9 @@ SelectSectionForGlobal(const GlobalValue
           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())

Modified: llvm/trunk/test/CodeGen/X86/global-sections.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/global-sections.ll?rev=216682&r1=216681&r2=216682&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/global-sections.ll (original)
+++ llvm/trunk/test/CodeGen/X86/global-sections.ll Thu Aug 28 15:13:31 2014
@@ -53,21 +53,20 @@ define void @F1() {
 
 
 ; _Complex long long const G4 = 34;
- at G4 = unnamed_addr constant {i64,i64} { i64 34, i64 0 }
+ at 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.
+ at G15 = unnamed_addr constant i64 0
+
+; LINUX: .section        .rodata.cst8,"aM", at 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", at progbits,8
+; LINUX-SECTIONS: G15:
+
+; WIN32-SECTIONS: .section      .rdata,"rd",one_only,_G15
+; WIN32-SECTIONS: _G15: