From 4fd5cd06c815724fa410c0bea276d919dea868c3 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 25 Mar 2014 06:14:26 +0000
Subject: [PATCH] WinCOFF: Add support for -fdata-sections

This is a pretty straight forward translation for COFF, we just need to
stick the data in a COMDAT section marked as
IMAGE_COMDAT_SELECT_NODUPLICATES.

N.B. We must be careful to avoid sticking entities with private linkage
in COMDAT groups.  COFF is pretty hostile to the renaming of entities so
we must be careful to disallow GlobalVariables with unstable names.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204703 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/TargetLoweringObjectFileImpl.cpp | 12 ++++++++---
 test/CodeGen/X86/global-sections.ll          | 22 ++++++++++++++------
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 8f113d79162..e41fbfc6d36 100644
--- a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -770,12 +770,18 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
                        Mangler &Mang, const TargetMachine &TM) const {
   // If we have -ffunction-sections then we should emit the global value to a
   // uniqued section specifically for it.
-  // TODO: Implement -fdata-sections.
-  bool EmitUniquedSection = Kind.isText() && TM.getFunctionSections();
+  bool EmitUniquedSection;
+  if (Kind.isText())
+    EmitUniquedSection = TM.getFunctionSections();
+  else
+    EmitUniquedSection = TM.getDataSections();
 
   // If this global is linkonce/weak and the target handles this by emitting it
   // into a 'uniqued' section name, create and return the section now.
-  if (GV->isWeakForLinker() || EmitUniquedSection) {
+  // Section names depend on the name of the symbol which is not feasible if the
+  // symbol has private linkage.
+  if ((GV->isWeakForLinker() || EmitUniquedSection) &&
+      !GV->hasPrivateLinkage()) {
     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
     unsigned Characteristics = getCOFFSectionFlags(Kind);
 
diff --git a/test/CodeGen/X86/global-sections.ll b/test/CodeGen/X86/global-sections.ll
index c768c303c87..5ad504719fc 100644
--- a/test/CodeGen/X86/global-sections.ll
+++ b/test/CodeGen/X86/global-sections.ll
@@ -3,8 +3,14 @@
 ; RUN: llc < %s -mtriple=i386-apple-darwin10 -relocation-model=static | FileCheck %s -check-prefix=DARWIN-STATIC
 ; RUN: llc < %s -mtriple=x86_64-apple-darwin10 | FileCheck %s -check-prefix=DARWIN64
 ; RUN: llc < %s -mtriple=i386-unknown-linux-gnu -fdata-sections | FileCheck %s -check-prefix=LINUX-SECTIONS
-; RUN: llc < %s -mtriple=i686-pc-win32 -ffunction-sections | FileCheck %s -check-prefix=WIN32-SECTIONS
+; RUN: llc < %s -mtriple=i686-pc-win32 -fdata-sections -ffunction-sections | FileCheck %s -check-prefix=WIN32-SECTIONS
 
+define void @F1() {
+  ret void
+}
+
+; WIN32-SECTIONS: .section        .text,"xr",one_only,_F1
+; WIN32-SECTIONS: .globl _F1
 
 ; int G1;
 @G1 = common global i32 0
@@ -42,6 +48,9 @@
 ; LINUX-SECTIONS: .section        .rodata.G3,"a",@progbits
 ; LINUX-SECTIONS: .globl  G3
 
+; WIN32-SECTIONS: .section        .rdata,"r",one_only,_G3
+; WIN32-SECTIONS: .globl  _G3
+
 
 ; _Complex long long const G4 = 34;
 @G4 = unnamed_addr constant {i64,i64} { i64 34, i64 0 }
@@ -118,6 +127,9 @@
 ; LINUX-SECTIONS: .section        .rodata.G7,"aMS",@progbits,1
 ; LINUX-SECTIONS:	.globl G7
 
+; WIN32-SECTIONS: .section        .rdata,"r",one_only,_G7
+; WIN32-SECTIONS:	.globl _G7
+
 
 @G8 = unnamed_addr constant [4 x i16] [ i16 1, i16 2, i16 3, i16 0 ]
 
@@ -178,9 +190,7 @@
 ; LINUX-SECTIONS:        .asciz  "foo"
 ; LINUX-SECTIONS:        .size   .LG14, 4
 
-define void @G15() {
-  ret void
-}
+; WIN32-SECTIONS:        .section        .rdata,"r"
+; WIN32-SECTIONS: L_G14:
+; WIN32-SECTIONS:        .asciz  "foo"
 
-; WIN32-SECTIONS: .section        .text,"xr",one_only,_G15
-; WIN32-SECTIONS: .globl _G15
-- 
2.34.1