[MachO] Emit Weak ReadOnlyWithRel to ConstDataSection

Summary:
Darwin dynamic linker can handle weak symbols in ConstDataSection.
ReadonReadOnlyWithRel symbols should be emitted in ConstDataSection
instead of normal DataSection.

rdar://problem/39298457

Reviewers: dexonsmith, kledzik

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45472

llvm-svn: 329752

include/llvm/MC/MCObjectFileInfo.h

@@ -183,6 +183,7 @@ protected:
   MCSection *ConstTextCoalSection;
   MCSection *ConstDataSection;
   MCSection *DataCoalSection;
+  MCSection *ConstDataCoalSection;
   MCSection *DataCommonSection;
   MCSection *DataBSSSection;
   MCSection *FourByteConstantSection;
@@ -328,6 +329,9 @@ public:
   }
   const MCSection *getConstDataSection() const { return ConstDataSection; }
   const MCSection *getDataCoalSection() const { return DataCoalSection; }
+  const MCSection *getConstDataCoalSection() const {
+    return ConstDataCoalSection;
+  }
   const MCSection *getDataCommonSection() const { return DataCommonSection; }
   MCSection *getDataBSSSection() const { return DataBSSSection; }
   const MCSection *getFourByteConstantSection() const {

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -744,6 +744,8 @@ MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
   if (GO->isWeakForLinker()) {
     if (Kind.isReadOnly())
       return ConstTextCoalSection;
+    if (Kind.isReadOnlyWithRel())
+      return ConstDataCoalSection;
     return DataCoalSection;
   }
 

lib/MC/MCObjectFileInfo.cpp

@@ -135,6 +135,10 @@ void MCObjectFileInfo::initMachOMCObjectFileInfo(const Triple &T) {
   // "__DATA/__datacoal_nt" => section "__DATA/__data"
   Triple::ArchType ArchTy = T.getArch();
 
+  ConstDataSection  // .const_data
+    = Ctx->getMachOSection("__DATA", "__const", 0,
+                           SectionKind::getReadOnlyWithRel());
+
   if (ArchTy == Triple::ppc || ArchTy == Triple::ppc64) {
     TextCoalSection
       = Ctx->getMachOSection("__TEXT", "__textcoal_nt",
@@ -147,15 +151,14 @@ void MCObjectFileInfo::initMachOMCObjectFileInfo(const Triple &T) {
                              SectionKind::getReadOnly());
     DataCoalSection = Ctx->getMachOSection(
         "__DATA", "__datacoal_nt", MachO::S_COALESCED, SectionKind::getData());
+    ConstDataCoalSection = DataCoalSection;
   } else {
     TextCoalSection = TextSection;
     ConstTextCoalSection = ReadOnlySection;
     DataCoalSection = DataSection;
+    ConstDataCoalSection = ConstDataSection;
   }
 
-  ConstDataSection  // .const_data
-    = Ctx->getMachOSection("__DATA", "__const", 0,
-                           SectionKind::getReadOnlyWithRel());
   DataCommonSection
     = Ctx->getMachOSection("__DATA","__common",
                            MachO::S_ZEROFILL,

test/CodeGen/X86/global-sections.ll

@@ -329,3 +329,8 @@ bb7:
 ; WIN32-SECTIONS: .section	.bss,"bw",one_only,_G17
 ; WIN32-SECTIONS: _G17:
 ; WIN32-SECTIONS:.byte	0
+
+; check weak ReadOnlyWithRel globals.
+@G18 = linkonce_odr unnamed_addr constant i64* @G15
+; DARWIN64: .section      __DATA,__const
+; DARWIN64: _G18: