[AsmPrinter][TLOF] ARM64 MachO support for replacing GOT equivalents

Follow up r230264 and add ARM64 support for replacing global GOT
equivalent symbol accesses by references to the GOT entry for the final
symbol instead, example:

-- before

   .globl  _foo
  _foo:
   .long   42

   .globl  _gotequivalent
  _gotequivalent:
   .quad   _foo

   .globl  _delta
  _delta:
   .long   _gotequivalent-_delta

-- after

   .globl  _foo
  _foo:
   .long   42

   .globl  _delta
  Ltmp3:
   .long _foo@GOT-Ltmp3

llvm-svn: 231474

2 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
index 4069038dffe..3c0a3428ff3 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
@@ -23,6 +23,12 @@ void AArch64_ELFTargetObjectFile::Initialize(MCContext &Ctx,
   InitializeELF(TM.Options.UseInitArray);
 }
 
+AArch64_MachoTargetObjectFile::AArch64_MachoTargetObjectFile()
+  : TargetLoweringObjectFileMachO() {
+  SupportIndirectSymViaGOTPCRel = true;
+  SupportGOTPCRelWithOffset = false;
+}
+
 const MCExpr *AArch64_MachoTargetObjectFile::getTTypeGlobalReference(
     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
     const TargetMachine &TM, MachineModuleInfo *MMI,
@@ -50,3 +56,15 @@ MCSymbol *AArch64_MachoTargetObjectFile::getCFIPersonalitySymbol(
     MachineModuleInfo *MMI) const {
   return TM.getSymbol(GV, Mang);
 }
+
+const MCExpr *AArch64_MachoTargetObjectFile::getIndirectSymViaGOTPCRel(
+    const MCSymbol *Sym, int64_t Offset, MCStreamer &Streamer) const {
+  // On ARM64 Darwin, we can reference symbols with foo@GOT-., which
+  // is an indirect pc-relative reference.
+  const MCExpr *Res =
+      MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOT, getContext());
+  MCSymbol *PCSym = getContext().CreateTempSymbol();
+  Streamer.EmitLabel(PCSym);
+  const MCExpr *PC = MCSymbolRefExpr::Create(PCSym, getContext());
+  return MCBinaryExpr::CreateSub(Res, PC, getContext());
+}
diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
index 2e595f91961..067fda5952b 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
@@ -24,6 +24,8 @@ class AArch64_ELFTargetObjectFile : public TargetLoweringObjectFileELF {
 /// AArch64_MachoTargetObjectFile - This TLOF implementation is used for Darwin.
 class AArch64_MachoTargetObjectFile : public TargetLoweringObjectFileMachO {
 public:
+  AArch64_MachoTargetObjectFile();
+
   const MCExpr *getTTypeGlobalReference(const GlobalValue *GV,
                                         unsigned Encoding, Mangler &Mang,
                                         const TargetMachine &TM,
@@ -33,6 +35,10 @@ public:
   MCSymbol *getCFIPersonalitySymbol(const GlobalValue *GV, Mangler &Mang,
                                     const TargetMachine &TM,
                                     MachineModuleInfo *MMI) const override;
+
+  const MCExpr *
+    getIndirectSymViaGOTPCRel(const MCSymbol *Sym, int64_t Offset,
+                              MCStreamer &Streamer) const override;
 };
 
 } // end namespace llvm