[PATCH] D47783: [MS][ARM64]: Add AArch64_WindowsTargetObjectFile and implement AArch64_WindowsTargetObjectFile::lowerRelativeReference

[Chris January via Phabricator via llvm-commits]

arm-chrjan01 created this revision.
arm-chrjan01 added reviewers: zturner, t.p.northover, rnk.
Herald added a reviewer: javed.absar.
Herald added subscribers: llvm-commits, chrib.

Add AArch64_WindowsTargetObjectFile and implement AArch64_WindowsTargetObjectFile::lowerRelativeReference.
Fixes __ImageBase can not be defined in subtraction expression internal error.


Repository:
  rL LLVM

https://reviews.llvm.org/D47783

Files:
  lib/Target/AArch64/AArch64TargetMachine.cpp
  lib/Target/AArch64/AArch64TargetObjectFile.cpp
  lib/Target/AArch64/AArch64TargetObjectFile.h


Index: lib/Target/AArch64/AArch64TargetObjectFile.h
===================================================================
--- lib/Target/AArch64/AArch64TargetObjectFile.h
+++ lib/Target/AArch64/AArch64TargetObjectFile.h
@@ -48,6 +48,14 @@
 /// This implementation is used for AArch64 COFF targets.
 class AArch64_COFFTargetObjectFile : public TargetLoweringObjectFileCOFF {};
 
+/// This implementation is used for Windows targets on aarch64.
+class AArch64_WindowsTargetObjectFile : public AArch64_COFFTargetObjectFile {
+public:
+    const MCExpr *
+    lowerRelativeReference(const GlobalValue *LHS, const GlobalValue *RHS,
+                           const TargetMachine &TM) const override;
+};
+
 } // end namespace llvm
 
 #endif
Index: lib/Target/AArch64/AArch64TargetObjectFile.cpp
===================================================================
--- lib/Target/AArch64/AArch64TargetObjectFile.cpp
+++ lib/Target/AArch64/AArch64TargetObjectFile.cpp
@@ -78,3 +78,30 @@
   // be accessed via at least a linker-private symbol.
   getMangler().getNameWithPrefix(OutName, GV, /* CannotUsePrivateLabel */ true);
 }
+
+const MCExpr *AArch64_WindowsTargetObjectFile::lowerRelativeReference(
+    const GlobalValue *LHS, const GlobalValue *RHS,
+    const TargetMachine &TM) const {
+  // Our symbols should exist in address space zero, cowardly no-op if
+  // otherwise.
+  if (LHS->getType()->getPointerAddressSpace() != 0 ||
+      RHS->getType()->getPointerAddressSpace() != 0)
+    return nullptr;
+
+  // Both ptrtoint instructions must wrap global objects:
+  // - Only global variables are eligible for image relative relocations.
+  // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
+  // We expect __ImageBase to be a global variable without a section, externally
+  // defined.
+  //
+  // It should look something like this: @__ImageBase = external constant i8
+  if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
+      LHS->isThreadLocal() || RHS->isThreadLocal() ||
+      RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
+      cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
+    return nullptr;
+
+  return MCSymbolRefExpr::create(TM.getSymbol(LHS),
+                                 MCSymbolRefExpr::VK_COFF_IMGREL32,
+                                 getContext());
+}
Index: lib/Target/AArch64/AArch64TargetMachine.cpp
===================================================================
--- lib/Target/AArch64/AArch64TargetMachine.cpp
+++ lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -172,6 +172,8 @@
 static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
   if (TT.isOSBinFormatMachO())
     return llvm::make_unique<AArch64_MachoTargetObjectFile>();
+  if (TT.isKnownWindowsMSVCEnvironment() || TT.isWindowsCoreCLREnvironment())
+    return llvm::make_unique<AArch64_WindowsTargetObjectFile>();
   if (TT.isOSBinFormatCOFF())
     return llvm::make_unique<AArch64_COFFTargetObjectFile>();
 


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