[PATCH] WinCOFF: Transform IR expressions featuring __ImageBase into image relative relocations

[David Majnemer]

Hi nicholas, rafael, grosbach, rnk,

MSVC on x64 requires that we create image relative symbol
references to refer to RTTI data.  Seeing as how there is no way to
explicitly make reference to a given relocation type in LLVM IR, pattern
match expressions of the form &foo - &__ImageBase.

http://llvm-reviews.chandlerc.com/D2523

Files:
  include/llvm/IR/Operator.h
  include/llvm/Target/TargetLoweringObjectFile.h
  lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  lib/Target/X86/X86ISelLowering.cpp
  lib/Target/X86/X86TargetObjectFile.cpp
  lib/Target/X86/X86TargetObjectFile.h
  test/MC/COFF/ir-to-imgrel.ll

Index: include/llvm/IR/Operator.h
===================================================================
--- include/llvm/IR/Operator.h
+++ include/llvm/IR/Operator.h
@@ -473,6 +473,36 @@
 
 };
 
+class PtrToIntOperator
+    : public ConcreteOperator<Operator, Instruction::PtrToInt> {
+  friend class PtrToInt;
+  friend class ConstantExpr;
+
+public:
+  Value *getPointerOperand() {
+    return getOperand(0);
+  }
+  const Value *getPointerOperand() const {
+    return getOperand(0);
+  }
+  static unsigned getPointerOperandIndex() {
+    return 0U;                      // get index for modifying correct operand
+  }
+
+  /// getPointerOperandType - Method to return the pointer operand as a
+  /// PointerType.
+  Type *getPointerOperandType() const {
+    return getPointerOperand()->getType();
+  }
+
+  /// getPointerAddressSpace - Method to return the address space of the
+  /// pointer operand.
+  unsigned getPointerAddressSpace() const {
+    return cast<PointerType>(getPointerOperandType())->getAddressSpace();
+  }
+};
+
+
 } // End llvm namespace
 
 #endif
Index: include/llvm/Target/TargetLoweringObjectFile.h
===================================================================
--- include/llvm/Target/TargetLoweringObjectFile.h
+++ include/llvm/Target/TargetLoweringObjectFile.h
@@ -30,6 +30,7 @@
   class MCSymbolRefExpr;
   class MCStreamer;
   class GlobalValue;
+  class ConstantExpr;
   class TargetMachine;
   
 class TargetLoweringObjectFile : public MCObjectFileInfo {
@@ -152,6 +153,11 @@
   /// emitting the address in debug info.
   virtual const MCExpr *getDebugThreadLocalSymbol(const MCSymbol *Sym) const;
 
+  virtual const MCExpr *
+  getExecutableRelativeSymbol(const ConstantExpr *CE, Mangler *Mang) const {
+    return 0;
+  }
+
 protected:
   virtual const MCSection *
   SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1514,6 +1514,10 @@
     llvm_unreachable("Unknown constant value to lower!");
   }
 
+  if (const MCExpr *RelocExpr =
+          AP.getObjFileLowering().getExecutableRelativeSymbol(CE, AP.Mang))
+    return RelocExpr;
+
   switch (CE->getOpcode()) {
   default:
     // If the code isn't optimized, there may be outstanding folding
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -189,6 +189,8 @@
     return new X86LinuxTargetObjectFile();
   if (Subtarget->isTargetELF())
     return new TargetLoweringObjectFileELF();
+  if (Subtarget->isTargetWin64())
+    return new X86_64WindowsTargetObjectFile();
   if (Subtarget->isTargetCOFF())
     return new TargetLoweringObjectFileCOFF();
   llvm_unreachable("unknown subtarget type");
Index: lib/Target/X86/X86TargetObjectFile.cpp
===================================================================
--- lib/Target/X86/X86TargetObjectFile.cpp
+++ lib/Target/X86/X86TargetObjectFile.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "X86TargetObjectFile.h"
+#include "llvm/IR/Operator.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCSectionELF.h"
@@ -53,3 +54,26 @@
     const MCSymbol *Sym) const {
   return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
 }
+
+const MCExpr *X86_64WindowsTargetObjectFile::getExecutableRelativeSymbol(
+    const ConstantExpr *CE, Mangler *Mang) const {
+  if (const SubOperator *Sub = dyn_cast<SubOperator>(CE))
+    if (const PtrToIntOperator *SubLHS =
+            dyn_cast<PtrToIntOperator>(Sub->getOperand(0)))
+      if (const PtrToIntOperator *SubRHS =
+              dyn_cast<PtrToIntOperator>(Sub->getOperand(1)))
+        if (SubLHS->getPointerAddressSpace() == 0 &&
+            SubRHS->getPointerAddressSpace() == 0)
+          if (const GlobalVariable *GVLHS =
+                  dyn_cast<GlobalVariable>(SubLHS->getPointerOperand()))
+            if (const GlobalVariable *GVRHS =
+                    dyn_cast<GlobalVariable>(SubRHS->getPointerOperand()))
+              if (!GVLHS->isThreadLocal() && !GVRHS->isThreadLocal() &&
+                  !GVRHS->hasSection() && GVRHS->hasExternalLinkage() &&
+                  GVRHS->hasName() && GVRHS->getName() == "__ImageBase") {
+                return MCSymbolRefExpr::Create(
+                    getSymbol(*Mang, GVLHS), MCSymbolRefExpr::VK_COFF_IMGREL32,
+                    getContext());
+              }
+  return 0;
+}
Index: lib/Target/X86/X86TargetObjectFile.h
===================================================================
--- lib/Target/X86/X86TargetObjectFile.h
+++ lib/Target/X86/X86TargetObjectFile.h
@@ -41,6 +41,12 @@
     virtual const MCExpr *getDebugThreadLocalSymbol(const MCSymbol *Sym) const;
   };
 
+  /// \brief This implementation is used for Windows targets on x86-64.
+  class X86_64WindowsTargetObjectFile : public TargetLoweringObjectFileCOFF {
+    virtual const MCExpr *
+    getExecutableRelativeSymbol(const ConstantExpr *CE, Mangler *Mang) const;
+  };
+
 } // end namespace llvm
 
 #endif
Index: test/MC/COFF/ir-to-imgrel.ll
===================================================================
--- /dev/null
+++ test/MC/COFF/ir-to-imgrel.ll
@@ -0,0 +1,6 @@
+; RUN: llc -mtriple=x86_64-pc-win32 %s   -o - | FileCheck %s --check-prefix=X64
+
+ at __ImageBase = external global i8
+
+; X64: .quad   "?x@@3HA"@IMGREL32
+@"\01?x@@3HA" = global i64 sub nsw (i64 ptrtoint (i64* @"\01?x@@3HA" to i64), i64 ptrtoint (i8* @__ImageBase to i64)), align 8
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