MC: Support COFF image-relative MCSymbolRefs

Add support for the COFF relocation types IMAGE_REL_I386_DIR32NB and
IMAGE_REL_AMD64_ADDR32NB for 32- and 64-bit respectively. These are
similar to normal 4-byte relocations except that they do not include
the base address of the image.

Image-relative relocations are used for debug information (32-bit) and
SEH unwind tables (64-bit).

A new MCSymbolRef variant called 'VK_COFF_IMGREL32' is introduced to
specify such relocations. For AT&T assembly, this variant can be accessed
using the symbol suffix '@imgrel'.

llvm-svn: 179240

2 files changed, 8 insertions, 2 deletions

diff --git a/llvm/include/llvm/MC/MCExpr.h b/llvm/include/llvm/MC/MCExpr.h
index b5bfed18eca..a2c5bd3f766 100644
--- a/llvm/include/llvm/MC/MCExpr.h
+++ b/llvm/include/llvm/MC/MCExpr.h
@@ -216,7 +216,9 @@ public:
     VK_Mips_GOT_HI16,
     VK_Mips_GOT_LO16,
     VK_Mips_CALL_HI16,
-    VK_Mips_CALL_LO16
+    VK_Mips_CALL_LO16,
+
+    VK_COFF_IMGREL32 // symbol@imgrel (image-relative)
   };
 
 private:
diff --git a/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h b/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h
index 11df5749d45..f13e7d54802 100644
--- a/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h
+++ b/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h
@@ -11,7 +11,9 @@
 #define LLVM_MC_MCWINCOFFOBJECTWRITER_H
 
 namespace llvm {
+  class MCFixup;
   class MCObjectWriter;
+  class MCValue;
   class raw_ostream;
 
   class MCWinCOFFObjectTargetWriter {
@@ -24,7 +26,9 @@ namespace llvm {
     virtual ~MCWinCOFFObjectTargetWriter() {}
 
     unsigned getMachine() const { return Machine; }
-    virtual unsigned getRelocType(unsigned FixupKind) const = 0;
+    virtual unsigned getRelocType(const MCValue &Target,
+                                  const MCFixup &Fixup,
+                                  bool IsCrossSection) const = 0;
   };
 
   /// \brief Construct a new Win COFF writer instance.