Add WoA object file emission support

Introduce support for WoA PE/COFF object file emission from LLVM.  Add the new
target specific PE/COFF Streamer (ARMWinCOFFStreamer) that handles the ARM
specific behaviour of PE/COFF object emission.  ARM exception information is not
yet emitted and is a TODO item.

The ARM specific object writer (ARMWinCOFFObjectWriter) handles the ARM specific
relocation handling in conjunction with the WinCOFFObjectWriter in the MC layer.
The MC layer needs to be updated to deal with the relocation adjustments.
Branch relocations are adjusted by 4 bytes (unlikely their ELF counterparts).

Minor tweaks to switch multiple conditional checks into equivalent switch
statements.  The ObjectFileInfo is updated to relax the object file setup for
Windows COFF.  Move the architecture checks into an assertion.  Windows COFF is
currently only supported on x86, x86_64, and ARM (thumb).  Rather than
defaulting to ELF, we will refuse to generate an object file.  This is better
though as you do not get an (arbitrary) object file which is different from the
request.

llvm-svn: 207345

1 files changed, 20 insertions, 10 deletions

diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
index c16b3554e29..aade4328db3 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
@@ -737,6 +737,15 @@ void ARMAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
 }
 
 namespace {
+// FIXME: This should be in a separate file.
+class ARMWinCOFFAsmBackend : public ARMAsmBackend {
+public:
+  ARMWinCOFFAsmBackend(const Target &T, const StringRef &Triple)
+    : ARMAsmBackend(T, Triple, true) { }
+  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+    return createARMWinCOFFObjectWriter(OS, /*Is64Bit=*/false);
+  }
+};
 
 // FIXME: This should be in a separate file.
 // ELF is an ELF of course...
@@ -777,7 +786,9 @@ MCAsmBackend *llvm::createARMAsmBackend(const Target &T,
                                         bool isLittle) {
   Triple TheTriple(TT);
 
-  if (TheTriple.isOSBinFormatMachO()) {
+  switch (TheTriple.getObjectFormat()) {
+  default: llvm_unreachable("unsupported object format");
+  case Triple::MachO: {
     MachO::CPUSubTypeARM CS =
       StringSwitch<MachO::CPUSubTypeARM>(TheTriple.getArchName())
       .Cases("armv4t", "thumbv4t", MachO::CPU_SUBTYPE_ARM_V4T)
@@ -792,15 +803,14 @@ MCAsmBackend *llvm::createARMAsmBackend(const Target &T,
 
     return new DarwinARMAsmBackend(T, TT, CS);
   }
-
-#if 0
-  // FIXME: Introduce yet another checker but assert(0).
-  if (TheTriple.isOSBinFormatCOFF())
-    assert(0 && "Windows not supported on ARM");
-#endif
-
-  uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(Triple(TT).getOS());
-  return new ELFARMAsmBackend(T, TT, OSABI, isLittle);
+  case Triple::COFF:
+    assert(TheTriple.isOSWindows() && "non-Windows ARM COFF is not supported");
+    return new ARMWinCOFFAsmBackend(T, TT);
+  case Triple::ELF:
+    assert(TheTriple.isOSBinFormatELF() && "using ELF for non-ELF target");
+    uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(Triple(TT).getOS());
+    return new ELFARMAsmBackend(T, TT, OSABI, isLittle);
+  }
 }
 
 MCAsmBackend *llvm::createARMLEAsmBackend(const Target &T,