Let target asm backends see assembler flags as they go by. Use that to handle

thumb vs. arm mode differences in WriteNopData().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121219 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 36 insertions, 5 deletions

diff --git a/include/llvm/Target/TargetAsmBackend.h b/include/llvm/Target/TargetAsmBackend.h
index ba34472690..4805e1966f 100644
--- a/include/llvm/Target/TargetAsmBackend.h
+++ b/include/llvm/Target/TargetAsmBackend.h
@@ -10,6 +10,7 @@
 #ifndef LLVM_TARGET_TARGETASMBACKEND_H
 #define LLVM_TARGET_TARGETASMBACKEND_H
 
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/Support/DataTypes.h"
 
 namespace llvm {
@@ -109,6 +110,10 @@ public:
   ///
   /// \return - True on success.
   virtual bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const = 0;
+
+  /// HandleAssemblerFlag - Handle any target-specific assembler flags.
+  /// By default, do nothing.
+  virtual void HandleAssemblerFlag(MCAssemblerFlag Flag) {}
 };
 
 } // End llvm namespace
diff --git a/lib/MC/MCMachOStreamer.cpp b/lib/MC/MCMachOStreamer.cpp
index 6f36001037..47060234b3 100644
--- a/lib/MC/MCMachOStreamer.cpp
+++ b/lib/MC/MCMachOStreamer.cpp
@@ -124,6 +124,9 @@ void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
 }
 
 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
+  // Let the target do whatever target specific stuff it needs to do.
+  getAssembler().getBackend().HandleAssemblerFlag(Flag);
+  // Do any generic stuff we need to do.
   switch (Flag) {
   case MCAF_SyntaxUnified: return; // no-op here.
   case MCAF_Code16: return; // no-op here.
diff --git a/lib/Target/ARM/ARMAsmBackend.cpp b/lib/Target/ARM/ARMAsmBackend.cpp
index 0bf6dd6e13..90b181e2cb 100644
--- a/lib/Target/ARM/ARMAsmBackend.cpp
+++ b/lib/Target/ARM/ARMAsmBackend.cpp
@@ -12,6 +12,7 @@
 #include "ARMFixupKinds.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCObjectFormat.h"
 #include "llvm/MC/MCObjectWriter.h"
@@ -27,6 +28,7 @@ using namespace llvm;
 
 namespace {
 class ARMAsmBackend : public TargetAsmBackend {
+  bool isThumbMode;  // Currently emitting Thumb code.
 public:
   ARMAsmBackend(const Target &T) : TargetAsmBackend() {}
 
@@ -36,9 +38,21 @@ public:
 
   bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const;
 
-  unsigned getPointerSize() const {
-    return 4;
+  void HandleAssemblerFlag(MCAssemblerFlag Flag) {
+    switch (Flag) {
+    default: break;
+    case MCAF_Code16:
+      setIsThumb(true);
+      break;
+    case MCAF_Code32:
+      setIsThumb(false);
+      break;
+    }
   }
+
+  unsigned getPointerSize() const { return 4; }
+  bool isThumb() const { return isThumbMode; }
+  void setIsThumb(bool it) { isThumbMode = it; }
 };
 } // end anonymous namespace
 
@@ -53,10 +67,19 @@ void ARMAsmBackend::RelaxInstruction(const MCInst &Inst, MCInst &Res) const {
 }
 
 bool ARMAsmBackend::WriteNopData(uint64_t Count, MCObjectWriter *OW) const {
-  // FIXME: Zero fill for now. That's not right, but at least will get the
-  // section size right.
+  if (isThumb()) {
+    assert (((Count & 1) == 0) && "Unaligned Nop data fragment!");
+    // FIXME: 0xbf00 is the ARMv7 value. For v6 and before, we'll need to
+    // use 0x46c0 (which is a 'mov r8, r8' insn).
+    Count /= 2;
+    for (uint64_t i = 0; i != Count; ++i)
+      OW->Write16(0xbf00);
+    return true;
+  }
+  // ARM mode
+  Count /= 4;
   for (uint64_t i = 0; i != Count; ++i)
-    OW->Write8(0);
+    OW->Write32(0xe1a00000);
   return true;
 }