4 files changed, 51 insertions, 1 deletions
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index 6add1b4abaa..07a9553ff1d 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -134,6 +134,9 @@ public:
                                     unsigned ValueSize = 1,
                                     unsigned MaxBytesToEmit = 0);
 
+  virtual void EmitCodeAlignment(unsigned ByteAlignment,
+                                 unsigned MaxBytesToEmit = 0);
+
   virtual void EmitValueToOffset(const MCExpr *Offset,
                                  unsigned char Value = 0);
 
@@ -513,6 +516,12 @@ void MCAsmStreamer::EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
   EmitEOL();
 }
 
+void MCAsmStreamer::EmitCodeAlignment(unsigned ByteAlignment,
+                                      unsigned MaxBytesToEmit) {
+  // FIXME: a hack for now to only work for x86 using the 0x90 nop opcode.
+  EmitValueToAlignment(ByteAlignment, 0x90, 1, MaxBytesToEmit);
+}
+
 void MCAsmStreamer::EmitValueToOffset(const MCExpr *Offset,
                                       unsigned char Value) {
   // FIXME: Verify that Offset is associated with the current section.
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 528c5c025d5..2c698e76f92 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -42,6 +42,8 @@ STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
 static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
                           MachObjectWriter &MOW);
 
+static uint64_t WriteNopData(uint64_t Count, MachObjectWriter &MOW);
+
 /// isVirtualSection - Check if this is a section which does not actually exist
 /// in the object file.
 static bool isVirtualSection(const MCSection &Section) {
@@ -1058,6 +1060,19 @@ void MCAssembler::LayoutSection(MCSectionData &SD) {
     SD.setFileSize(Address - SD.getAddress());
 }
 
+/// WriteNopData - Write optimal nops to the output file for the \arg Count
+/// bytes.  This returns the number of bytes written.  It may return 0 if
+/// the \arg Count is more than the maximum optimal nops.
+///
+/// FIXME this is X86 32-bit specific and should move to a better place.
+static uint64_t WriteNopData(uint64_t Count, MachObjectWriter &MOW) {
+  // FIXME for now just use the 0x90 nop opcode byte.
+  for (uint64_t i = 0; i < Count; i++)
+    MOW.Write8 (uint8_t(0x90));
+
+  return Count;
+}
+
 /// WriteFileData - Write the \arg F data to the output file.
 static void WriteFileData(raw_ostream &OS, const MCFragment &F,
                           MachObjectWriter &MOW) {
@@ -1081,6 +1096,14 @@ static void WriteFileData(raw_ostream &OS, const MCFragment &F,
                         "' is not a divisor of padding size '" +
                         Twine(AF.getFileSize()) + "'");
 
+    // See if we are aligning with nops, and if so do that first to try to fill
+    // the Count bytes.  Then if that did not fill any bytes or there are any
+    // bytes left to fill use the the Value and ValueSize to fill the rest.
+    if (AF.getEmitNops()) {
+      uint64_t NopByteCount = WriteNopData(Count, MOW);
+      Count -= NopByteCount;
+    }
+
     for (uint64_t i = 0; i != Count; ++i) {
       switch (AF.getValueSize()) {
       default:
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index 797be86caf2..a7a8a5daed9 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -137,6 +137,8 @@ public:
   virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
                                     unsigned ValueSize = 1,
                                     unsigned MaxBytesToEmit = 0);
+  virtual void EmitCodeAlignment(unsigned ByteAlignment,
+                                 unsigned MaxBytesToEmit = 0);
   virtual void EmitValueToOffset(const MCExpr *Offset,
                                  unsigned char Value = 0);
   
@@ -357,7 +359,20 @@ void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
   if (MaxBytesToEmit == 0)
     MaxBytesToEmit = ByteAlignment;
   new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
-                      CurSectionData);
+                      false /* EmitNops */, CurSectionData);
+
+  // Update the maximum alignment on the current section if necessary.
+  if (ByteAlignment > CurSectionData->getAlignment())
+    CurSectionData->setAlignment(ByteAlignment);
+}
+
+void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
+                                        unsigned MaxBytesToEmit) {
+  if (MaxBytesToEmit == 0)
+    MaxBytesToEmit = ByteAlignment;
+  // FIXME the 0x90 is the default x86 1 byte nop opcode.
+  new MCAlignFragment(ByteAlignment, 0x90, 1, MaxBytesToEmit,
+                      true /* EmitNops */, CurSectionData);
 
   // Update the maximum alignment on the current section if necessary.
   if (ByteAlignment > CurSectionData->getAlignment())
diff --git a/llvm/lib/MC/MCNullStreamer.cpp b/llvm/lib/MC/MCNullStreamer.cpp
index 46e9ebfa886..ab6179907e8 100644
--- a/llvm/lib/MC/MCNullStreamer.cpp
+++ b/llvm/lib/MC/MCNullStreamer.cpp
@@ -55,6 +55,9 @@ namespace {
                                       unsigned ValueSize = 1,
                                       unsigned MaxBytesToEmit = 0) {}
 
+    virtual void EmitCodeAlignment(unsigned ByteAlignment,
+                                   unsigned MaxBytesToEmit = 0) {}
+
     virtual void EmitValueToOffset(const MCExpr *Offset,
                                    unsigned char Value = 0) {}