5 files changed, 67 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
index da4c458ad62..dfeca1bf2f3 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
@@ -246,6 +246,12 @@ void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
   case MCCFIInstruction::OpSameValue:
     OutStreamer->EmitCFISameValue(Inst.getRegister());
     break;
+  case MCCFIInstruction::OpGnuArgsSize:
+    OutStreamer->EmitCFIGnuArgsSize(Inst.getOffset());
+    break;
+  case MCCFIInstruction::OpEscape:
+    OutStreamer->EmitCFIEscape(Inst.getValues());
+    break;
   }
 }
 
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index f9dbd5ad3f0..a6c4e282a2d 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/FormattedStream.h"
+#include "llvm/Support/LEB128.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Path.h"
 #include <cctype>
@@ -210,6 +211,8 @@ public:
   void EmitCFISameValue(int64_t Register) override;
   void EmitCFIRelOffset(int64_t Register, int64_t Offset) override;
   void EmitCFIAdjustCfaOffset(int64_t Adjustment) override;
+  void EmitCFIEscape(StringRef Values) override;
+  void EmitCFIGnuArgsSize(int64_t Size) override;
   void EmitCFISignalFrame() override;
   void EmitCFIUndefined(int64_t Register) override;
   void EmitCFIRegister(int64_t Register1, int64_t Register2) override;
@@ -1010,6 +1013,32 @@ void MCAsmStreamer::EmitCFIDefCfaOffset(int64_t Offset) {
   EmitEOL();
 }
 
+static void PrintCFIEscape(llvm::formatted_raw_ostream &OS, StringRef Values) {
+  OS << "\t.cfi_escape ";
+  if (!Values.empty()) {
+    size_t e = Values.size() - 1;
+    for (size_t i = 0; i < e; ++i)
+      OS << format("0x%02x", uint8_t(Values[i])) << ", ";
+    OS << format("0x%02x", uint8_t(Values[e]));
+  }
+}
+
+void MCAsmStreamer::EmitCFIEscape(StringRef Values) {
+  MCStreamer::EmitCFIEscape(Values);
+  PrintCFIEscape(OS, Values);
+  EmitEOL();
+}
+
+void MCAsmStreamer::EmitCFIGnuArgsSize(int64_t Size) {
+  MCStreamer::EmitCFIGnuArgsSize(Size);
+  
+  uint8_t Buffer[16] = { dwarf::DW_CFA_GNU_args_size };
+  unsigned Len = encodeULEB128(Size, Buffer + 1) + 1;
+  
+  PrintCFIEscape(OS, StringRef((const char *)&Buffer[0], Len));
+  EmitEOL();
+}
+
 void MCAsmStreamer::EmitCFIDefCfaRegister(int64_t Register) {
   MCStreamer::EmitCFIDefCfaRegister(Register);
   OS << "\t.cfi_def_cfa_register ";
diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index 58cf652b68f..e964032b9d2 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -1147,6 +1147,11 @@ void FrameEmitterImpl::EmitCFIInstruction(MCObjectStreamer &Streamer,
     Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
     return;
   }
+  case MCCFIInstruction::OpGnuArgsSize: {
+    Streamer.EmitIntValue(dwarf::DW_CFA_GNU_args_size, 1);
+    Streamer.EmitULEB128IntValue(Instr.getOffset());
+    return;
+  }
   case MCCFIInstruction::OpEscape:
     Streamer.EmitBytes(Instr.getValues());
     return;
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index 5d7685177b2..1ae1d51f2a3 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -359,6 +359,14 @@ void MCStreamer::EmitCFIEscape(StringRef Values) {
   CurFrame->Instructions.push_back(Instruction);
 }
 
+void MCStreamer::EmitCFIGnuArgsSize(int64_t Size) {
+  MCSymbol *Label = EmitCFICommon();
+  MCCFIInstruction Instruction = 
+    MCCFIInstruction::createGnuArgsSize(Label, Size);
+  MCDwarfFrameInfo *CurFrame = getCurrentDwarfFrameInfo();
+  CurFrame->Instructions.push_back(Instruction);
+}
+
 void MCStreamer::EmitCFISignalFrame() {
   EnsureValidDwarfFrame();
   MCDwarfFrameInfo *CurFrame = getCurrentDwarfFrameInfo();
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 1895cd87b10..fc314d76c64 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -2073,8 +2073,6 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
     // If the stack pointer can be changed after prologue, turn the
     // adjcallstackup instruction into a 'sub ESP, <amt>' and the
     // adjcallstackdown instruction into 'add ESP, <amt>'
-    if (Amount == 0)
-      return;
 
     // We need to keep the stack aligned properly.  To do this, we round the
     // amount of space needed for the outgoing arguments up to the next
@@ -2082,6 +2080,25 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
     unsigned StackAlign = getStackAlignment();
     Amount = RoundUpToAlignment(Amount, StackAlign);
 
+    // If we have any exception handlers in this function, and we adjust
+    // the SP before calls, we may need to indicate this to the unwinder,
+    // using GNU_ARGS_SIZE. Note that this may be necessary
+    // even when Amount == 0, because the preceding function may have
+    // set a non-0 GNU_ARGS_SIZE.
+    // TODO: We don't need to reset this between subsequent functions,
+    // if it didn't change.
+    bool HasDwarfEHHandlers =
+      !MF.getTarget().getMCAsmInfo()->usesWindowsCFI() &&
+      !MF.getMMI().getLandingPads().empty();
+
+    if (HasDwarfEHHandlers && !isDestroy && 
+        MF.getInfo<X86MachineFunctionInfo>()->getHasPushSequences())
+      BuildCFI(MBB, I, DL,
+               MCCFIInstruction::createGnuArgsSize(nullptr, Amount));
+
+    if (Amount == 0)
+      return;
+
     // Factor out the amount that gets handled inside the sequence
     // (Pushes of argument for frame setup, callee pops for frame destroy)
     Amount -= InternalAmt;