1 files changed, 72 insertions, 3 deletions

diff --git a/lib/Target/X86/X86AsmPrinter.h b/lib/Target/X86/X86AsmPrinter.h
index b1bbe8e41cc0..748b948d212f 100644
--- a/lib/Target/X86/X86AsmPrinter.h
+++ b/lib/Target/X86/X86AsmPrinter.h
@@ -7,14 +7,19 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef X86ASMPRINTER_H
-#define X86ASMPRINTER_H
+#ifndef LLVM_LIB_TARGET_X86_X86ASMPRINTER_H
+#define LLVM_LIB_TARGET_X86_X86ASMPRINTER_H
 
 #include "X86Subtarget.h"
 #include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/CodeGen/StackMaps.h"
 #include "llvm/Target/TargetMachine.h"
 
+// Implemented in X86MCInstLower.cpp
+namespace {
+  class X86MCInstLower;
+}
+
 namespace llvm {
 class MCStreamer;
 class MCSymbol;
@@ -25,9 +30,63 @@ class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
 
   void GenerateExportDirective(const MCSymbol *Sym, bool IsData);
 
+  // This utility class tracks the length of a stackmap instruction's 'shadow'.
+  // It is used by the X86AsmPrinter to ensure that the stackmap shadow
+  // invariants (i.e. no other stackmaps, patchpoints, or control flow within
+  // the shadow) are met, while outputting a minimal number of NOPs for padding.
+  //
+  // To minimise the number of NOPs used, the shadow tracker counts the number
+  // of instruction bytes output since the last stackmap. Only if there are too
+  // few instruction bytes to cover the shadow are NOPs used for padding.
+  class StackMapShadowTracker {
+  public:
+    StackMapShadowTracker(TargetMachine &TM);
+    ~StackMapShadowTracker();
+    void startFunction(MachineFunction &MF);
+    void count(MCInst &Inst, const MCSubtargetInfo &STI);
+
+    // Called to signal the start of a shadow of RequiredSize bytes.
+    void reset(unsigned RequiredSize) {
+      RequiredShadowSize = RequiredSize;
+      CurrentShadowSize = 0;
+      InShadow = true;
+    }
+
+    // Called before every stackmap/patchpoint, and at the end of basic blocks,
+    // to emit any necessary padding-NOPs.
+    void emitShadowPadding(MCStreamer &OutStreamer, const MCSubtargetInfo &STI);
+  private:
+    TargetMachine &TM;
+    std::unique_ptr<MCCodeEmitter> CodeEmitter;
+    bool InShadow;
+
+    // RequiredShadowSize holds the length of the shadow specified in the most
+    // recently encountered STACKMAP instruction.
+    // CurrentShadowSize counts the number of bytes encoded since the most
+    // recently encountered STACKMAP, stopping when that number is greater than
+    // or equal to RequiredShadowSize.
+    unsigned RequiredShadowSize, CurrentShadowSize;
+  };
+
+  StackMapShadowTracker SMShadowTracker;
+
+  // All instructions emitted by the X86AsmPrinter should use this helper
+  // method.
+  //
+  // This helper function invokes the SMShadowTracker on each instruction before
+  // outputting it to the OutStream. This allows the shadow tracker to minimise
+  // the number of NOPs used for stackmap padding.
+  void EmitAndCountInstruction(MCInst &Inst);
+
+  void InsertStackMapShadows(MachineFunction &MF);
+  void LowerSTACKMAP(const MachineInstr &MI);
+  void LowerPATCHPOINT(const MachineInstr &MI);
+
+  void LowerTlsAddr(X86MCInstLower &MCInstLowering, const MachineInstr &MI);
+
  public:
   explicit X86AsmPrinter(TargetMachine &TM, MCStreamer &Streamer)
-    : AsmPrinter(TM, Streamer), SM(*this) {
+    : AsmPrinter(TM, Streamer), SM(*this), SMShadowTracker(TM) {
     Subtarget = &TM.getSubtarget<X86Subtarget>();
   }
 
@@ -43,6 +102,10 @@ class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
 
   void EmitInstruction(const MachineInstr *MI) override;
 
+  void EmitBasicBlockEnd(const MachineBasicBlock &MBB) override {
+    SMShadowTracker.emitShadowPadding(OutStreamer, getSubtargetInfo());
+  }
+
   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                        unsigned AsmVariant, const char *ExtraCode,
                        raw_ostream &OS) override;
@@ -53,6 +116,12 @@ class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
   /// \brief Return the symbol for the specified constant pool entry.
   MCSymbol *GetCPISymbol(unsigned CPID) const override;
 
+  bool doInitialization(Module &M) override {
+    SMShadowTracker.reset(0);
+    SM.reset();
+    return AsmPrinter::doInitialization(M);
+  }
+
   bool runOnMachineFunction(MachineFunction &F) override;
 };