Subzero: Add sandboxing for x86-32.

src/assembler_ia32.h

 //===- subzero/src/assembler_ia32.h - Assembler for x86-32 ------*- C++ -*-===//
 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Modified by the Subzero authors.
 //
 //===----------------------------------------------------------------------===//
 //
 //                        The Subzero Code Generator
@@ skipping 307 matching lines @@
   void NearLinkTo(intptr_t position) {
     assert(!IsBound());
     assert(num_unresolved_ < kMaxUnresolvedBranches);
     unresolved_near_positions_[num_unresolved_++] = position;
   }
 
   static const int kMaxUnresolvedBranches = 20;
 
   intptr_t position_;
   intptr_t num_unresolved_;
+  // TODO(stichnot,jvoung): Can this instead be
+  // llvm::SmallVector<intptr_t, kMaxUnresolvedBranches> ?
   intptr_t unresolved_near_positions_[kMaxUnresolvedBranches];
 
   friend class AssemblerX86;
 };
 
 class AssemblerX86 : public Assembler {
   AssemblerX86(const AssemblerX86 &) = delete;
   AssemblerX86 &operator=(const AssemblerX86 &) = delete;
 
 public:
   explicit AssemblerX86(bool use_far_branches = false) : Assembler() {
     // This mode is only needed and implemented for MIPS and ARM.
     assert(!use_far_branches);
     (void)use_far_branches;
   }
   ~AssemblerX86() override;
 
   static const bool kNearJump = true;
   static const bool kFarJump = false;
 
   void alignFunction() override;
 
   SizeT getBundleAlignLog2Bytes() const override { return 5; }
 
   llvm::ArrayRef<uint8_t> getNonExecBundlePadding() const override {
     static const uint8_t Padding[] = {0xF4};
     return llvm::ArrayRef<uint8_t>(Padding, 1);
   }
 
+  void padWithNop(intptr_t Padding) override {
+    while (Padding > MAX_NOP_SIZE) {
+      nop(MAX_NOP_SIZE);
+      Padding -= MAX_NOP_SIZE;
+    }
+    if (Padding)
+      nop(Padding);
+  }
+
   Label *GetOrCreateCfgNodeLabel(SizeT NodeNumber);
   void BindCfgNodeLabel(SizeT NodeNumber) override;
   Label *GetOrCreateLocalLabel(SizeT Number);
   void BindLocalLabel(SizeT Number);
 
   bool fixupIsPCRel(FixupKind Kind) const override {
     // Currently assuming this is the only PC-rel relocation type used.
     return Kind == llvm::ELF::R_386_PC32;
   }
 
@@ skipping 499 matching lines @@
 inline void AssemblerX86::EmitFixup(AssemblerFixup *fixup) {
   buffer_.EmitFixup(fixup);
 }
 
 inline void AssemblerX86::EmitOperandSizeOverride() { EmitUint8(0x66); }
 
 } // end of namespace x86
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ASSEMBLER_IA32_H_