Implement code patcher for x64

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
===================================================================
--- src/x64/assembler-x64.cc	(revision 2868)
+++ src/x64/assembler-x64.cc	(working copy)
@@ -173,22 +173,32 @@
 // Patch the code at the current PC with a call to the target address.
 // Additional guard int3 instructions can be added if required.
 void RelocInfo::PatchCodeWithCall(Address target, int guard_bytes) {
-  // Call instruction takes up 13 bytes and int3 takes up one byte.
-  static const int kCallInstructionSize = 13;
-  Address patch_site = pc_;
-  Memory::uint16_at(patch_site) = 0xBA49u;  // movq r10, imm64
-  // Write "0x00, call r10" starting at last byte of address.  We overwrite
-  // the 0x00 later, and this lets us write a uint32.
-  Memory::uint32_at(patch_site + 9) = 0xD2FF4900u;  // 0x00, call r10
-  Memory::Address_at(patch_site + 2) = target;
+  // Load register with immediate 64 and call through a register instructions
+  // takes up 13 bytes and int3 takes up one byte.
+  static const int kCallCodeSize = 13;
+  int code_size = kCallCodeSize + guard_bytes;
 
+  // Create a code patcher.
+  CodePatcher patcher(pc_, code_size);
+
+  // Add a label for checking the size of the code used for returning.
+#ifdef DEBUG
+  Label check_codesize;
+  patcher.masm()->bind(&check_codesize);
+#endif
+
+  // Patch the code.
+  patcher.masm()->movq(r10, target, RelocInfo::NONE);
+  patcher.masm()->call(r10);
+
+  // Check that the size of the code generated is as expected.
+  ASSERT_EQ(kCallCodeSize,
+            patcher.masm()->SizeOfCodeGeneratedSince(&check_codesize));
+
   // Add the requested number of int3 instructions after the call.
   for (int i = 0; i < guard_bytes; i++) {
-    *(patch_site + kCallInstructionSize + i) = 0xCC;  // int3
+    patcher.masm()->int3();
   }
-
-  // Indicate that code has changed.
-  CPU::FlushICache(patch_site, kCallInstructionSize + guard_bytes);
 }
 
 
@@ -197,6 +207,9 @@
   for (int i = 0; i < instruction_count; i++) {
     *(pc_ + i) = *(instructions + i);
   }
+
+  // Indicate that code has changed.
+  CPU::FlushICache(pc_, instruction_count);
 }
 
 // -----------------------------------------------------------------------------