Uses an object pool on x64

runtime/vm/instructions_x64.cc

Index: runtime/vm/instructions_x64.cc
===================================================================
--- runtime/vm/instructions_x64.cc	(revision 27291)
+++ runtime/vm/instructions_x64.cc	(working copy)
@@ -11,6 +11,13 @@
 
 namespace dart {
 
+intptr_t InstructionPattern::IndexFromPPLoad(uword start) {
+  int32_t offset = *reinterpret_cast<int32_t*>(start);
+  offset +=  kHeapObjectTag;
+  return (offset - Array::data_offset()) / kWordSize;
+}
+
+
 bool InstructionPattern::TestBytesWith(const int* data, int num_bytes) const {
   ASSERT(data != NULL);
   const uint8_t* byte_array = reinterpret_cast<const uint8_t*>(start_);
@@ -24,13 +31,13 @@
 }
 
 
-uword CallOrJumpPattern::TargetAddress() const {
+uword CallPattern::TargetAddress() const {
   ASSERT(IsValid());
   return *reinterpret_cast<uword*>(start() + 2);
 }
 
 
-void CallOrJumpPattern::SetTargetAddress(uword target) const {
+void CallPattern::SetTargetAddress(uword target) const {
   ASSERT(IsValid());
   *reinterpret_cast<uword*>(start() + 2) = target;
   CPU::FlushICache(start() + 2, kWordSize);
@@ -46,11 +53,27 @@
 }
 
 
+uword JumpPattern::TargetAddress() const {
+  ASSERT(IsValid());
+  int index = InstructionPattern::IndexFromPPLoad(start() + 3);
+  return reinterpret_cast<uword>(object_pool_.At(index));
+}
+
+
+void JumpPattern::SetTargetAddress(uword target) const {
+  ASSERT(IsValid());
+  int index = InstructionPattern::IndexFromPPLoad(start() + 3);
+  const Smi& smi = Smi::Handle(reinterpret_cast<RawSmi*>(target));
+  object_pool_.SetAt(index, smi);
+  // No need to flush the instruction cache, since the code is not modified.
+}
+
+
 const int* JumpPattern::pattern() const {
-  // movq $target, TMP
-  // jmpq TMP
+  //  00: 4d 8b 9d imm32  mov R11, [R13 + off]
+  //  07: 41 ff e3        jmpq R11
   static const int kJumpPattern[kLengthInBytes] =
-      {0x49, 0xBB, -1, -1, -1, -1, -1, -1, -1, -1, 0x41, 0xFF, 0xE3};
+      {0x4D, 0x8B, -1, -1, -1, -1, -1, 0x41, 0xFF, 0xE3};
   return kJumpPattern;
 }