Second attempt: Improve our type feedback by recogizining never-executed IC c...

src/ia32/ic-ia32.cc

Index: src/ia32/ic-ia32.cc
===================================================================
--- src/ia32/ic-ia32.cc	(revision 6011)
+++ src/ia32/ic-ia32.cc	(working copy)
@@ -2049,13 +2049,23 @@
 }
 
 
+static bool HasInlinedSmiCode(Address address) {
+  // The address of the instruction following the call.
+  Address test_instruction_address =
+      address + Assembler::kCallTargetAddressOffset;
+
+  // If the instruction following the call is not a test al, nothing
+  // was inlined.
+  return *test_instruction_address == Assembler::kTestAlByte;
+}
+
+
 void CompareIC::UpdateCaches(Handle<Object> x, Handle<Object> y) {
   HandleScope scope;
   Handle<Code> rewritten;
-#ifdef DEBUG
   State previous_state = GetState();
-#endif
-  State state = TargetState(x, y);
+
+  State state = TargetState(previous_state, HasInlinedSmiCode(address()), x, y);
   if (state == GENERIC) {
     CompareStub stub(GetCondition(), strict(), NO_COMPARE_FLAGS);
     rewritten = stub.GetCode();
@@ -2073,9 +2083,47 @@
            Token::Name(op_));
   }
 #endif
+
+  // Activate inlined smi code.
+  if (previous_state == UNINITIALIZED) {
+    PatchInlinedSmiCode(address());
+  }
 }
 
 
+void PatchInlinedSmiCode(Address address) {
+  // The address of the instruction following the call.
+  Address test_instruction_address =
+      address + Assembler::kCallTargetAddressOffset;
+
+  // If the instruction following the call is not a test al, nothing
+  // was inlined.
+  if (*test_instruction_address != Assembler::kTestAlByte) {
+    ASSERT(*test_instruction_address == Assembler::kNopByte);
+    return;
+  }
+
+  Address delta_address = test_instruction_address + 1;
+  // The delta to the start of the map check instruction and the
+  // condition code uses at the patched jump.
+  int8_t delta = *reinterpret_cast<int8_t*>(delta_address);
+  if (FLAG_trace_ic) {
+    PrintF("[  patching ic at %p, test=%p, delta=%d\n",
+           address, test_instruction_address, delta);
+  }
+
+  // Patch with a short conditional jump. There must be a
+  // short jump-if-carry/not-carry at this position.
+  Address jmp_address = test_instruction_address - delta;
+  ASSERT(*jmp_address == Assembler::kJncShortOpcode ||
+         *jmp_address == Assembler::kJcShortOpcode);
+  Condition cc = *jmp_address ==  Assembler::kJncShortOpcode

[Vitaly Repeshko, 2010/12/15 12:18:50]

Nit: "(*jmp_address ==  Assembler::kJncShortOpcode)".

+      ? not_zero
+      : zero;
+  *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
+}
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32