Remove branching and binding with two arguments from the JumpTarget...

src/ia32/codegen-ia32.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1853 matching lines @@
         Result temp = left_side;
         left_side = right_side;
         right_side = temp;
         cc = ReverseCondition(cc);
         // This may reintroduce greater or less_equal as the value of cc.
         // CompareStub and the inline code both support all values of cc.
       }
       // Implement comparison against a constant Smi, inlining the case
       // where both sides are Smis.
       left_side.ToRegister();
-      ASSERT(left_side.is_valid());
+
+      // Here we split control flow to the stub call and inlined cases
+      // before finally splitting it to the control destination.  We use
+      // a jump target and branching to duplicate the virtual frame at
+      // the first split.  We manually handle the off-frame references
+      // by reconstituting them on the non-fall-through path.
       JumpTarget is_smi;
+      Register left_reg = left_side.reg();
+      Handle<Object> right_val = right_side.handle();
       __ test(left_side.reg(), Immediate(kSmiTagMask));
-      is_smi.Branch(zero, &left_side, &right_side, taken);
+      is_smi.Branch(zero, taken);
 
-      // Setup and call the compare stub, which expects its arguments
-      // in registers.
+      // Setup and call the compare stub.
       CompareStub stub(cc, strict);
       Result result = frame_->CallStub(&stub, &left_side, &right_side);
       result.ToRegister();
       __ cmp(result.reg(), 0);
       result.Unuse();
       dest->true_target()->Branch(cc);
       dest->false_target()->Jump();
 
-      is_smi.Bind(&left_side, &right_side);
-      left_side.ToRegister();
+      is_smi.Bind();
+      left_side = Result(left_reg);
+      right_side = Result(right_val);
       // Test smi equality and comparison by signed int comparison.
       if (IsUnsafeSmi(right_side.handle())) {
         right_side.ToRegister();
-        ASSERT(right_side.is_valid());
         __ cmp(left_side.reg(), Operand(right_side.reg()));
       } else {
         __ cmp(Operand(left_side.reg()), Immediate(right_side.handle()));
       }
       left_side.Unuse();
       right_side.Unuse();
       dest->Split(cc);
     }
   } else if (cc == equal &&
              (left_side_constant_null || right_side_constant_null)) {
@@ skipping 31 matching lines @@
       operand.Unuse();
       dest->Split(not_zero);
     }
   } else {  // Neither side is a constant Smi or null.
     // If either side is a non-smi constant, skip the smi check.
     bool known_non_smi =
         (left_side.is_constant() && !left_side.handle()->IsSmi()) ||
         (right_side.is_constant() && !right_side.handle()->IsSmi());
     left_side.ToRegister();
     right_side.ToRegister();
-    JumpTarget is_smi;
-    if (!known_non_smi) {
-      // Check for the smi case.
+
+    if (known_non_smi) {
+      // When non-smi, call out to the compare stub.
+      CompareStub stub(cc, strict);
+      Result answer = frame_->CallStub(&stub, &left_side, &right_side);
+      if (cc == equal) {
+        __ test(answer.reg(), Operand(answer.reg()));
+      } else {
+        __ cmp(answer.reg(), 0);
+      }
+      answer.Unuse();
+      dest->Split(cc);
+    } else {
+      // Here we split control flow to the stub call and inlined cases
+      // before finally splitting it to the control destination.  We use
+      // a jump target and branching to duplicate the virtual frame at
+      // the first split.  We manually handle the off-frame references
+      // by reconstituting them on the non-fall-through path.
+      JumpTarget is_smi;
+      Register left_reg = left_side.reg();
+      Register right_reg = right_side.reg();
+
       Result temp = allocator_->Allocate();
       ASSERT(temp.is_valid());
       __ mov(temp.reg(), left_side.reg());
       __ or_(temp.reg(), Operand(right_side.reg()));
       __ test(temp.reg(), Immediate(kSmiTagMask));
       temp.Unuse();
-      is_smi.Branch(zero, &left_side, &right_side, taken);
-    }
-    // When non-smi, call out to the compare stub, which expects its
-    // arguments in registers.
-    CompareStub stub(cc, strict);
-    Result answer = frame_->CallStub(&stub, &left_side, &right_side);
-    if (cc == equal) {
-      __ test(answer.reg(), Operand(answer.reg()));
-    } else {
-      __ cmp(answer.reg(), 0);
-    }
-    answer.Unuse();
-    if (known_non_smi) {
-      dest->Split(cc);
-    } else {
+      is_smi.Branch(zero, taken);
+      // When non-smi, call out to the compare stub.
+      CompareStub stub(cc, strict);
+      Result answer = frame_->CallStub(&stub, &left_side, &right_side);

[William Hesse, 2009/06/12 14:05:38]

Is it worth a comment that here is where left_side and right_side are
invalidated for the first time?

+      if (cc == equal) {
+        __ test(answer.reg(), Operand(answer.reg()));
+      } else {
+        __ cmp(answer.reg(), 0);
+      }
+      answer.Unuse();
       dest->true_target()->Branch(cc);
       dest->false_target()->Jump();
-      is_smi.Bind(&left_side, &right_side);
-      left_side.ToRegister();
-      right_side.ToRegister();
+
+      is_smi.Bind();
+      left_side = Result(left_reg);
+      right_side = Result(right_reg);
       __ cmp(left_side.reg(), Operand(right_side.reg()));
       right_side.Unuse();
       left_side.Unuse();
       dest->Split(cc);
     }
   }
 }
 
 
 class CallFunctionStub: public CodeStub {
@@ skipping 5486 matching lines @@
 
   // Slow-case: Go through the JavaScript implementation.
   __ bind(&slow);
   __ InvokeBuiltin(Builtins::INSTANCE_OF, JUMP_FUNCTION);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal