X64: Make comparisons work on zero-extended smis.

src/x64/codegen-x64.cc

 // Copyright 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 2441 matching lines @@
   }
 
   // Resolve the call.
   Result result =
       frame_->CallRuntime(Runtime::kResolvePossiblyDirectEval, 2);
 
   // Touch up the stack with the right values for the function and the
   // receiver.  Use a scratch register to avoid destroying the result.
   Result scratch = allocator_->Allocate();
   ASSERT(scratch.is_valid());
-  __ movl(scratch.reg(),
+  __ movq(scratch.reg(),
           FieldOperand(result.reg(), FixedArray::OffsetOfElementAt(0)));
   frame_->SetElementAt(arg_count + 1, &scratch);
 
   // We can reuse the result register now.
   frame_->Spill(result.reg());
-  __ movl(result.reg(),
+  __ movq(result.reg(),
           FieldOperand(result.reg(), FixedArray::OffsetOfElementAt(1)));
   frame_->SetElementAt(arg_count, &result);
 
   // Call the function.
   CodeForSourcePosition(node->position());
   InLoopFlag in_loop = loop_nesting() > 0 ? IN_LOOP : NOT_IN_LOOP;
   CallFunctionStub call_function(arg_count, in_loop);
   result = frame_->CallStub(&call_function, arg_count + 1);
 
   // Restore the context and overwrite the function on the stack with
@@ skipping 1830 matching lines @@
       result.ToRegister();
       __ testq(result.reg(), result.reg());
       result.Unuse();
       dest->true_target()->Branch(cc);
       dest->false_target()->Jump();
 
       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();
-        __ cmpq(left_side.reg(), right_side.reg());
-      } else {
-        __ Cmp(left_side.reg(), right_side.handle());
-      }
+      // Both sides are smis, so we can use an Immediate.
+      __ cmpl(left_side.reg(), Immediate(Smi::cast(*right_side.handle())));
       left_side.Unuse();
       right_side.Unuse();
       dest->Split(cc);
     }
   } else if (cc == equal &&
              (left_side_constant_null || right_side_constant_null)) {
     // To make null checks efficient, we check if either the left side or
     // the right side is the constant 'null'.
     // If so, we optimize the code by inlining a null check instead of
     // calling the (very) general runtime routine for checking equality.
@@ skipping 31 matching lines @@
     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();
 
     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);
-      __ testq(answer.reg(), answer.reg());  // Both zero and sign flag right.
+      // The result is a Smi, which is negative, zero, or positive.
+      __ testl(answer.reg(), answer.reg());  // Both zero and sign flag right.
       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();
 
       __ movq(kScratchRegister, left_reg);
       __ or_(kScratchRegister, right_reg);
       __ testl(kScratchRegister, Immediate(kSmiTagMask));
       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);
-      if (cc == equal) {
-        __ testq(answer.reg(), answer.reg());
-      } else {
-        __ cmpq(answer.reg(), Immediate(0));
-      }
+      __ testl(answer.reg(), answer.reg());  // Sets both zero and sign flags.
       answer.Unuse();
       dest->true_target()->Branch(cc);
       dest->false_target()->Jump();
 
       is_smi.Bind();
       left_side = Result(left_reg);
       right_side = Result(right_reg);
-      __ cmpq(left_side.reg(), right_side.reg());
+      __ cmpl(left_side.reg(), right_side.reg());
       right_side.Unuse();
       left_side.Unuse();
       dest->Split(cc);
     }
   }
 }
 
 
 // Flag that indicates whether or not the code that handles smi arguments
 // should be placed in the stub, inlined, or omitted entirely.
@@ skipping 1020 matching lines @@
   __ and_(rcx, Immediate(kStringSizeMask));
   __ cmpq(rcx, Immediate(kShortStringTag));
   __ j(not_equal, &true_result);  // Empty string is always short.
   __ movq(rdx, FieldOperand(rax, String::kLengthOffset));
   __ shr(rdx, Immediate(String::kShortLengthShift));
   __ j(zero, &false_result);
   __ jmp(&true_result);
 
   __ bind(&not_string);
   // HeapNumber => false iff +0, -0, or NaN.
+  // These three cases set C3 when compared to zero in the FPU.
   __ Cmp(rdx, Factory::heap_number_map());
   __ j(not_equal, &true_result);
   // TODO(x64): Don't use fp stack, use MMX registers?
   __ fldz();  // Load zero onto fp stack
   // Load heap-number double value onto fp stack
   __ fld_d(FieldOperand(rax, HeapNumber::kValueOffset));
   __ fucompp();  // Compare and pop both values.
   __ movq(kScratchRegister, rax);
   __ fnstsw_ax();  // Store fp status word in ax, no checking for exceptions.
-  __ testb(rax, Immediate(0x08));  // Test FP condition flag C3.
+  __ testl(rax, Immediate(0x4000));  // Test FP condition flag C3, bit 16.
   __ movq(rax, kScratchRegister);
-  __ j(zero, &false_result);
+  __ j(not_zero, &false_result);
   // Fall through to |true_result|.
 
   // Return 1/0 for true/false in rax.
   __ bind(&true_result);
   __ movq(rax, Immediate(1));
   __ ret(1 * kPointerSize);
   __ bind(&false_result);
   __ xor_(rax, rax);
   __ ret(1 * kPointerSize);
 }
@@ skipping 149 matching lines @@
       __ movq(rbx, 0x7ff0000000000000, RelocInfo::NONE);
       __ movq(rax, FieldOperand(rdx, HeapNumber::kValueOffset));
       // Test that exponent bits are all set.
       __ or_(rbx, rax);
       __ cmpq(rbx, rax);
       __ j(not_equal, &return_equal);
       // Shift out flag and all exponent bits, retaining only mantissa.
       __ shl(rax, Immediate(12));
       // If all bits in the mantissa are zero the number is Infinity, and
       // we return zero.  Otherwise it is a NaN, and we return non-zero.
-      // So just return rax.
+      // We cannot just return rax because only eax is tested on return.
+      // TODO(X64): Solve this using movcc, when implemented.
+      __ movq(kScratchRegister, rax);
+      __ shr(kScratchRegister, Immediate(32));
+      __ or_(rax, kScratchRegister);
       __ ret(0);
 
       __ bind(&not_identical);
     }
 
     // If we're doing a strict equality comparison, we don't have to do
     // type conversion, so we generate code to do fast comparison for objects
     // and oddballs. Non-smi numbers and strings still go through the usual
     // slow-case code.
     if (strict_) {
@@ skipping 17 matching lines @@
         __ xor_(rbx, rax);
         __ and_(rbx, rcx);  // rbx holds either 0 or rax ^ rdx.
         __ xor_(rbx, rax);
         // if rax was smi, rbx is now rdx, else rax.
 
         // Check if the non-smi operand is a heap number.
         __ Cmp(FieldOperand(rbx, HeapObject::kMapOffset),
                Factory::heap_number_map());
         // If heap number, handle it in the slow case.
         __ j(equal, &slow);
-        // Return non-equal (ebx is not zero)
+        // Return non-equal.  ebx (the lower half of rbx) is not zero.
         __ movq(rax, rbx);
         __ ret(0);
 
         __ bind(&not_smis);
       }
 
       // If either operand is a JSObject or an oddball value, then they are not
       // equal since their pointers are different
       // There is no test for undetectability in strict equality.
 
       // If the first object is a JS object, we have done pointer comparison.
       ASSERT(LAST_TYPE == JS_FUNCTION_TYPE);
       Label first_non_object;
       __ CmpObjectType(rax, FIRST_JS_OBJECT_TYPE, rcx);
       __ j(below, &first_non_object);
-      // Return non-zero (rax is not zero)
+      // Return non-zero (eax (not rax) is not zero)
       Label return_not_equal;
       ASSERT(kHeapObjectTag != 0);
       __ bind(&return_not_equal);
       __ ret(0);
 
       __ bind(&first_non_object);
       // Check for oddballs: true, false, null, undefined.
       __ CmpInstanceType(rcx, ODDBALL_TYPE);
       __ j(equal, &return_not_equal);
 
@@ skipping 43 matching lines @@
   __ movq(rax, Immediate(1));
   __ ret(2 * kPointerSize);  // rax, rdx were pushed
 
   // Fast negative check for symbol-to-symbol equality.
   __ bind(&check_for_symbols);
   if (cc_ == equal) {
     BranchIfNonSymbol(masm, &call_builtin, rax, kScratchRegister);
     BranchIfNonSymbol(masm, &call_builtin, rdx, kScratchRegister);
 
     // We've already checked for object identity, so if both operands
-    // are symbols they aren't equal. Register rax already holds a
+    // are symbols they aren't equal. Register eax (not rax) already holds a
     // non-zero value, which indicates not equal, so just return.
     __ ret(2 * kPointerSize);
   }
 
   __ bind(&call_builtin);
   // must swap argument order
   __ pop(rcx);
   __ pop(rdx);
   __ pop(rax);
   __ push(rdx);
@@ skipping 1176 matching lines @@
 int CompareStub::MinorKey() {
   // Encode the two parameters in a unique 16 bit value.
   ASSERT(static_cast<unsigned>(cc_) < (1 << 15));
   return (static_cast<unsigned>(cc_) << 1) | (strict_ ? 1 : 0);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal