Fix math min/max for -0.0 case. Enable min_max_test to run in optimizing compiler as well.

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 3701 matching lines @@
     summary->set_out(Location::RequiresFpuRegister());
     return summary;
   }
   ASSERT(result_cid() == kSmiCid);
   UNIMPLEMENTED();
   return NULL;
 }
 
 
 void MathMinMaxInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  ASSERT((op_kind() == MethodRecognizer::kMathMin) ||
+         (op_kind() == MethodRecognizer::kMathMax));
   if (result_cid() == kDoubleCid) {
-    Label done, is_left, is_nan;
+    Label done, returns_left, returns_nan, are_equal;
     XmmRegister left = locs()->in(0).fpu_reg();
     XmmRegister right = locs()->in(1).fpu_reg();
     XmmRegister result = locs()->out().fpu_reg();
     Register temp = locs()->temp(0).reg();
     __ comisd(left, right);
-    __ j(PARITY_EVEN, &is_nan, Assembler::kNearJump);
-    Condition double_condition;
-    if (op_kind() == MethodRecognizer::kMathMin) {
-      double_condition = TokenKindToDoubleCondition(Token::kLT);
-    } else {
-      ASSERT(op_kind() == MethodRecognizer::kMathMax);
-      double_condition = TokenKindToDoubleCondition(Token::kGT);
-    }
-    __ j(double_condition, &is_left, Assembler::kNearJump);
+    __ j(PARITY_EVEN, &returns_nan, Assembler::kNearJump);
+    __ j(EQUAL, &are_equal, Assembler::kNearJump);
+    const intptr_t is_min = (op_kind() == MethodRecognizer::kMathMin);
+    const Condition double_condition =
+        is_min ? TokenKindToDoubleCondition(Token::kLT)
+               : TokenKindToDoubleCondition(Token::kGT);
+    __ j(double_condition, &returns_left, Assembler::kNearJump);
     __ movsd(result, right);
     __ jmp(&done, Assembler::kNearJump);
-    __ Bind(&is_left);
+
+    __ Bind(&returns_left);
     __ movsd(result, left);
-    __ jmp(&done);
-    __ Bind(&is_nan);
+    __ jmp(&done, Assembler::kNearJump);
+
+    __ Bind(&returns_nan);
     static double kNaN = NAN;
     __ movq(temp, Immediate(reinterpret_cast<intptr_t>(&kNaN)));
     __ movsd(result, Address(temp, 0));
+    __ jmp(&done, Assembler::kNearJump);
+
+    __ Bind(&are_equal);
+    Label left_is_negative;
+    // Check for negative zero: -0.0 is equal 0.0 but min or max must return
+    // -0.0 or 0.0 respectively.
+    // Check for negative left value (get the sign bit):
+    // - min -> left is negative ? left : right.
+    // - max -> left is negative ? right : left
+    // Check the sign bit.
+    __ movmskpd(temp, left);
+    __ testq(temp, Immediate(1));
+    __ j(NOT_ZERO, &left_is_negative, Assembler::kNearJump);
+    // Left is positive.
+    __ movsd(result, (is_min ? right : left));
+    __ jmp(&done, Assembler::kNearJump);
+
+    __ Bind(&left_is_negative);
+    __ movsd(result, (is_min ? left : right));
     __ Bind(&done);
     return;
   }
   ASSERT(result_cid() == kSmiCid);
   UNIMPLEMENTED();
 }
 
 
 void UnarySmiOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register value = locs()->in(0).reg();
@@ skipping 715 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64