[wasm] Int64Lowering of Int64Add on ia32 and arm.

src/compiler/arm/instruction-selector-arm.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 751 matching lines @@
         Emit(kArmSbfx, g.DefineAsRegister(node),
              g.UseRegister(mleft.left().node()), g.TempImmediate(sar - shl),
              g.TempImmediate(32 - sar));
         return;
       }
     }
   }
   VisitShift(this, node, TryMatchASR);
 }
 
+void InstructionSelector::VisitInt32AddPair(Node* node) {
+  ArmOperandGenerator g(this);
+
+  InstructionOperand inputs[] = {
+      g.UseRegister(node->InputAt(0)), g.UseRegister(node->InputAt(1)),
+      g.UseRegister(node->InputAt(2)), g.UseRegister(node->InputAt(3))};
+
+  InstructionOperand outputs[] = {
+      g.DefineSameAsFirst(node),

[jbramley, 2016/03/09 10:40:17]

Is DefineSameAsFirst necessary to stop inputs 1 and 3 from being overwritten?
Otherwise, could this just be another DefineAsRegister?

[ahaas, 2016/03/09 17:28:06]

I did some experiments with the register allocation now and found out that
DefineSameAsFirst is not sufficient. The only solutions I found was using fixed
registers or a temporary register. I decided for the temporary register. Jacob,
PTAL.

+      g.DefineAsRegister(NodeProperties::FindProjection(node, 1))};
+
+  Emit(kArmAddPair, 2, outputs, 4, inputs);
+}
+
 void InstructionSelector::VisitWord32PairShl(Node* node) {
   ArmOperandGenerator g(this);
   Int32Matcher m(node->InputAt(2));
   InstructionOperand shift_operand;
   if (m.HasValue()) {
     shift_operand = g.UseImmediate(m.node());
   } else {
     shift_operand = g.UseUniqueRegister(m.node());
   }
 
@@ skipping 951 matching lines @@
              MachineOperatorBuilder::kFloat64RoundTiesAway |
              MachineOperatorBuilder::kFloat32RoundTiesEven |
              MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8