[Turbofan] Add the concept of aliasing to RegisterConfiguration.

src/compiler/arm/code-generator-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/compiler/code-generator.h"
 
 #include "src/arm/macro-assembler-arm.h"
 #include "src/ast/scopes.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
@@ skipping 17 matching lines @@
       : InstructionOperandConverter(gen, instr) {}
 
   SwVfpRegister OutputFloat32Register(size_t index = 0) {
     return ToFloat32Register(instr_->OutputAt(index));
   }
 
   SwVfpRegister InputFloat32Register(size_t index) {
     return ToFloat32Register(instr_->InputAt(index));
   }
 
   SwVfpRegister ToFloat32Register(InstructionOperand* op) {

[Mircea Trofin, 2016/06/22 06:07:34]

If this is only called for LocationOperands, should we change the signature
accordingly?

[bbudge, 2016/06/22 20:16:03]

I followed the pattern of ToFloat64Register. Changing the signature would
require casts at all the call sites (there are about 10 for both functions).

-    return ToFloat64Register(op).low();
+    DCHECK(LocationOperand::cast(op)->representation() ==
+           MachineRepresentation::kFloat32);
+    return LocationOperand::cast(op)->GetFloatRegister();
   }
 
   LowDwVfpRegister OutputFloat64Register(size_t index = 0) {
     return ToFloat64Register(instr_->OutputAt(index));
   }
 
   LowDwVfpRegister InputFloat64Register(size_t index) {
     return ToFloat64Register(instr_->InputAt(index));
   }
 
@@ skipping 1765 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8