[turbofan] Allow TempReg to be SameAsFirst and FromVreg

src/compiler/instruction-selector-impl.h

Index: src/compiler/instruction-selector-impl.h
diff --git a/src/compiler/instruction-selector-impl.h b/src/compiler/instruction-selector-impl.h
index 1b1fa12e6ea2e96741b1c065268d5fa32d77aae0..1a66ea3324b3f860b4b618ec3fa67e342f896526 100644
--- a/src/compiler/instruction-selector-impl.h
+++ b/src/compiler/instruction-selector-impl.h
@@ -182,6 +182,21 @@ class OperandGenerator {
                               sequence()->NextVirtualRegister());
   }
 
+  InstructionOperand TempRegisterSameAsFirst() {
+    return UnallocatedOperand(UnallocatedOperand::SAME_AS_FIRST_INPUT,
+                              sequence()->NextVirtualRegister());
+  }
+
+  InstructionOperand TempRegisterFromVreg(int vreg) {
+    return UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
+                              UnallocatedOperand::USED_AT_START, vreg);
+  }
+
+  InstructionOperand TempRegisterFromVreg(InstructionOperand reg) {
+    return TempRegisterFromVreg(
+        UnallocatedOperand::cast(reg).virtual_register());

[Jarin, 2017/01/24 08:14:04]

I am not a big fan of taking the vreg from one operand and smashing it
elsewhere. How about exposing sequence()->NextVirtualRegister() and then have a
method that can create the operands from supplied virtual register?

I am imagining something like:

int AllocateVirtualRegister();
InstructionOperand DefineSameAsFirstForVreg(int vreg);
InstructionOperand UseRegisterForVreg(int vreg);

[john.yan, 2017/01/24 15:07:30]

That sounds better to me. Thanks.

+  }
+
   InstructionOperand TempDoubleRegister() {
     UnallocatedOperand op = UnallocatedOperand(
         UnallocatedOperand::MUST_HAVE_REGISTER,