[wasm] Reuse constrained input for same vreg

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 ecda4533517e8a21fbcf7a9741f8cf443ec498d0..5a2ebc597067193db126ebd8d1a8e5f637660975 100644
--- a/src/compiler/instruction-selector-impl.h
+++ b/src/compiler/instruction-selector-impl.h
@@ -50,8 +50,13 @@ class OperandGenerator {
   }
 
   InstructionOperand DefineAsFixed(Node* node, Register reg) {
-    return Define(node, UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER,
-                                           reg.code(), GetVReg(node)));
+    UnallocatedOperand op = DefineAsFixedForVreg(GetVReg(node), reg);
+    return Define(node, op);
+  }
+
+  UnallocatedOperand DefineAsFixedForVreg(int vreg, Register reg) {
+    return UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER, reg.code(),
+                              vreg);
   }
 
   template <typename FPRegType>
@@ -188,10 +193,15 @@ class OperandGenerator {
     return UnallocatedOperand(UnallocatedOperand::SAME_AS_FIRST_INPUT, vreg);
   }
 
-  InstructionOperand DefineAsRegistertForVreg(int vreg) {
+  InstructionOperand DefineAsRegisterForVreg(int vreg) {
     return UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER, vreg);
   }
 
+  InstructionOperand UseFixedForVreg(int vreg, Register reg) {
+    return UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER, reg.code(),
+                              vreg);
+  }
+
   InstructionOperand UseRegisterForVreg(int vreg) {
     return UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
                               UnallocatedOperand::USED_AT_START, vreg);