s390: Remove RSubI on s390 and optimize ConstantI

src/crankshaft/s390/lithium-s390.cc

Index: src/crankshaft/s390/lithium-s390.cc
diff --git a/src/crankshaft/s390/lithium-s390.cc b/src/crankshaft/s390/lithium-s390.cc
index 3d1476403295ffe6d6c06d7f30e910cf81192aea..4698d33938c16f0afc25f9b9d91d41d548fd3259 100644
--- a/src/crankshaft/s390/lithium-s390.cc
+++ b/src/crankshaft/s390/lithium-s390.cc
@@ -20,6 +20,18 @@ namespace internal {
 LITHIUM_CONCRETE_INSTRUCTION_LIST(DEFINE_COMPILE)
 #undef DEFINE_COMPILE
 
+const char* LInstruction::GetOpcodeName(LInstruction::Opcode op) {
+  switch (op) {

[JoranSiu, 2016/12/07 21:01:42]

What is the purpose of this new function?  I don't see how its related to this
CL.

+#define DECLARE_OPCODE(type) \
+  case Opcode::k##type:      \
+    return #type;
+    LITHIUM_CONCRETE_INSTRUCTION_LIST(DECLARE_OPCODE)
+#undef DECLARE_OPCODE
+    default:
+      return NULL;
+  }
+}
+
 #ifdef DEBUG
 void LInstruction::VerifyCall() {
   // Call instructions can use only fixed registers as temporaries and
@@ -1353,12 +1365,6 @@ LInstruction* LChunkBuilder::DoSub(HSub* instr) {
     DCHECK(instr->left()->representation().Equals(instr->representation()));
     DCHECK(instr->right()->representation().Equals(instr->representation()));
 
-    if (instr->left()->IsConstant() &&
-        !instr->CheckFlag(HValue::kCanOverflow)) {
-      // If lhs is constant, do reverse subtraction instead.
-      return DoRSub(instr);
-    }
-
     LOperand* left = UseRegisterAtStart(instr->left());
     LOperand* right = UseOrConstantAtStart(instr->right());
     LSubI* sub = new (zone()) LSubI(left, right);
@@ -1374,21 +1380,6 @@ LInstruction* LChunkBuilder::DoSub(HSub* instr) {
   }
 }
 
-LInstruction* LChunkBuilder::DoRSub(HSub* instr) {
-  DCHECK(instr->representation().IsSmiOrInteger32());
-  DCHECK(instr->left()->representation().Equals(instr->representation()));
-  DCHECK(instr->right()->representation().Equals(instr->representation()));
-  DCHECK(!instr->CheckFlag(HValue::kCanOverflow));
-
-  // Note: The lhs of the subtraction becomes the rhs of the
-  // reverse-subtraction.
-  LOperand* left = UseRegisterAtStart(instr->right());
-  LOperand* right = UseOrConstantAtStart(instr->left());
-  LRSubI* rsb = new (zone()) LRSubI(left, right);
-  LInstruction* result = DefineAsRegister(rsb);
-  return result;
-}
-
 LInstruction* LChunkBuilder::DoMultiplyAdd(HMul* mul, HValue* addend) {
   LOperand* multiplier_op = UseRegister(mul->left());
   LOperand* multiplicand_op = UseRegister(mul->right());