ARM: Emit RSB (reverse-subtract) for subtraction with constant lhs

src/arm/lithium-codegen-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1601 matching lines @@
     ASSERT(right->IsRegister() || right->IsConstantOperand());
     __ sub(ToRegister(result), ToRegister(left), ToOperand(right), set_cond);
   }
 
   if (can_overflow) {
     DeoptimizeIf(vs, instr->environment());
   }
 }
 
 
+void LCodeGen::DoRSubI(LRSubI* instr) {
+  LOperand* left = instr->left();
+  LOperand* right = instr->right();
+  LOperand* result = instr->result();
+  bool can_overflow = instr->hydrogen()->CheckFlag(HValue::kCanOverflow);
+  SBit set_cond = can_overflow ? SetCC : LeaveCC;
+
+  if (right->IsStackSlot() || right->IsArgument()) {
+    Register right_reg = EmitLoadRegister(right, ip);
+    __ rsb(ToRegister(result), ToRegister(left), Operand(right_reg), set_cond);
+  } else {
+    ASSERT(right->IsRegister() || right->IsConstantOperand());
+    __ rsb(ToRegister(result), ToRegister(left), ToOperand(right), set_cond);
+  }
+
+  if (can_overflow) {
+    DeoptimizeIf(vs, instr->environment());
+  }
+}
+
+
 void LCodeGen::DoConstantI(LConstantI* instr) {
   ASSERT(instr->result()->IsRegister());
   __ mov(ToRegister(instr->result()), Operand(instr->value()));
 }
 
 
 void LCodeGen::DoConstantD(LConstantD* instr) {
   ASSERT(instr->result()->IsDoubleRegister());
   DwVfpRegister result = ToDoubleRegister(instr->result());
   double v = instr->value();
@@ skipping 4118 matching lines @@
   __ sub(scratch, result, Operand(index, LSL, kPointerSizeLog2 - kSmiTagSize));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal