[turbofan]: More optimizations to add and subtract operations on x64

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index e1eb92f12bb09436d57d519a771e40ffabacad46..051ff9f5f42c61a1cdf3723f3bfd8e2746d8d96b 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -597,6 +597,12 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kX64Lea:
       __ leaq(i.OutputRegister(), i.MemoryOperand());
       break;
+    case kX64Dec32:
+      __ decl(i.OutputRegister());
+      break;
+    case kX64Inc32:
+      __ incl(i.OutputRegister());
+      break;
     case kX64Push:
       if (HasImmediateInput(instr, 0)) {
         __ pushq(i.InputImmediate(0));