[turbofan] Recognize sign extension of 8-bit and 16-bit values on arm64.

src/compiler/arm64/code-generator-arm64.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/code-generator.h"
 
 #include "src/arm64/macro-assembler-arm64.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 398 matching lines @@
       break;
     case kArm64Ror:
       ASSEMBLE_SHIFT(Ror, 64);
       break;
     case kArm64Ror32:
       ASSEMBLE_SHIFT(Ror, 32);
       break;
     case kArm64Mov32:
       __ Mov(i.OutputRegister32(), i.InputRegister32(0));
       break;
+    case kArm64Sxtb32:
+      __ Sxtb(i.OutputRegister32(), i.InputRegister32(0));
+      break;
+    case kArm64Sxth32:
+      __ Sxth(i.OutputRegister32(), i.InputRegister32(0));
+      break;
     case kArm64Sxtw:
       __ Sxtw(i.OutputRegister(), i.InputRegister32(0));
       break;
     case kArm64Ubfx:
       __ Ubfx(i.OutputRegister(), i.InputRegister(0), i.InputInt8(1),
               i.InputInt8(2));
       break;
     case kArm64Ubfx32:
       __ Ubfx(i.OutputRegister32(), i.InputRegister32(0), i.InputInt8(1),
               i.InputInt8(2));
@@ skipping 578 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8