X64: Change testl to testb if mask fits in 1 byte. Shortens smi test.

src/x64/assembler-x64.cc

 // Copyright 2009 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 1590 matching lines @@
 void Assembler::testl(Register dst, Register src) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   emit_optional_rex_32(dst, src);
   emit(0x85);
   emit_modrm(dst, src);
 }
 
 
 void Assembler::testl(Register reg, Immediate mask) {
+  // testl with a mask that fits in the low byte is exactly testb.
+  if (is_uint8(mask.value_) {
+    testb(reg, mask);
+    return;
+  }
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   if (reg.is(rax)) {
     emit(0xA9);
     emit(mask);
   } else {
     emit_optional_rex_32(rax, reg);
     emit(0xF7);
     emit_modrm(0x0, reg);
     emit(mask);
   }
 }
 
 
 void Assembler::testl(const Operand& op, Immediate mask) {
+  // testl with a mask that fits in the low byte is exactly testb.
+  if (is_uint8(mask.value_)) {
+    testb(op, mask);
+    return;
+  }
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
   emit_optional_rex_32(rax, op);
   emit(0xF7);
   emit_operand(rax, op);  // Operation code 0
   emit(mask);
 }
 
 
 void Assembler::testq(const Operand& op, Register reg) {
@@ skipping 588 matching lines @@
     RecordRelocInfo(RelocInfo::POSITION, current_position_);
     written_position_ = current_position_;
   }
 }
 
 
 const int RelocInfo::kApplyMask = 1 << RelocInfo::INTERNAL_REFERENCE;
 
 
 } }  // namespace v8::internal