Update default mcpu values to not use SSSE3 and tune for pre-sandybridge CPUs

pnacl/driver/pnacl-translate.py

 #!/usr/bin/python
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # IMPORTANT NOTE: If you make local mods to this file, you must run:
 #   %  pnacl/build.sh driver
 # in order for them to take effect in the scons build.  This command
 # updates the copy in the toolchain/ tree.
 #
@@ skipping 221 matching lines @@
         'mac': {'X8632': 'i686-apple-darwin'}}
   env.set('TRIPLE', triple_map[env.getone('TARGET_OS')][base_arch])
 
   # CPU that is representative of baseline feature requirements for NaCl
   # and/or chrome.  We may want to make this more like "-mtune"
   # by specifying both "-mcpu=X" and "-mattr=+feat1,-feat2,...".
   # Note: this may be different from the in-browser translator, which may
   # do auto feature detection based on CPUID, but constrained by what is
   # accepted by NaCl validators.
   cpu_map = {
-      'X8632': 'pentium4',
-      'X8664': 'core2',
+      'X8632': 'pentium4m',
+      'X8664': 'x86-64',
       'ARM': 'cortex-a9',
       'MIPS32': 'mips32r2'}
   env.set('LLC_MCPU', '-mcpu=%s' % cpu_map[base_arch])
 
   llc_flags_map = {
       'ARM': ['-float-abi=hard', '-mattr=+neon'],
       # Once PNaCl's build of compiler-rt (libgcc.a) defines __aeabi_*
       # functions, we can drop the following ad-hoc option.
       'ARM_NONSFI': ['-arm-enable-aeabi-functions=0'],
       }
@@ skipping 241 matching lines @@
 
 ADVANCED OPTIONS:
   -mattr=<+feat1,-feat2>  Toggle specific cpu features on and off.
   -mcpu=<cpu-name>        Target a specific cpu type.  Tunes code as well as
                           turns cpu features on and off.
   -S                      Generate native assembly only.
   -c                      Generate native object file only.
   --pnacl-sb              Use the translator which runs inside the NaCl sandbox.
   -O[0-3]                 Change translation-time optimization level.
 """