Subzero: Add a --elf arg to szbuild.py and crosstest.py.

pydir/crosstest.py

 #!/usr/bin/env python2
 
 import argparse
 import os
 import re
 import subprocess
 import sys
 import tempfile
 
 from utils import shellcmd
@@ skipping 47 matching lines @@
     argparser.add_argument('--dir', required=False, default='.',
                            metavar='OUTPUT_DIR',
                            help='Output directory for all files.' +
                                 ' Default "%(default)s".')
     argparser.add_argument('--crosstest-bitcode', required=False,
                            default=1, type=int,
                            help='Compile non-subzero crosstest object file ' +
                            'from the same bitcode as the subzero object. ' +
                            'If 0, then compile it straight from source.' +
                            ' Default %(default)d.')
+    argparser.add_argument('--elf', dest='elf',
+                           action='store_true',
+                           help='Directly generate ELF output')
     args = argparser.parse_args()
 
     nacl_root = FindBaseNaCl()
     # Prepend PNaCl bin to $PATH.
     os.environ['PATH'] = nacl_root + \
         '/toolchain/linux_x86/pnacl_newlib/bin' + \
         os.pathsep + os.environ['PATH']
 
     objs = []
     remove_internal = re.compile('^define internal ')
@@ skipping 20 matching lines @@
         base_sz = '%s.O%s.%s.%s' % (base, args.optlevel, args.attr, args.target)
         asm_sz = os.path.join(args.dir, base_sz + '.sz.s')
         obj_sz = os.path.join(args.dir, base_sz + '.sz.o')
         obj_llc = os.path.join(args.dir, base + '.llc.o')
         shellcmd(['../llvm2ice',
                   '-O' + args.optlevel,
                   '-mattr=' + args.attr,
                   '--target=' + args.target,
                   '--prefix=' + args.prefix,
                   '-allow-uninitialized-globals',
-                  '-o=' + asm_sz,
-                  bitcode])
-        shellcmd(['llvm-mc',
-                  '-arch=' + arch_map[args.target],
-                  '-filetype=obj',
-                  '-o=' + obj_sz,
-                  asm_sz])
+                  '-o=' + (obj_sz if args.elf else asm_sz),
+                  bitcode] +
+                 (['-elf-writer'] if args.elf else []))
+        if not args.elf:
+            shellcmd(['llvm-mc',
+                      '-arch=' + arch_map[args.target],
+                      '-filetype=obj',
+                      '-o=' + obj_sz,
+                      asm_sz])
         objs.append(obj_sz)
         # Each original bitcode file needs to be translated by the
         # LLVM toolchain and have its object file linked in.  There
         # are two ways to do this: explicitly use llc, or include the
         # .ll file in the link command.  It turns out that these two
         # approaches can produce different semantics on some undefined
         # bitcode behavior.  Specifically, LLVM produces different
         # results for overflowing fptoui instructions for i32 and i64
         # on x86-32.  As it turns out, Subzero lowering was based on
         # inspecting the object code produced by the direct llc
@@ skipping 18 matching lines @@
     objs.append((
             '{root}/toolchain_build/src/subzero/runtime/szrt.{ext}'
             ).format(root=nacl_root, ext='c' if pure_c else 'cpp'))
     objs.append((
             '{root}/toolchain_build/src/subzero/runtime/szrt_i686.ll'
             ).format(root=nacl_root))
     linker = 'clang' if pure_c else 'clang++'
     shellcmd([linker, '-g', '-m32', args.driver] +
              objs +
              ['-lm', '-lpthread', '-o', os.path.join(args.dir, args.output)])