From 0fb613f88e44dc877a1b99cf324af6809a8391fd Mon Sep 17 00:00:00 2001
From: Jim Stichnoth <stichnot@chromium.org>
Date: Tue, 16 Sep 2014 10:19:03 -0700
Subject: [PATCH] Subzero: Make the szbuild.py script more automatic.

One wants to omit the --init option to make things go faster, but then there's the risk that the pexe or llvm2ice or llc has changed and --init is actually necessary.

This change automatically compares the modification timestamps of the pexe and the llvm2ice and llc binaries against the modification timestamps of the object files to determine whether re-translation is needed.

The --init option forces re-translation regardless of timestamps.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/551373008
---
 pydir/szbuild.py | 51 ++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 17 deletions(-)

diff --git a/pydir/szbuild.py b/pydir/szbuild.py
index dd94bda7d..e922190b9 100755
--- a/pydir/szbuild.py
+++ b/pydir/szbuild.py
@@ -9,6 +9,15 @@ import sys
 from utils import shellcmd
 from utils import FindBaseNaCl
 
+def NewerThanOrNotThere(old_path, new_path):
+    """Returns whether old_path is newer than new_path.
+
+    Also returns true if either path doesn't exist.
+    """
+    if not (os.path.exists(old_path) and os.path.exists(new_path)):
+        return True
+    return os.path.getmtime(old_path) > os.path.getmtime(new_path)
+
 def BuildRegex(patterns, syms):
     """Build a regular expression string for inclusion or exclusion.
 
@@ -79,14 +88,14 @@ def main():
     notation, so e.g. use '0:10' or ':10' for the first 10 lines of
     the file, or '1' for the second line of the file.
 
-    The --init argument does first-time initialization for the pexe,
-    including creation of the Subzero symbol file that is implicitly
-    used in the --include and --exclude arguments.  It can be removed
-    from the command line for subsequent executions if the pexe
-    doesn't change.
+    This script uses file modification timestamps to determine whether
+    llc and Subzero re-translation are needed.  It checks timestamps
+    of llc, llvm2ice, and the pexe against the translated object files
+    to determine the minimal work necessary.  The --force option
+    suppresses those checks and re-translates everything.
 
-    This scripts augments PATH so that various PNaCl and LLVM tools
-    can be run.  These extra paths are within the native_client tree.
+    This script augments PATH so that various PNaCl and LLVM tools can
+    be run.  These extra paths are within the native_client tree.
     When changes are made to these tools, copy them this way:
       cd native_client
       toolchain_build/toolchain_build_pnacl.py llvm_i686_linux \\
@@ -96,8 +105,8 @@ def main():
         description='    ' + main.__doc__,
         formatter_class=argparse.RawTextHelpFormatter)
     argparser.add_argument('pexe', help='Finalized pexe to translate')
-    argparser.add_argument('--init', dest='init', action='store_true',
-                           help='Perform first-time setup for the pexe')
+    argparser.add_argument('--force', dest='force', action='store_true',
+                           help='Force all re-translations of the pexe')
     argparser.add_argument('--include', '-i', default=[], dest='include',
                            action='append',
                            help='Subzero symbols to include ' +
@@ -145,9 +154,16 @@ def main():
     sym_sz_unescaped = pexe_base_unescaped + '.sym.sz.txt'
     whitelist_sz = pexe_base + '.wl.sz.txt'
     whitelist_sz_unescaped = pexe_base_unescaped + '.wl.sz.txt'
+    llvm2ice = (
+        '{root}/toolchain_build/src/subzero/llvm2ice'
+        ).format(root=nacl_root)
+    llcbin = (
+        '{root}/toolchain/linux_x86/pnacl_newlib/host_x86_32/bin/llc'
+        ).format(root=nacl_root)
+    opt_level = args.optlevel
 
-    if args.init:
-        opt_level = args.optlevel
+    if args.force or NewerThanOrNotThere(pexe, obj_llc) or \
+            NewerThanOrNotThere(llcbin, obj_llc):
         opt_level_map = { 'm1':'0', '-1':'0', '0':'0', '1':'1', '2':'2' }
         shellcmd((
             'pnacl-translate -ffunction-sections -c -arch x86-32-linux ' +
@@ -159,10 +175,14 @@ def main():
             'objcopy --redefine-sym _start=_user_start {obj}'
             ).format(obj=obj_llc), echo=args.verbose)
         shellcmd((
-            '{root}/toolchain_build/src/subzero/llvm2ice ' +
-            '-O{level} -bitcode-format=pnacl -disable-globals ' +
+            'nm {obj} | sed -n "s/.* [a-zA-Z] //p" > {sym}'
+            ).format(obj=obj_llc, sym=sym_llc), echo=args.verbose)
+    if args.force or NewerThanOrNotThere(pexe, obj_sz) or \
+            NewerThanOrNotThere(llvm2ice, obj_sz):
+        shellcmd((
+            '{l2i} -O{level} -bitcode-format=pnacl -disable-globals ' +
             '-externalize -ffunction-sections {pexe} -o {asm}'
-            ).format(root=nacl_root,level=opt_level, pexe=pexe, asm=asm_sz),
+            ).format(l2i=llvm2ice, level=opt_level, pexe=pexe, asm=asm_sz),
                  echo=args.verbose)
         shellcmd((
             'llvm-mc -arch=x86 -x86-asm-syntax=intel -filetype=obj -o {obj} ' +
@@ -174,9 +194,6 @@ def main():
         shellcmd((
             'nm {obj} | sed -n "s/.* [a-zA-Z] //p" > {sym}'
             ).format(obj=obj_sz, sym=sym_sz), echo=args.verbose)
-        shellcmd((
-            'nm {obj} | sed -n "s/.* [a-zA-Z] //p" > {sym}'
-            ).format(obj=obj_llc, sym=sym_llc), echo=args.verbose)
 
     with open(sym_sz_unescaped) as f:
         sz_syms = f.read().splitlines()
-- 
2.11.0