vpx/build/make/ads2armasm_ms.pl
Martin Storsjo 5182befa49 ads2armasm_ms: Add an ALIGN 4 after ENDP
This makes sure that labels for data symbols directly after
functions get properly 4-byte-aligned (when the source is assembled
in thumb mode).

Previously, if declaring a data symbol directly after a function, the
symbol could end up pointing to the unaligned address (if the total
size of the thumb function didn't end up being a multiple of 4). The
data in the symbol itself ended up aligned, but the symbol pointed to
the preceding unaligned position.

That is, a source file looking like this:
---
   ...
   ENDP

symbol
   DCD 0x12345678
---

could end up being assembled into
symbol:
  xxxxx2: 0000
  xxxxx4: 5678
  xxxxx6: 1234

(This doesn't happen if the symbol label is on the same line as the
DCD directive.)

By adding an ALIGN 4 directly after the ENDP we make sure the symbol
itself gets aligned properly.

This isn't an issue with the original, untranslated arm source,
since it only is built in arm mode where all instructions are 4 byte,
and since the gnu assembler automatically adds the padding before the
symbol even in thumb mode.

Change-Id: Iadbeebd656b0197e423e79a12a7d3ef8859cf445
2014-03-19 21:53:44 +02:00

40 lines
915 B
Perl
Executable File

#!/usr/bin/env perl
##
## Copyright (c) 2013 The WebM 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 in the root of the source
## tree. An additional intellectual property rights grant can be found
## in the file PATENTS. All contributing project authors may
## be found in the AUTHORS file in the root of the source tree.
##
use FindBin;
use lib $FindBin::Bin;
use thumb;
print "; This file was created from a .asm file\n";
print "; using the ads2armasm_ms.pl script.\n";
while (<STDIN>)
{
undef $comment;
undef $line;
s/REQUIRE8//;
s/PRESERVE8//;
s/^\s*ARM\s*$//;
s/AREA\s+\|\|(.*)\|\|/AREA |$1|/;
s/qsubaddx/qsax/i;
s/qaddsubx/qasx/i;
thumb::FixThumbInstructions($_, 1);
s/ldrneb/ldrbne/i;
s/ldrneh/ldrhne/i;
s/(ENDP.*)/$&\n ALIGN 4/;
print;
}