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configure: add --enable-aligned

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forces aligned memory reads (via memcpy) in the VP8 bit reader, useful
for platforms that don't support unaligned loads.

Change-Id: Ifa44a9a1677fbdc6a929520f9340b7e3fcbd6692
This commit is contained in:
James Zern 2014-07-03 23:06:06 -07:00
parent 380cca4f2c
commit dc0f479d6a
2 changed files with 25 additions and 1 deletions
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13
configure.ac
View File

@ -410,6 +410,19 @@ if test "$target_os" = "mingw32" -a "$enable_wic" = "yes"; then
fi
fi
dnl === If --enable-aligned is defined, define WEBP_FORCE_ALIGNED
AC_MSG_CHECKING(if --enable-aligned option is specified)
AC_ARG_ENABLE([aligned],
AS_HELP_STRING([--enable-aligned],
[Force aligned memory operations in non-dsp code
(may be slower)]))
if test "$enable_aligned" = "yes"; then
AC_DEFINE(WEBP_FORCE_ALIGNED, [1],
[Define to 1 to force aligned memory operations])
fi
AC_MSG_RESULT(${enable_aligned-no})
dnl === If --enable-swap-16bit-csp is defined, add -DWEBP_SWAP_16BIT_CSP
USE_SWAP_16BIT_CSP=""

13
src/utils/bit_reader_inl.h
View File

@ -16,6 +16,14 @@
#ifndef WEBP_UTILS_BIT_READER_INL_H_
#define WEBP_UTILS_BIT_READER_INL_H_
#ifdef HAVE_CONFIG_H
#include "../webp/config.h"
#endif
#ifdef WEBP_FORCE_ALIGNED
#include <string.h> // memcpy
#endif
#include "./bit_reader.h"
#include "./endian_inl.h"
@ -52,7 +60,10 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
if (br->buf_ + sizeof(lbit_t) <= br->buf_end_) {
// convert memory type to register type (with some zero'ing!)
bit_t bits;
#if defined(__mips__) // MIPS
#if defined(WEBP_FORCE_ALIGNED)
lbit_t in_bits;
memcpy(&in_bits, br->buf_, sizeof(in_bits));
#elif defined(__mips__) // MIPS
// This is needed because of un-aligned read.
lbit_t in_bits;
lbit_t* p_buf_ = (lbit_t*)br->buf_;