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arm: Add a placeholder file in lieu of the former filter_neon.S

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In the previous commit 9e538750d99c8f1accf7e93878e4fde47c069908
we removed the obsolete assembler implementation `filter_neon.S`.

In this commit we add a stand-in for the original file, restoring
the original source tree structure, for the benefit of continuing
hassle-free libpng source upgrades in the 1.6.x line.
This commit is contained in:
Cosmin Truta 2024-06-17 15:28:38 +03:00
parent 9e538750d9
commit e4a31f024b
1 changed files with 61 additions and 0 deletions
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arm/filter_neon.S Normal file
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/* filter_neon.S - placeholder file
*
* Copyright (c) 2024 Cosmin Truta
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*/
/* IMPORTANT NOTE:
*
* Historically, the hand-coded assembler implementation of Neon optimizations
* in this module had not been in sync with the intrinsics-based implementation
* in filter_neon_intrinsics.c and palette_neon_intrinsics.c, at least since
* the introduction of riffled palette optimizations. Moreover, the assembler
* code used to work on 32-bit ARM only, and it caused problems, even if empty,
* on 64-bit ARM.
*
* All references to this module from our internal build scripts and projects
* have been removed.
*
* For the external projects that might still expect this module to be present,
* we leave this stub in place, for the remaining lifetime of libpng-1.6.x.
* Everything should continue to function normally, as long as there are no
* deliberate attempts to use the old hand-made assembler code. A build error
* will be raised otherwise.
*/
/* This is required to get the symbol renames, which are #defines, and the
* definitions (or not) of PNG_ARM_NEON_OPT and PNG_ARM_NEON_IMPLEMENTATION.
*/
#define PNG_VERSION_INFO_ONLY
#include "../pngpriv.h"
#ifdef PNG_READ_SUPPORTED
#if PNG_ARM_NEON_IMPLEMENTATION == 2 /* hand-coded assembler */
#if PNG_ARM_NEON_OPT > 0
#if defined(__clang__)
#define GNUC_VERSION 0 /* not gcc, although it might pretend to be */
#elif defined(__GNUC__)
#define GNUC_MAJOR (__GNUC__ + 0)
#define GNUC_MINOR (__GNUC_MINOR__ + 0)
#define GNUC_PATCHLEVEL (__GNUC_PATCHLEVEL__ + 0)
#define GNUC_VERSION (GNUC_MAJOR * 10000 + GNUC_MINOR * 100 + GNUC_PATCHLEVEL)
#else
#define GNUC_VERSION 0 /* not gcc */
#endif
#if (GNUC_VERSION > 0) && (GNUC_VERSION < 40300)
#error "PNG_ARM_NEON is not supported with gcc versions earlier than 4.3.0"
#elif GNUC_VERSION == 40504
#error "PNG_ARM_NEON is not supported with gcc version 4.5.4"
#else
#error "Please use 'arm/*_neon_intrinsics.c' for PNG_ARM_NEON support"
#endif
#endif /* PNG_ARM_NEON_OPT > 0 */
#endif /* PNG_ARM_NEON_IMPLEMENTATION == 2 */
#endif /* READ */