1 OPERATING SYSTEM SPECIFIC ARM NEON DETECTION 2 -------------------------------------------- 3 4 Detection of the ability to exexcute ARM NEON on an ARM processor requires 5 operating system support. (The information is not available in user mode.) 6 7 HOW TO USE THIS 8 --------------- 9 10 This directory contains C code fragments that can be included in arm/arm_init.c 11 by setting the macro PNG_ARM_NEON_FILE to the file name in "" or <> at build 12 time. This setting is not recorded in pnglibconf.h and can be changed simply by 13 rebuilding arm/arm_init.o with the required macro definition. 14 15 For any of this code to be used the ARM NEON code must be enabled and run time 16 checks must be supported. I.e.: 17 18 #if PNG_ARM_NEON_OPT > 0 19 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED 20 21 This is done in a 'configure' build by passing configure the argument: 22 23 --enable-arm-neon=check 24 25 Apart from the basic Linux implementation in contrib/arm-neon/linux.c this code 26 is unsupported. That means that it is not even compiled on a regular basis and 27 may be broken in any given minor release. 28 29 FILE FORMAT 30 ----------- 31 32 Each file documents its testing status as of the last time it was tested (which 33 may have been a long time ago): 34 35 STATUS: one of: 36 SUPPORTED: This indicates that the file is included in the regularly 37 performed test builds and bugs are fixed when discovered. 38 COMPILED: This indicates that the code did compile at least once. See the 39 more detailed description for the extent to which the result was 40 successful. 41 TESTED: This means the code was fully compiled into the libpng test programs 42 and these were run at least once. 43 44 BUG REPORTS: an email address to which to send reports of problems 45 46 The file is a fragment of C code. It should not define any 'extern' symbols; 47 everything should be static. It must define the function: 48 49 static int png_have_neon(png_structp png_ptr); 50 51 That function must return 1 if ARM NEON instructions are supported, 0 if not. 52 It must not execute png_error unless it detects a bug. A png_error will prevent 53 the reading of the PNG and in the future, writing too. 54 55 BUG REPORTS 56 ----------- 57 58 If you mail a bug report for any file that is not SUPPORTED there may only be 59 limited response. Consider fixing it and sending a patch to fix the problem - 60 this is more likely to result in action. 61 62 CONTRIBUTIONS 63 ------------- 64 65 You may send contributions of new implementations to 66 png-mng-implement (a] sourceforge.net. Please write code in strict C90 C where 67 possible. Obviously OS dependencies are to be expected. If you submit code you 68 must have the authors permission and it must have a license that is acceptable 69 to the current maintainer; in particular that license must permit modification 70 and redistribution. 71 72 Please try to make the contribution a single file and give the file a clear and 73 unambiguous name that identifies the target OS. If multiple files really are 74 required put them all in a sub-directory. 75 76 You must also be prepared to handle bug reports from users of the code, either 77 by joining the png-mng-implement mailing list or by providing an email for the 78 "BUG REPORTS" entry or both. Please make sure that the header of the file 79 contains the STATUS and BUG REPORTS fields as above. 80 81 Please list the OS requirements as precisely as possible. Ideally you should 82 also list the environment in which the code has been tested and certainly list 83 any environments where you suspect it might not work. 84
