build: Prefer NASM assembler over YASM

NASM is more actively maintained and permits generating dependency information
as a sideeffect of assembling, thus cutting build times in half.

.travis.yml

@@ -6,7 +6,7 @@ os:
 addons:
   apt:
     packages:
-      - yasm
+      - nasm
       - diffutils
 compiler:
   - clang
@@ -17,7 +17,7 @@ cache:
 before_install:
   - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew update --all; fi
 install:
-  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew install yasm; fi
+  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew install nasm; fi
 script:
   - mkdir -p libav-samples
   - ./configure --samples=libav-samples --cc=$CC

Changelog

@@ -9,6 +9,8 @@ version <next>:
 - config.log and other configuration files moved into avbuild/ directory
 - VAAPI-accelerated MPEG-2 and VP8 encoding
 - Apple Pixlet decoder
+- The x86 assembler default switched from yasm to nasm, pass
+  --x86asmexe=yasm to configure to restore the old behavior.
 
 
 version 12:

configure

@@ -2563,7 +2563,7 @@ shlibdir_default="$libdir_default"
 ar_default="ar"
 cc_default="gcc"
 host_cc_default="gcc"
-x86asmexe_default="yasm"
+x86asmexe_default="nasm"
 ln_s="ln -s -f"
 nm_default="nm -g"
 pkg_config_default=pkg-config
@@ -4493,7 +4493,7 @@ EOF
     }
 
     if ! disabled_any asm mmx x86asm; then
-        for program in $x86asmexe yasm nasm; do
+        for program in $x86asmexe nasm yasm; do
             probe_x86asm $program
             test -n "$x86asm_type" && break
         done
@@ -4505,7 +4505,7 @@ EOF
         esac
 
         check_x86asm "movbe ecx, [5]" && enable x86asm ||
-            die "yasm/nasm not found or too old. Use --disable-x86asm for a crippled build."
+            die "nasm/yasm not found or too old. Use --disable-x86asm for a crippled build."
         check_x86asm "vextracti128 xmm0, ymm0, 0"      || disable avx2_external
         check_x86asm "vpmacsdd xmm0, xmm1, xmm2, xmm3" || disable xop_external
         check_x86asm "vfmadd132ps ymm0, ymm1, ymm2"    || disable fma3_external

doc/optimization.txt

@@ -161,8 +161,8 @@ do{
 For x86, mark registers that are clobbered in your asm. This means both
 general x86 registers (e.g. eax) as well as XMM registers. This last one is
 particularly important on Win64, where xmm6-15 are callee-save, and not
-restoring their contents leads to undefined results. In external asm (e.g.
+restoring their contents leads to undefined results. In external asm,
-yasm), you do this by using:
+you do this by using:
 cglobal function_name, num_args, num_regs, num_xmm_regs
 In inline asm, you specify clobbered registers at the end of your asm:
 __asm__(".." ::: "%eax").
@@ -194,12 +194,12 @@ The latter requires a good optimizing compiler which gcc is not.
 Inline asm vs. external asm
 ---------------------------
 Both inline asm (__asm__("..") in a .c file, handled by a compiler such as gcc)
-and external asm (.s or .asm files, handled by an assembler such as yasm/nasm)
+and external asm (.s or .asm files, handled by an assembler such as nasm/yasm)
 are accepted in Libav. Which one to use differs per specific case.
 
 - if your code is intended to be inlined in a C function, inline asm is always
    better, because external asm cannot be inlined
-- if your code calls external functions, yasm is always better
+- if your code calls external functions, external asm is always better
 - if your code takes huge and complex structs as function arguments (e.g.
    MpegEncContext; note that this is not ideal and is discouraged if there
    are alternatives), then inline asm is always better, because predicting

doc/platform.texi

@@ -69,9 +69,9 @@ OS X on PowerPC or ARM (iPhone) requires a preprocessor from
 assembly functions. Put the Perl script somewhere
 in your PATH, Libav's configure will pick it up automatically.
 
-OS X on AMD64 and x86 requires @command{yasm} to build most of the
+OS X on AMD64 and x86 requires @command{nasm} to build most of the
 optimized assembly functions @url{http://mxcl.github.com/homebrew/, Homebrew},
-@url{http://www.gentoo.org/proj/en/gentoo-alt/prefix/bootstrap-macos.xml, Gentoo Prefix}
+@url{https://wiki.gentoo.org/wiki/Project:Prefix, Gentoo Prefix}
 or @url{http://www.macports.org, MacPorts} can easily provide it.
 
 
@@ -134,7 +134,7 @@ them under @command{MinGW-w64 Win64 Shell} and @command{MinGW-w64 Win32 Shell}.
 pacman -S make pkgconf diffutils
 
 # mingw-w64 packages and toolchains
-pacman -S mingw-w64-x86_64-yasm mingw-w64-x86_64-gcc mingw-w64-x86_64-SDL
+pacman -S mingw-w64-x86_64-nasm mingw-w64-x86_64-gcc mingw-w64-x86_64-SDL
 @end example
 
 To target 32 bits replace @code{x86_64} with @code{i686} in the command above.
@@ -152,14 +152,14 @@ You will need the following prerequisites:
 @item @uref{http://code.google.com/p/msinttypes/, msinttypes}
 (if using MSVC 2012 or earlier)
 @item @uref{http://msys2.github.io/, MSYS2}
-@item @uref{http://yasm.tortall.net/, YASM}
+@item @uref{http://www.nasm.us/, NASM}
 (Also available via MSYS2's package manager.)
 @end itemize
 
 To set up a proper environment in MSYS2, you need to run @code{msys_shell.bat} from
 the Visual Studio or Intel Compiler command prompt.
 
-Place @code{yasm.exe} somewhere in your @code{PATH}. If using MSVC 2012 or
+Place @code{nasm.exe} somewhere in your @code{PATH}. If using MSVC 2012 or
 earlier, place @code{c99wrap.exe} and @code{c99conv.exe} somewhere in your
 @code{PATH} as well.
 
@@ -307,7 +307,7 @@ These library packages are only available from
 @uref{http://sourceware.org/cygwinports/, Cygwin Ports}:
 
 @example
-yasm, libSDL-devel, libfaac-devel, libgsm-devel, libmp3lame-devel,
+nasm, libSDL-devel, libfaac-devel, libgsm-devel, libmp3lame-devel,
 libschroedinger1.0-devel, speex-devel, libtheora-devel, libxvidcore-devel
 @end example