Add support for `-DNO_ASM`

[mirabilos]

Ideally, #if defined(NO_ASM), disable all attempts to use assembly code. No x86 specials, no ARM specials, etc.

The wild growth of things to define to make a portable build is suboptimal.

[mirabilos]

Incidentally, this will also be needed to prevent build failures such as:

mkdep -a -DBLAKE3_NO_SSE2 -DBLAKE3_NO_SSE41 -DBLAKE3_NO_AVX2 -DBLAKE3_NO_AVX512 -idirafter /tmp/b/s /tmp/b/s/blake3.c /tmp/b/s/blake3_dispatch.c /tmp/b/s/blake3_portable.c
/tmp/b/s/blake3_dispatch.c:15:23: immintrin.h: No such file or directory

(This is an older GCC on i386 with an 80486DX baseline.)

[mirabilos]

This could look like this:

--- /tmp/b/BLAKE3-1.8.2/c/blake3_impl.h	Sun Apr 20 23:42:05 2025
+++ blake3_impl.h	Thu Jan  1 18:26:52 2026
@@ -38,6 +38,7 @@
 #define NOEXCEPT
 #endif
 
+#ifndef NO_ASM
 #if (defined(__x86_64__) || defined(_M_X64)) && !defined(_M_ARM64EC)
 #define IS_X86
 #define IS_X86_64
@@ -57,10 +58,11 @@
 #include <intrin.h>
 #endif
 #endif
+#endif
 
 #if !defined(BLAKE3_USE_NEON) 
   // If BLAKE3_USE_NEON not manually set, autodetect based on AArch64ness
-  #if defined(IS_AARCH64)
+  #if defined(IS_AARCH64) && !defined(NO_ASM)
     #if defined(__ARM_BIG_ENDIAN)
       #define BLAKE3_USE_NEON 0
     #else

With this, I can at least build it (now, to figure out where you hid the .so.MAJOR.MINOR version…)

[BurningEnlightenment]

I'm not entirely sure whether I understand the use case. Why wouldn't you want to build with runtime dispatching for x86? (Btw. the CMake buildsystem already has -DBLAKE3_SIMD_TYPE=none which stamps out everything but the generic implemetation #510)

(This is an older GCC on i386 with an 80486DX baseline.)

Which version exactly? And why can't you use a modern one?

[mirabilos]

Henrik Gaßmann dixit:

BurningEnlightenment left a comment (BLAKE3-team/BLAKE3#537) I'm not entirely sure whether I understand the use case. Why wouldn't you want to build with runtime dispatching for x86?

Because the system does not support SSE2 and the likes?

(Btw. the CMake buildsystem already has `-DBLAKE3_SIMD_TYPE=none` which stamps out everything but the generic implemetation #510)

Perhaps, but, ugh cmake.

> (This is an older GCC on i386 with an 80486DX baseline.) Which version exactly? And why can't you use a modern one?

3.4.6, which is the system compiler on this BSD. The idea was to add the hash to the base system. Newer ones produce larger code (even with -Os) so the boot floppy doesn’t fit any more, have reduced support for sparc (v7/v8, not v8+/v9), have a more restrictive licence and lack GPC support. bye, //mirabilos -- „Cool, /usr/share/doc/mksh/examples/uhr.gz ist ja ein Grund, mksh auf jedem System zu installieren.“ -- XTaran auf der OpenRheinRuhr, ganz begeistert (EN: “[…]uhr.gz is a reason to install mksh on every system.”)

[BurningEnlightenment]

Ah, I see. I've considered refactoring the dispatch logic in a way which allows for simply exposing the implementation if the library is compiled with a single implementation. This could also benefit the Gentoo port as people usually compile for their native feature set. I've in fact implemented this for my libb2 fork here: deeplex/libb2-reforged@a71a96e

@oconnor663 would you be open to accept a refactoring of the dispatch logic?