tree dc4b94cce8dcfbd4a233b5367a5558b428a5ea48
parent 5e0b2ae0d5090aa89a321af03875000a8cfd58fb
author Nigel Tao <nigeltao@golang.org> 1722409975 +1000
committer Nigel Tao <nigeltao@golang.org> 1722409975 +1000

base: disable SIMD on MSVC x86_64 by default

This recreates the case as of commit f1698226 (tag v0.4.0-alpha.4), in
that, by default (without #define'ing a macro or passing an /arch:ETC
compiler flag), Wuffs does not use SIMD on MSVC x86_64.

Commit b64a7610 (after tag v0.4.0-alpha.4, before tag v0.4.0-alpha.5)
changed the default so that x86_64_v2 (roughly equivalent to SSE4.2) was
enabled by default, since the user from issue #148 was enabling that
anyway (in an unsupported way, by #define'ing a macro that was a private
implementation detail) with no problems (and better performance).

However, another user later reported (in issue #151) that enabling SIMD
on MSVC x86_64 somehow lead to ICEs (Internal Compiler Errors).

This commit restores the default to "no SIMD" and it is up to the MSVC
user to opt in to the SIMD code paths. Clang and GCC are unaffected:
SIMD remains enabled by default.

Updates #148
Updates #151