[bug#51863] [PATCH] gnu: webkitgtk: Really disable SSE2 on i686-linux.

[Diego Nicola Barbato]

Hey Guix,

Commit d82fd7c2dd542693988f61fb15c020e3209ac7ec (gnu: webkitgtk: Disable
SSE2 when not on x86_64.) on master breaks webkitgtk on i686-linux.

(I'm Cc-ing Leo, Liliana, and Mark since you were all involved in
upgrading webkitgtk to 2.34.1.)

The offending patch attempts to disable SSE2 by conditionally adding a
phase which removes the call to 'CHECK_FOR_SSE2' from the end of
'Source/cmake/DetectSSE2.cmake'.  This phase doesn't do anything about
'SSE2_SUPPORT_FOUND' being set to 'FALSE' at line 34 in the same file,
which causes the following snippet starting at line 152 in
'Source/cmake/WebKitCompilerFlags.cmake'

--8<---------------cut here---------------start------------->8---
    # Force SSE2 fp on x86 builds.
    if (WTF_CPU_X86 AND NOT CMAKE_CROSSCOMPILING)
        WEBKIT_PREPEND_GLOBAL_COMPILER_FLAGS(-msse2 -mfpmath=sse)
        include(DetectSSE2)
        if (NOT SSE2_SUPPORT_FOUND)
            message(FATAL_ERROR "SSE2 support is required to compile WebKit")
        endif ()
    endif ()
--8<---------------cut here---------------end--------------->8---

to fail with the following error when building for i686.

--8<---------------cut here---------------start------------->8---
CMake Error at Source/cmake/WebKitCompilerFlags.cmake:157 (message):
  SSE2 support is required to compile WebKit
--8<---------------cut here---------------end--------------->8---

The attached patch removes the code for adding the broken 'disable-sse2'
phase.  Instead it disables SSE2 using a patch from Debian and by
setting 'CFLAGS' and 'CXXFLAGS' to '-march=i686' in the
'prepare-build-environment' phase when building for i686.  The latter is
necessary because clang, unlike gcc, defaults to '-march=pentium4',
which enables SSE2.

With this patch I've successfully built webkitgtk and epiphany on
i686-linux and x86_64-linux.

Regards,

Diego

0001-gnu-webkitgtk-Really-disable-SSE2-on-i686-linux.patch
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