meson.build: Use SSE math for MinGW X86 build as per sse2 option

This patch adds missing compiler flags to build 32bit driver. It helps to build 32bit
using mingw successfully

Generated GL driver is tested using piglit, glretrace, conform and
some opengl apps

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7806>

meson.build

@@ -1129,6 +1129,21 @@ if host_machine.system() == 'windows'
   endif
 endif
 
+if get_option('sse2') and host_machine.system() == 'windows' and host_machine.cpu_family() == 'x86' and cc.get_id() == 'gcc'
+  # These settings make generated MinGW code match MSVC and follow
+  # GCC advice on https://gcc.gnu.org/wiki/FloatingPointMath#x86note
+  #
+  # NOTE: We need to ensure stack is realigned given that we
+  # produce shared objects, and have no control over the stack
+  # alignment policy of the application. Therefore we need
+  # -mstackrealign or -mincoming-stack-boundary=2.
+  #
+  # XXX: We could have SSE without -mstackrealign if we always used
+  # __attribute__((force_align_arg_pointer)), but that's not
+  # always the case.
+  c_args += ['-msse', '-msse2', '-mfpmath=sse', '-mstackrealign']
+endif
+
 if host_machine.cpu_family().startswith('x86') and cc.get_id() != 'msvc'
   pre_args += '-DUSE_SSE41'
   with_sse41 = true

meson_options.txt

@@ -441,3 +441,9 @@ option(
   value : 'auto',
   description : 'Use ZSTD instead of ZLIB in some cases.'
 )
+option(
+  'sse2',
+  type : 'boolean',
+  value : true,
+  description : 'use msse2 flag for mingw x86. Default: true',
+)