meson: Fix runtime CPU detection with MSVCmeson

With GCC, Clang, ICC, etc, we differentiate between 'may support this
SIMD' and 'presume we have this SIMD' by checking whether the SIMD
/ intrinsics can be compiled by the compiler as-is (presume) or with
SIMD cflags (may have).

With MSVC, the compiler will always build SIMD/intrinsics targeting
all specific instruction sets supported by that version of the
compiler. No special arguments are ever needed. If runtime CPU
detection is not disabled, we must always assume that we only 'may
have' it.

1 files changed, 33 insertions, 16 deletions

diff --git a/meson.build b/meson.build
index ea90c713..65cb9424 100644
--- a/meson.build
+++ b/meson.build
@@ -184,6 +184,22 @@ if opt_custom_modes
 endif
 
 rtcd_support = []
+# With GCC, Clang, ICC, etc, we differentiate between 'may support this SIMD'
+# and 'presume we have this SIMD' by checking whether the SIMD / intrinsics can
+# be compiled by the compiler as-is (presume) or with SIMD cflags (may have).
+# With MSVC, the compiler will always build SIMD/intrinsics targeting all
+# specific instruction sets supported by that version of the compiler. No
+# special arguments are ever needed. If runtime CPU detection is not disabled,
+# we must always assume that we only 'may have' it.
+opus_can_presume_simd = true
+if cc.get_argument_syntax() == 'msvc'
+  if opt_rtcd.disabled()
+    warning('Building with an MSVC-like compiler and runtime CPU detection is disabled. Outputs may not run on all @0@ CPUs.'.format(host_cpu_family))
+  else
+    opus_can_presume_simd = false
+  endif
+endif
+
 opus_arm_external_asm = false
 
 asm_tmpl = '''
@@ -242,14 +258,14 @@ if not opt_asm.disabled()
       # only use them after runtime detection.
       # The same rules apply for x86 assembly and intrinsics.
 
-      opus_arm_presume_edsp = opus_conf.has('OPUS_ARM_INLINE_EDSP')
-      opus_arm_may_have_edsp = opus_arm_presume_edsp
+      opus_arm_may_have_edsp = opus_conf.has('OPUS_ARM_INLINE_EDSP')
+      opus_arm_presume_edsp = opus_arm_may_have_edsp and opus_can_presume_simd
 
-      opus_arm_presume_media = opus_conf.has('OPUS_ARM_INLINE_MEDIA')
-      opus_arm_may_have_media = opus_arm_presume_media
+      opus_arm_may_have_media = opus_conf.has('OPUS_ARM_INLINE_MEDIA')
+      opus_arm_presume_media = opus_arm_may_have_media and opus_can_presume_simd
 
-      opus_arm_presume_neon = opus_conf.has('OPUS_ARM_INLINE_NEON')
-      opus_arm_may_have_neon = opus_arm_presume_neon
+      opus_arm_may_have_neon = opus_conf.has('OPUS_ARM_INLINE_NEON')
+      opus_arm_presume_neon = opus_arm_may_have_neon and opus_can_presume_simd
 
       if not opt_rtcd.disabled()
         if not opus_arm_may_have_edsp
@@ -344,7 +360,7 @@ if not opt_intrinsics.disabled()
     intrin_name = 'ARMv7/AArch64 NEON'
     if cc.links(intrin_check,
                 name: 'compiler supports @0@ intrinsics'.format(intrin_name))
-      opus_arm_presume_neon_intr = true
+      opus_arm_presume_neon_intr = opus_can_presume_simd
       opus_arm_may_have_neon_intr = true
     else
       opus_arm_presume_neon_intr = false
@@ -382,7 +398,7 @@ if not opt_intrinsics.disabled()
     intrin_name = 'AArch64 NEON'
     if cc.links(intrin_check,
                 name: 'compiler supports @0@ intrinsics'.format(intrin_name))
-      opus_arm_presume_aarch64_neon_intr = true
+      opus_arm_presume_aarch64_neon_intr = opus_can_presume_simd
       opus_arm_may_have_aarch64_neon_intr = true
     else
       opus_arm_presume_aarch64_neon_intr = false
@@ -407,10 +423,10 @@ if not opt_intrinsics.disabled()
   elif host_cpu_family in ['x86', 'x86_64']
     # XXX: allow external override/specification of the flags
     x86_intrinsics = [
-      [ 'SSE', 'xmmintrin.h', '__m128', '_mm_setzero_ps()', '-msse' ],
-      [ 'SSE2', 'emmintrin.h', '__m128i', '_mm_setzero_si128()', '-msse2' ],
-      [ 'SSE4.1', 'smmintrin.h', '__m128i', '_mm_setzero_si128(); mtest = _mm_cmpeq_epi64(mtest, mtest)', '-msse4.1' ],
-      [ 'AVX', 'immintrin.h', '__m256', '_mm256_setzero_ps()', '-mavx' ],
+      [ 'SSE', 'xmmintrin.h', '__m128', '_mm_setzero_ps()', ['-msse'] ],
+      [ 'SSE2', 'emmintrin.h', '__m128i', '_mm_setzero_si128()', ['-msse2'] ],
+      [ 'SSE4.1', 'smmintrin.h', '__m128i', '_mm_setzero_si128(); mtest = _mm_cmpeq_epi64(mtest, mtest)', ['-msse4.1'] ],
+      [ 'AVX', 'immintrin.h', '__m256', '_mm256_setzero_ps()', ['-mavx'] ],
     ]
 
     foreach intrin : x86_intrinsics
@@ -421,15 +437,16 @@ if not opt_intrinsics.disabled()
                           return *((unsigned char *) &mtest) != 0;
                         }'''.format(intrin[1],intrin[2],intrin[3])
       intrin_name = intrin[0]
-      intrin_args = intrin[4]
+      # Intrinsics arguments are not available with MSVC-like compilers
+      intrin_args = cc.get_argument_syntax() == 'msvc' ? [] : intrin[4]
       if cc.links(intrin_check, name : 'compiler supports @0@ intrinsics'.format(intrin_name))
         may_have_intrin = true
-        presume_intrin = true
-      else
+        presume_intrin = opus_can_presume_simd
+      elif intrin_args.length() > 0
         presume_intrin = false
         if cc.links(intrin_check,
                     args : intrin_args,
-                    name : 'compiler supports @0@ intrinsics with @1@'.format(intrin_name, intrin_args))
+                    name : 'compiler supports @0@ intrinsics with @1@'.format(intrin_name, ' '.join(intrin_args)))
           may_have_intrin = true
         else
           may_have_intrin = false