fix(simd.h): Address NEON issues (#4143)

Primarily, recent changes (PR #4071) to vint4::store for the NEON case
appear to have some type mismatches, which apple clang on ARM-based Mac
(including our CI) seems ok with, but which is generating type errors on
other ARM Linux platforms.

I think the types were weird here, so I tightened it up to get the types
right for temporary variables in that function. That's the primary fix
here.

Secondarily, I modified simd.h and the CMake setup so that build option
USE_SIMD=0 will disable NEON in the same way that it disables SSE. (I
realized that USE_SIMD=0 was not disabling NEON, so there was no way for
a NEON platform to completely disable SIMD if they needed to.)

Fixes #4111

Signed-off-by: Larry Gritz <[email protected]>

Author: lgritz

src/cmake/compiler.cmake

@@ -303,7 +303,7 @@ set (SIMD_COMPILE_FLAGS "")
 if (NOT USE_SIMD STREQUAL "")
     message (STATUS "Compiling with SIMD level ${USE_SIMD}")
     if (USE_SIMD STREQUAL "0")
-        set (SIMD_COMPILE_FLAGS ${SIMD_COMPILE_FLAGS} "-DOIIO_NO_SSE=1")
+        set (SIMD_COMPILE_FLAGS ${SIMD_COMPILE_FLAGS} "-DOIIO_NO_SIMD=1")
     else ()
         string (REPLACE "," ";" SIMD_FEATURE_LIST ${USE_SIMD})
         foreach (feature ${SIMD_FEATURE_LIST})

src/include/OpenImageIO/simd.h

@@ -77,6 +77,13 @@
 // OIIO_SIMD_HAS_SIMD8 : nonzero if vfloat8, vint8, vbool8 are defined
 // OIIO_SIMD_HAS_SIMD16 : nonzero if vfloat16, vint16, vbool16 are defined
 
+#ifdef OIIO_NO_SIMD /* Request to disable all SIMD */
+#  define OIIO_NO_SSE 1
+#  define OIIO_NO_AVX 1
+#  define OIIO_NO_AVX2 1
+#  define OIIO_NO_NEON 1
+#endif
+
 #if defined(_M_ARM64) || defined(__aarch64__) || defined(__aarch64)
 #  ifndef __ARM_NEON__
 #      define __ARM_NEON__
@@ -4788,9 +4795,9 @@ OIIO_FORCEINLINE void vint4::store (unsigned char *values) const {
     _mm_store_ss((float*)values, _mm_castsi128_ps(val8));
 #elif OIIO_SIMD_NEON
     vint4 clamped = m_simd & vint4(0xff);
-    simd_t val16 = vcombine_s16(vqmovn_s32(clamped), vdup_n_s16(0));
-    simd_t val8 = vcombine_u8(vqmovun_s16(val16), vdup_n_u8(0));
-    vst1q_lane_u32((uint32_t*)values, val8, 0);
+    int16x8_t val16 = vcombine_s16(vqmovn_s32(clamped), vdup_n_s16(0));
+    uint8x16_t val8 = vcombine_u8(vqmovun_s16(val16), vdup_n_u8(0));
+    vst1q_lane_u32((uint32_t*)values, vreinterpretq_u32_u8(val8), 0);
 #else
     SIMD_DO (values[i] = m_val[i]);
 #endif