refactor(simd.h): Simplify vbool16 casting (#4105)

Some of the ways we were using unions for type punning in the vbool16
class were unnecessary, as both union members were basically the same
type. Simplify by getting rid of the unnecessary m_bits union member.

This also makes Sonar static analysis happier about these dubious uses
of unions for type punning.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

src/include/OpenImageIO/simd.h

@@ -920,10 +920,7 @@ class vbool16 {
 
 private:
     // The actual data representation
-    union {
-        simd_t   m_simd;
-        uint16_t m_bits;
-    };
+    simd_t m_simd;
 };
 
 
@@ -3920,19 +3917,15 @@ OIIO_FORCEINLINE bool none (const vbool8& v) { return reduce_or(v) == false; }
 
 OIIO_FORCEINLINE int vbool16::operator[] (int i) const {
     OIIO_DASSERT(i >= 0 && i < elements);
-#if OIIO_SIMD_AVX >= 512
-    return (int(m_simd) >> i) & 1;
-#else
-    return (m_bits >> i) & 1;
-#endif
+    return (static_cast<uint16_t>(m_simd) >> i) & 1;
 }
 
 OIIO_FORCEINLINE void vbool16::setcomp (int i, bool value) {
     OIIO_DASSERT(i >= 0 && i < elements);
-    int bits = m_bits;
+    int bits = static_cast<uint16_t>(m_simd);
     bits &= (0xffff ^ (1<<i));
     bits |= (int(value)<<i);
-    m_bits = bits;
+    m_simd = static_cast<simd_t>(bits);
 }
 
 
@@ -4015,11 +4008,7 @@ OIIO_FORCEINLINE const vbool16& vbool16::operator= (const vbool16 & other) {
 
 
 OIIO_FORCEINLINE int vbool16::bitmask () const {
-#if OIIO_SIMD_AVX >= 512
-    return int(m_simd);
-#else
-    return int(m_bits);
-#endif
+    return static_cast<int>(m_simd);
 }
 
 
@@ -4038,13 +4027,13 @@ OIIO_FORCEINLINE const vbool16 vbool16::True () {
 
 
 OIIO_FORCEINLINE void vbool16::store (bool *values) const {
-    SIMD_DO (values[i] = m_bits & (1<<i));
+    SIMD_DO (values[i] = m_simd & (1<<i));
 }
 
 OIIO_FORCEINLINE void vbool16::store (bool *values, int n) const {
     OIIO_DASSERT (n >= 0 && n <= elements);
     for (int i = 0; i < n; ++i)
-        values[i] = m_bits & (1<<i);
+        values[i] = m_simd & (1<<i);
 }
 
 
@@ -4070,31 +4059,31 @@ OIIO_FORCEINLINE vbool16 operator! (const vbool16 & a) {
 #if OIIO_SIMD_AVX >= 512
     return _mm512_knot (a.simd());
 #else
-    return vbool16 (a.m_bits ^ 0xffff);
+    return vbool16 (a.m_simd ^ 0xffff);
 #endif
 }
 
 OIIO_FORCEINLINE vbool16 operator& (const vbool16 & a, const vbool16 & b) {
 #if OIIO_SIMD_AVX >= 512
     return _mm512_kand (a.simd(), b.simd());
 #else
-    return vbool16 (a.m_bits & b.m_bits);
+    return vbool16 (a.m_simd & b.m_simd);
 #endif
 }
 
 OIIO_FORCEINLINE vbool16 operator| (const vbool16 & a, const vbool16 & b) {
 #if OIIO_SIMD_AVX >= 512
     return _mm512_kor (a.simd(), b.simd());
 #else
-    return vbool16 (a.m_bits | b.m_bits);
+    return vbool16 (a.m_simd | b.m_simd);
 #endif
 }
 
 OIIO_FORCEINLINE vbool16 operator^ (const vbool16& a, const vbool16& b) {
 #if OIIO_SIMD_AVX >= 512
     return _mm512_kxor (a.simd(), b.simd());
 #else
-    return vbool16 (a.m_bits ^ b.m_bits);
+    return vbool16 (a.m_simd ^ b.m_simd);
 #endif
 }
 
@@ -4121,15 +4110,15 @@ OIIO_FORCEINLINE vbool16 operator== (const vbool16 & a, const vbool16 & b) {
 #if OIIO_SIMD_AVX >= 512
     return _mm512_kxnor (a.simd(), b.simd());
 #else
-    return vbool16 (!(a.m_bits ^ b.m_bits));
+    return vbool16 (!(a.m_simd ^ b.m_simd));
 #endif
 }
 
 OIIO_FORCEINLINE vbool16 operator!= (const vbool16 & a, const vbool16 & b) {
 #if OIIO_SIMD_AVX >= 512
     return _mm512_kxor (a.simd(), b.simd());
 #else
-    return vbool16 (a.m_bits ^ b.m_bits);
+    return vbool16 (a.m_simd ^ b.m_simd);
 #endif
 }