arm, neon: neon/fma support for glm_mat2_mul()

include/cglm/simd/neon/mat2.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c), Recep Aslantas.
+ *
+ * MIT License (MIT), http://opensource.org/licenses/MIT
+ * Full license can be found in the LICENSE file
+ */
+
+#ifndef cglm_mat2_neon_h
+#define cglm_mat2_neon_h
+#if defined(__ARM_NEON_FP)
+
+#include "../../common.h"
+#include "../intrin.h"
+
+CGLM_INLINE
+void
+glm_mat2_mul_neon(mat2 m1, mat2 m2, mat2 dest) {
+  float32x4x2_t a1;
+  glmm_128 x0,  x1, x2;
+  float32x2_t   dc, ba;
+
+  x1 = glmm_load(m1[0]); /* d c b a */
+  x2 = glmm_load(m2[0]); /* h g f e */
+  
+  dc  = vget_high_f32(x1);
+  ba  = vget_low_f32(x1);
+
+  /* g g e e, h h f f */
+  a1 = vtrnq_f32(x2, x2);
+  
+  /*
+   dest[0][0] = a * e + c * f;
+   dest[0][1] = b * e + d * f;
+   dest[1][0] = a * g + c * h;
+   dest[1][1] = b * g + d * h;
+   */
+  x0 = glmm_fmadd(vcombine_f32(ba, ba), a1.val[0],
+                  vmulq_f32(vcombine_f32(dc, dc), a1.val[1]));
+
+  glmm_store(dest[0], x0);
+}
+
+#endif
+#endif /* cglm_mat2_neon_h */