Trying to use fma instructions when possible

Compilers sometimes replace vmlaq*() with fmul+fadd instead of fmla.
Trying to use vfmaq*() instead when possible.

celt/arm/celt_neon_intr.c

@@ -97,6 +97,14 @@ void xcorr_kernel_neon_fixed(const opus_val16 * x, const opus_val16 * y, opus_va
 }
 
 #else
+
+#if defined(__ARM_FEATURE_FMA) && defined(__ARM_ARCH_ISA_A64)
+/* If we can, force the compiler to use an FMA instruction rather than break
+ *    vmlaq_f32() into fmul/fadd. */
+#define vmlaq_lane_f32(a,b,c,lane) vfmaq_lane_f32(a,b,c,lane)
+#endif
+
+
 /*
  * Function: xcorr_kernel_neon_float
  * ---------------------------------

celt/arm/pitch_neon_intr.c

@@ -130,6 +130,13 @@ void dual_inner_prod_neon(const opus_val16 *x, const opus_val16 *y01, const opus
 
 /* ========================================================================== */
 
+#ifdef __ARM_FEATURE_FMA
+/* If we can, force the compiler to use an FMA instruction rather than break
+   vmlaq_f32() into fmul/fadd. */
+#define vmlaq_f32(a,b,c) vfmaq_f32(a,b,c)
+#endif
+
+
 #ifdef OPUS_CHECK_ASM
 
 /* This part of code simulates floating-point NEON operations. */

dnn/vec_neon.h

@@ -49,6 +49,12 @@ static OPUS_INLINE int16x8_t vmull_high_s8(int8x16_t a, int8x16_t b) {
 }
 #endif
 
+#ifdef __ARM_FEATURE_FMA
+/* If we can, force the compiler to use an FMA instruction rather than break
+   vmlaq_f32() into fmul/fadd. */
+#define vmlaq_f32(a,b,c) vfmaq_f32(a,b,c)
+#endif
+
 #ifndef LPCNET_TEST
 static inline float32x4_t exp4_approx(float32x4_t x) {
   int32x4_t i;