Disabled optimized amaxv kernels.

Details:
- Disabled use of optimized amaxv kernels, which use vector intrinsics
  for both 's' and 'd' datatypes. We disable these kernels because the
  current implementations fail to observe a semantic property of the
  BLAS i?amax_() subroutine, which is to return the index of the
  *first* element containing the maximum absolute value (that is, the
  first element if there exist two or more elements that contain the
  same value). With the optimized kernels disabled, the affected
  subconfigurations (haswell, zen, zen2, knl, and skx) will use the
  default reference implementations. Thanks to Mat Cross for reporting
  this issue via #380.
- CREDITS file update.

CREDITS

@@ -18,6 +18,7 @@ but many others have contributed code and feedback, including
   Matthew Brett            @matthew-brett      (University of Birmingham)
   Jed Brown                @jedbrown           (Argonne National Laboratory)
   Robin Christ             @robinchrist
+  Mat Cross                @matcross           (NAG)
   Kay Dewhurst             @jkd2016            (Max Planck Institute, Halle, Germany)
   Jeff Diamond                                 (Oracle)
   Johannes Dieterich       @iotamudelta

config/haswell/bli_cntx_init_haswell.c

@@ -89,10 +89,14 @@ void bli_cntx_init_haswell( cntx_t* cntx )
 	// Update the context with optimized level-1v kernels.
 	bli_cntx_set_l1v_kers
 	(
-	  10,
+	  8,
+#if 0
+	  // NOTE: Disabled vectorized amaxv kernels due to incorrect semantics.
+	  // See issue #380 for more details.
 	  // amaxv
 	  BLIS_AMAXV_KER,  BLIS_FLOAT,  bli_samaxv_zen_int,
 	  BLIS_AMAXV_KER,  BLIS_DOUBLE, bli_damaxv_zen_int,
+#endif
 	  // axpyv
 #if 0
 	  BLIS_AXPYV_KER,  BLIS_FLOAT,  bli_saxpyv_zen_int,

config/knl/bli_cntx_init_knl.c

@@ -78,10 +78,14 @@ void bli_cntx_init_knl( cntx_t* cntx )
 	// Update the context with optimized level-1v kernels.
 	bli_cntx_set_l1v_kers
 	(
-	  10,
+	  8,
+#if 0
+	  // NOTE: Disabled vectorized amaxv kernels due to incorrect semantics.
+	  // See issue #380 for more details.
 	  // amaxv
 	  BLIS_AMAXV_KER,  BLIS_FLOAT,  bli_samaxv_zen_int,
 	  BLIS_AMAXV_KER,  BLIS_DOUBLE, bli_damaxv_zen_int,
+#endif
 	  // axpyv
 #if 0
 	  BLIS_AXPYV_KER,  BLIS_FLOAT,  bli_saxpyv_zen_int,

config/old/haswellbb/bli_cntx_init_haswell.c

@@ -149,10 +149,14 @@ void bli_cntx_init_haswell( cntx_t* cntx )
 	// Update the context with optimized level-1v kernels.
 	bli_cntx_set_l1v_kers
 	(
-	  10,
+	  8,
+#if 0
+	  // NOTE: Disabled vectorized amaxv kernels due to incorrect semantics.
+	  // See issue #380 for more details.
 	  // amaxv
 	  BLIS_AMAXV_KER,  BLIS_FLOAT,  bli_samaxv_zen_int,
 	  BLIS_AMAXV_KER,  BLIS_DOUBLE, bli_damaxv_zen_int,
+#endif
 	  // axpyv
 #if 0
 	  BLIS_AXPYV_KER,  BLIS_FLOAT,  bli_saxpyv_zen_int,

config/skx/bli_cntx_init_skx.c

@@ -70,10 +70,14 @@ void bli_cntx_init_skx( cntx_t* cntx )
 	// Update the context with optimized level-1v kernels.
 	bli_cntx_set_l1v_kers
 	(
-	  10,
+	  8,
+#if 0
+	  // NOTE: Disabled vectorized amaxv kernels due to incorrect semantics.
+	  // See issue #380 for more details.
 	  // amaxv
 	  BLIS_AMAXV_KER,  BLIS_FLOAT,  bli_samaxv_zen_int,
 	  BLIS_AMAXV_KER,  BLIS_DOUBLE, bli_damaxv_zen_int,
+#endif
 	  // axpyv
 #if 0
 	  BLIS_AXPYV_KER,  BLIS_FLOAT,  bli_saxpyv_zen_int,

config/zen/bli_cntx_init_zen.c

@@ -82,10 +82,14 @@ void bli_cntx_init_zen( cntx_t* cntx )
 	// Update the context with optimized level-1v kernels.
 	bli_cntx_set_l1v_kers
 	(
-	  10,
+	  8,
+#if 0
+	  // NOTE: Disabled vectorized amaxv kernels due to incorrect semantics.
+	  // See issue #380 for more details.
 	  // amaxv
 	  BLIS_AMAXV_KER,  BLIS_FLOAT,  bli_samaxv_zen_int,
 	  BLIS_AMAXV_KER,  BLIS_DOUBLE, bli_damaxv_zen_int,
+#endif
 	  // axpyv
 #if 0
 	  BLIS_AXPYV_KER,  BLIS_FLOAT,  bli_saxpyv_zen_int,

config/zen2/bli_cntx_init_zen2.c

@@ -79,10 +79,14 @@ void bli_cntx_init_zen2( cntx_t* cntx )
 	// Update the context with optimized level-1v kernels.
 	bli_cntx_set_l1v_kers
 	(
-	  10,
+	  8,
+#if 0
+	  // NOTE: Disabled vectorized amaxv kernels due to incorrect semantics.
+	  // See issue #380 for more details.
 	  // amaxv
 	  BLIS_AMAXV_KER,  BLIS_FLOAT,  bli_samaxv_zen_int,
 	  BLIS_AMAXV_KER,  BLIS_DOUBLE, bli_damaxv_zen_int,
+#endif
 	  // axpyv
 
 	  BLIS_AXPYV_KER,  BLIS_FLOAT,  bli_saxpyv_zen_int10,