[Opus] Update to v1.2.1

third_party/opus/src/silk/fixed/k2a_Q16_FIX.c

Index: third_party/opus/src/silk/fixed/k2a_Q16_FIX.c
diff --git a/third_party/opus/src/silk/fixed/k2a_Q16_FIX.c b/third_party/opus/src/silk/fixed/k2a_Q16_FIX.c
index 3b039875446a13886a9b22ea1e2b0f54c2062a05..1595aa62126625750705b5d47b42bdc586f05942 100644
--- a/third_party/opus/src/silk/fixed/k2a_Q16_FIX.c
+++ b/third_party/opus/src/silk/fixed/k2a_Q16_FIX.c
@@ -39,15 +39,16 @@ void silk_k2a_Q16(
 )
 {
     opus_int   k, n;
-    opus_int32 Atmp[ SILK_MAX_ORDER_LPC ];
+    opus_int32 rc, tmp1, tmp2;
 
     for( k = 0; k < order; k++ ) {
-        for( n = 0; n < k; n++ ) {
-            Atmp[ n ] = A_Q24[ n ];
+        rc = rc_Q16[ k ];
+        for( n = 0; n < (k + 1) >> 1; n++ ) {
+            tmp1 = A_Q24[ n ];
+            tmp2 = A_Q24[ k - n - 1 ];
+            A_Q24[ n ]         = silk_SMLAWW( tmp1, tmp2, rc );
+            A_Q24[ k - n - 1 ] = silk_SMLAWW( tmp2, tmp1, rc );
         }
-        for( n = 0; n < k; n++ ) {
-            A_Q24[ n ] = silk_SMLAWW( A_Q24[ n ], Atmp[ k - n - 1 ], rc_Q16[ k ] );
-        }
-        A_Q24[ k ] = -silk_LSHIFT( rc_Q16[ k ], 8 );
+        A_Q24[ k ] = -silk_LSHIFT( rc, 8 );
     }
 }