Replace naive omatcopy_rt with 4x4 blocked implementation

as suggested by MigMuc in issue 2532

kernel/arm/omatcopy_rt.c

@@ -1,5 +1,5 @@
 /***************************************************************************
-Copyright (c) 2013, The OpenBLAS Project
+Copyright (c) 2021, The OpenBLAS Project
 All rights reserved.
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
@@ -27,36 +27,208 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "common.h"
 
-/*****************************************************
- * 2014/06/09 Saar
- *
- * Order rowMajor
- * Trans
- *
-******************************************************/
-
 int CNAME(BLASLONG rows, BLASLONG cols, FLOAT alpha, FLOAT *a, BLASLONG lda, FLOAT *b, BLASLONG ldb)
-{
-	BLASLONG i,j;
-	FLOAT *aptr,*bptr;
 
-	if ( rows <= 0     )  return(0);
-	if ( cols <= 0     )  return(0);
+    BLASLONG i, j;
+    FLOAT *a_offset, *a_offset1, *a_offset2, *a_offset3, *a_offset4;
+    FLOAT *b_offset, *b_offset1, *b_offset2, *b_offset3, *b_offset4;
 
-	aptr = a;
+    if (rows <= 0)  return 0;
+    if (cols <= 0)  return 0;
 
-	for ( i=0; i<rows ; i++ )
-	{
-		bptr = &b[i];
-		for(j=0; j<cols; j++)
-		{
-			bptr[j*ldb] = alpha * aptr[j];
-		}
-		aptr += lda;
-	}
+    a_offset = a;
+    b_offset = b;
 
-	return(0);
+    i = (rows >> 2);
+    if (i > 0) {
+        do {
+            a_offset1 = a_offset;
+            a_offset2 = a_offset1 + lda;
+            a_offset3 = a_offset2 + lda;
+            a_offset4 = a_offset3 + lda;
+            a_offset += 4 * lda;
+
+            b_offset1 = b_offset;
+            b_offset2 = b_offset1 + ldb;
+            b_offset3 = b_offset2 + ldb;
+            b_offset4 = b_offset3 + ldb;
+            b_offset += 4;
+
+            j = (cols >> 2);
+            if (j > 0) {
+                do {
+                /* Column 1 of MAT_B */
+                *(b_offset1 + 0) = *(a_offset1 + 0)*alpha; // Row 1 of MAT_A
+                *(b_offset2 + 0) = *(a_offset1 + 1)*alpha;
+                *(b_offset3 + 0) = *(a_offset1 + 2)*alpha;
+                *(b_offset4 + 0) = *(a_offset1 + 3)*alpha;
+
+                /* Column 2 of MAT_B */
+                *(b_offset1 + 1) = *(a_offset2 + 0)*alpha; // Row 2 of MAT_A
+                *(b_offset2 + 1) = *(a_offset2 + 1)*alpha;
+                *(b_offset3 + 1) = *(a_offset2 + 2)*alpha;
+                *(b_offset4 + 1) = *(a_offset2 + 3)*alpha;
+
+                /* Column 3 of MAT_B */
+                *(b_offset1 + 2) = *(a_offset3 + 0)*alpha; // Row 3 of MAT_A
+                *(b_offset2 + 2) = *(a_offset3 + 1)*alpha;
+                *(b_offset3 + 2) = *(a_offset3 + 2)*alpha;
+                *(b_offset4 + 2) = *(a_offset3 + 3)*alpha;
+
+                /* Column 4 of MAT_B */
+                *(b_offset1 + 3) = *(a_offset4 + 0)*alpha; // Row 4 of MAT_A
+                *(b_offset2 + 3) = *(a_offset4 + 1)*alpha;
+                *(b_offset3 + 3) = *(a_offset4 + 2)*alpha;
+                *(b_offset4 + 3) = *(a_offset4 + 3)*alpha;
+
+                a_offset1 += 4;
+                a_offset2 += 4;
+                a_offset3 += 4;
+                a_offset4 += 4;
+                b_offset1 += ldb * 4;
+                b_offset2 += ldb * 4;
+                b_offset3 += ldb * 4;
+                b_offset4 += ldb * 4;
+                
+                j--;
+                } while (j > 0);
+            } // if(j > 0)
+
+
+            if (cols & 2) {
+                *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+                *(b_offset2 + 0) = *(a_offset1 + 1)*alpha;
+
+                *(b_offset1 + 1) = *(a_offset2 + 0)*alpha;
+                *(b_offset2 + 1) = *(a_offset2 + 1)*alpha;
+
+                *(b_offset1 + 2) = *(a_offset3 + 0)*alpha;
+                *(b_offset2 + 2) = *(a_offset3 + 1)*alpha;
+
+                *(b_offset1 + 3) = *(a_offset4 + 0)*alpha;
+                *(b_offset2 + 3) = *(a_offset4 + 1)*alpha;
+
+                a_offset1 += 2;
+                a_offset2 += 2;
+                a_offset3 += 2;
+                a_offset4 += 2;
+
+                b_offset1 += ldb*2;
+
+            }
+
+            if (cols & 1) {
+                *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+
+                *(b_offset1 + 1) = *(a_offset2 + 0)*alpha;
+
+                *(b_offset1 + 2) = *(a_offset3 + 0)*alpha;
+
+                *(b_offset1 + 3) = *(a_offset4 + 0)*alpha;
+            }
+
+            i--;
+        } while (i > 0);
+    }
 
-}
 
+    if (rows & 2) {
+        a_offset1 = a_offset;
+        a_offset2 = a_offset1 + lda;
+        a_offset += 2 * lda;
+
+        b_offset1 = b_offset;
+        b_offset2 = b_offset1 + ldb;
+        b_offset3 = b_offset2 + ldb;
+        b_offset4 = b_offset3 + ldb;
+        b_offset += 2;
+
+        j = (cols >> 2);
+        if (j > 0){
+            do {
+                *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+                *(b_offset2 + 0) = *(a_offset1 + 1)*alpha;
+                *(b_offset3 + 0) = *(a_offset1 + 2)*alpha;
+                *(b_offset4 + 0) = *(a_offset1 + 3)*alpha;
+
+                *(b_offset1 + 1) = *(a_offset2 + 0)*alpha;
+                *(b_offset2 + 1) = *(a_offset2 + 1)*alpha;
+                *(b_offset3 + 1) = *(a_offset2 + 2)*alpha;
+                *(b_offset4 + 1) = *(a_offset2 + 3)*alpha;
+                
+                a_offset1 += 4;
+                a_offset2 += 4;
+                b_offset1 += ldb * 4;
+                b_offset2 += ldb * 4;
+                b_offset3 += ldb * 4;
+                b_offset4 += ldb * 4;
+
+                j--;
+            } while (j > 0);
+        }
+
+
+        if (cols & 2){
+            *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+            *(b_offset2 + 0) = *(a_offset1 + 1)*alpha;
+
+            *(b_offset1 + 1) = *(a_offset2 + 0)*alpha;
+            *(b_offset2 + 1) = *(a_offset2 + 1)*alpha;
+
+            a_offset1 += 2;
+            a_offset2 += 2;
+            b_offset1 += ldb*2;
+
+        }
+
+
+        if (cols & 1){
+            *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+            *(b_offset1 + 1) = *(a_offset2 + 0)*alpha;
+        }
+    } // if (rows & 2)
+
+
+    if (rows & 1) {
+        a_offset1 = a_offset;
+        a_offset += lda;
+
+        b_offset1 = b_offset;
+        b_offset2 = b_offset1 + ldb;
+        b_offset3 = b_offset2 + ldb;
+        b_offset4 = b_offset3 + ldb;
+
+        j = (cols >> 2);
+        if (j > 0){
+            do {
+                *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+                *(b_offset2 + 0) = *(a_offset1 + 1)*alpha;
+                *(b_offset3 + 0) = *(a_offset1 + 2)*alpha;
+                *(b_offset4 + 0) = *(a_offset1 + 3)*alpha;
+                
+                a_offset1 += 4;
+                b_offset1 += ldb * 4;
+                b_offset2 += ldb * 4;
+                b_offset3 += ldb * 4;
+                b_offset4 += ldb * 4;
+                
+                j--;
+            } while (j > 0);
+        }
+
+        if (cols & 2){
+            *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+            *(b_offset2 + 0) = *(a_offset1 + 1)*alpha;
+
+            a_offset1 += 2;
+            b_offset1 += ldb * 2;
+        }
+
+        if (cols & 1){
+            *(b_offset1 + 0) = *(a_offset1 + 0)*alpha;
+        }
+    }
+
+    return 0;
+}