Math: Optimise 16-bit matrix multiplication functions.

src/math/matrix.c

@@ -3,93 +3,138 @@
 // Copyright(c) 2022 Intel Corporation. All rights reserved.
 //
 // Author: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
+//	   Shriram Shastry <malladi.sastry@linux.intel.com>
+//
 
 #include <sof/math/matrix.h>
 #include <errno.h>
 #include <stdint.h>
 
+/**
+ * Description: Performs matrix multiplication of two fixed-point 16-bit integer matrices,
+ *	 storing the result in a third matrix. It accounts for fractional bits for
+ *	 fixed-point arithmetic, adjusting the result accordingly.
+ *
+ * Arguments:
+ *   a: pointer to the first input matrix
+ *   b: pointer to the second input matrix
+ *   c: pointer to the output matrix to store result
+ *
+ * Return:
+ *   0 on successful multiplication.
+ *   -EINVAL if input dimensions do not allow for multiplication.
+ *   -ERANGE if the shift operation might cause integer overflow.
+ */
 int mat_multiply(struct mat_matrix_16b *a, struct mat_matrix_16b *b, struct mat_matrix_16b *c)
 {
-	int64_t s;
-	int16_t *x;
-	int16_t *y;
-	int16_t *z = c->data;
-	int i, j, k;
-	int y_inc = b->columns;
-	const int shift_minus_one = a->fractions + b->fractions - c->fractions - 1;
-
+	/* Validate matrix dimensions are compatible for multiplication */
 	if (a->columns != b->rows || a->rows != c->rows || b->columns != c->columns)
 		return -EINVAL;
 
-	/* If all data is Q0 */
-	if (shift_minus_one == -1) {
+	int32_t acc;	/* Accumulator for dot product calculation */
+	int16_t *x, *y, *z = c->data; /* Pointers for matrices a, b, and c */
+	int i, j, k;	/* Loop counters */
+	int y_inc = b->columns;	   /* Column increment for matrix b elements */
+	/* Calculate shift amount for adjusting fractional bits in the result */
+	const int shift = a->fractions + b->fractions - c->fractions - 1;
+
+	/* Check shift to ensure no integer overflow occurs during shifting */
+	if (shift < -1 || shift > 31)
+		return -ERANGE;
+
+	/* Special case when shift is -1 (Q0 data) */
+	if (shift == -1) {
+		/* Matrix multiplication loop */
 		for (i = 0; i < a->rows; i++) {
 			for (j = 0; j < b->columns; j++) {
-				s = 0;
+				/* Initialize accumulator for each element */
+				acc = 0;
+				/* Set x at the start of ith row of a */
 				x = a->data + a->columns * i;
+				/* Set y at the top of jth column of b */
 				y = b->data + j;
+				/* Dot product loop */
 				for (k = 0; k < b->rows; k++) {
-					s += (int32_t)(*x) * (*y);
-					x++;
+					/* Multiply & accumulate */
+					acc += (int32_t)(*x++) * (*y);
+					 /* Move to next row in the current column of b */
 					y += y_inc;
 				}
-				*z = (int16_t)s; /* For Q16.0 */
-				z++;
+				/* Enhanced pointer arithmetic */
+				*z = (int16_t)acc;
+				z++; /* Move to the next element in the output matrix */
 			}
 		}
-
-		return 0;
-	}
-
-	for (i = 0; i < a->rows; i++) {
-		for (j = 0; j < b->columns; j++) {
-			s = 0;
-			x = a->data + a->columns * i;
-			y = b->data + j;
-			for (k = 0; k < b->rows; k++) {
-				s += (int32_t)(*x) * (*y);
-				x++;
-				y += y_inc;
+	} else {
+		/* General case for other shift values */
+		for (i = 0; i < a->rows; i++) {
+			for (j = 0; j < b->columns; j++) {
+				/* Initialize accumulator for each element */
+				acc = 0;
+				/* Set x at the start of ith row of a */
+				x = a->data + a->columns * i;
+				/* Set y at the top of jth column of b */
+				y = b->data + j;
+				/* Dot product loop */
+				for (k = 0; k < b->rows; k++) {
+					/* Multiply & accumulate Enhanced pointer arithmetic */
+					acc += (int32_t)(*x++) * (*y);
+					/* Move to next row in the current column of b */
+					y += y_inc;
+				}
+				/* Enhanced pointer arithmetic */
+				*z = (int16_t)(((acc >> shift) + 1) >> 1); /*Shift to Qx.y */
+				z++; /* Move to the next element in the output matrix */
 			}
-			*z = (int16_t)(((s >> shift_minus_one) + 1) >> 1); /*Shift to Qx.y */
-			z++;
 		}
 	}
 	return 0;
 }
 
+/**
+ * Description: Performs element-wise multiplication of two matrices with 16-bit integer elements
+ *		and stores the result in a third matrix. Checks that all matrices have the same
+ *		dimensions and adjusts for fractional bits appropriately. This operation handles
+ *		the manipulation of fixed-point precision based on the fractional bits present in
+ *		the matrices.
+ *
+ * Arguments:
+ *   a - pointer to the first input matrix
+ *   b - pointer to the second input matrix
+ *   c - pointer to the output matrix where the result will be stored
+ *
+ * Returns:
+ *   0 on successful multiplication,
+ *  -EINVAL if input pointers are NULL or matrix dimensions do not match.
+ */
 int mat_multiply_elementwise(struct mat_matrix_16b *a, struct mat_matrix_16b *b,
 			     struct mat_matrix_16b *c)
-{	int64_t p;
+{
+	/* Validate matrix dimensions and non-null pointers */
+	if (!a || !b || !c ||
+	    a->columns != b->columns || a->rows != b->rows ||
+	    c->columns != a->columns || c->rows != a->rows) {
+		return -EINVAL;
+	}
+
 	int16_t *x = a->data;
 	int16_t *y = b->data;
 	int16_t *z = c->data;
+	int32_t p;
 	int i;
 	const int shift_minus_one = a->fractions + b->fractions - c->fractions - 1;
 
-	if (a->columns != b->columns || b->columns != c->columns ||
-	    a->rows != b->rows || b->rows != c->rows) {
-		return -EINVAL;
-	}
-
 	/* If all data is Q0 */
 	if (shift_minus_one == -1) {
-		for (i = 0; i < a->rows * a->columns; i++) {
+		for (i = 0; i < a->rows * a->columns; i++, x++, y++, z++)
 			*z = *x * *y;
-			x++;
-			y++;
-			z++;
-		}
 
 		return 0;
 	}
 
-	for (i = 0; i < a->rows * a->columns; i++) {
+	for (i = 0; i < a->rows * a->columns; i++, x++, y++, z++) {
 		p = (int32_t)(*x) * *y;
-		*z = (int16_t)(((p >> shift_minus_one) + 1) >> 1); /*Shift to Qx.y */
-		x++;
-		y++;
-		z++;
+		*z = (int16_t)(((p >> shift_minus_one) + 1) >> 1); /* Shift to Qx.y */
 	}
 
 	return 0;