From c8eaf3ae2d19a60039f55e5579c44329ff2d3000 Mon Sep 17 00:00:00 2001
From: wernsaar <wernsaar@googlemail.com>
Date: Sat, 6 Sep 2014 19:41:57 +0200
Subject: [PATCH] optimized sgemv_t_4 kernel for very small sizes

---
 kernel/x86_64/sgemv_t_4.c | 98 +++++++++++++++++++++++++++++++++------
 1 file changed, 84 insertions(+), 14 deletions(-)

diff --git a/kernel/x86_64/sgemv_t_4.c b/kernel/x86_64/sgemv_t_4.c
index e4476080a..692dd536d 100644
--- a/kernel/x86_64/sgemv_t_4.c
+++ b/kernel/x86_64/sgemv_t_4.c
@@ -423,14 +423,37 @@ int CNAME(BLASLONG m, BLASLONG n, BLASLONG dummy1, FLOAT alpha, FLOAT *a, BLASLO
 
 		FLOAT *aj = a_ptr;
 		y_ptr = y;
-		for ( j=0; j<n; j++ )
+
+		if ( lda == 3 && inc_y == 1 )
 		{
-			*y_ptr += *aj * xtemp0 + *(aj+1) * xtemp1 + *(aj+2) *xtemp2;
-			 y_ptr += inc_y;
-			 aj    += lda;
+
+			for ( j=0; j< ( n & -4) ; j+=4 )
+			{
+
+				y_ptr[j]   += aj[0] * xtemp0 + aj[1]  * xtemp1 + aj[2]  * xtemp2;
+				y_ptr[j+1] += aj[3] * xtemp0 + aj[4]  * xtemp1 + aj[5]  * xtemp2;
+				y_ptr[j+2] += aj[6] * xtemp0 + aj[7]  * xtemp1 + aj[8]  * xtemp2;
+				y_ptr[j+3] += aj[9] * xtemp0 + aj[10] * xtemp1 + aj[11] * xtemp2;
+			 	aj        += 12;
+			}
+
+			for ( ; j<n; j++ )
+			{
+				y_ptr[j]  += aj[0] * xtemp0 + aj[1] * xtemp1 + aj[2] * xtemp2;
+			 	aj        += 3;
+			}
+
+		}
+		else
+		{
+			for ( j=0; j<n; j++ )
+			{
+				*y_ptr += *aj * xtemp0 + *(aj+1) * xtemp1 + *(aj+2) * xtemp2;
+			 	y_ptr += inc_y;
+			 	aj    += lda;
+			}
 		}
 		return(0);
-
 	}
 
 	if ( m3 == 2 )
@@ -441,11 +464,38 @@ int CNAME(BLASLONG m, BLASLONG n, BLASLONG dummy1, FLOAT alpha, FLOAT *a, BLASLO
 
 		FLOAT *aj = a_ptr;
 		y_ptr = y;
-		for ( j=0; j<n; j++ )
+
+		if ( lda == 2 && inc_y == 1 )
 		{
-			*y_ptr += *aj * xtemp0 + *(aj+1) * xtemp1 ;
-			 y_ptr += inc_y;
-			 aj    += lda;
+
+			for ( j=0; j< ( n & -4) ; j+=4 )
+			{
+				y_ptr[j]   += aj[0] * xtemp0 + aj[1] * xtemp1 ;
+				y_ptr[j+1] += aj[2] * xtemp0 + aj[3] * xtemp1 ;
+				y_ptr[j+2] += aj[4] * xtemp0 + aj[5] * xtemp1 ;
+				y_ptr[j+3] += aj[6] * xtemp0 + aj[7] * xtemp1 ;
+			 	aj         += 8;
+
+			}
+
+			for ( ; j<n; j++ )
+			{
+				y_ptr[j] += aj[0] * xtemp0 + aj[1] * xtemp1 ;
+			 	aj       += 2;
+			}
+
+		}
+		else
+		{
+
+			for ( j=0; j<n; j++ )
+			{
+				*y_ptr += *aj * xtemp0 + *(aj+1) * xtemp1 ;
+			 	y_ptr += inc_y;
+			 	aj    += lda;
+			}
+
+
 		}
 		return(0);
 
@@ -454,13 +504,33 @@ int CNAME(BLASLONG m, BLASLONG n, BLASLONG dummy1, FLOAT alpha, FLOAT *a, BLASLO
 	FLOAT xtemp = *x_ptr * alpha;
 	FLOAT *aj = a_ptr;
 	y_ptr = y;
-	for ( j=0; j<n; j++ )
+	if ( lda == 1 && inc_y == 1 )
 	{
-		*y_ptr += *aj * xtemp;
-		 y_ptr += inc_y;
-		 aj    += lda;
+		for ( j=0; j< ( n & -4) ; j+=4 )
+		{
+			y_ptr[j]   += aj[j]   * xtemp;
+			y_ptr[j+1] += aj[j+1] * xtemp;
+			y_ptr[j+2] += aj[j+2] * xtemp;
+			y_ptr[j+3] += aj[j+3] * xtemp;
+		}
+		for ( ; j<n   ; j++ )
+		{
+			y_ptr[j] += aj[j] * xtemp;
+		}
+
+
+
 	}
-	
+	else
+	{
+		for ( j=0; j<n; j++ )
+		{
+			*y_ptr += *aj * xtemp;
+		 	y_ptr += inc_y;
+		 	aj    += lda;
+		}
+	}
+
 	return(0);
 }