From eb36af59e5316a9849928d72629875eb84e8fc9a Mon Sep 17 00:00:00 2001
From: Sun Yimin <emmansun@users.noreply.github.com>
Date: Wed, 28 Aug 2024 10:13:59 +0800
Subject: [PATCH] internal/subtle: s390x, handle tail

---
 internal/subtle/xor_s390x.s | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/internal/subtle/xor_s390x.s b/internal/subtle/xor_s390x.s
index b284f04..4d97b23 100644
--- a/internal/subtle/xor_s390x.s
+++ b/internal/subtle/xor_s390x.s
@@ -13,7 +13,7 @@ TEXT ·xorBytes(SB),NOSPLIT,$0-32
 	MOVD	n+24(FP), R4
 
 	MOVD	$0, R5
-	CMPBLT	R4, $16, less_than16
+	CMPBLT	R4, $16, tail
 
 loop16b:
 	VL 0(R2)(R5*1), V0
@@ -24,8 +24,8 @@ loop16b:
 	SUB	$16, R4
 	CMPBGE	R4, $16, loop16b
 
-less_than16:
-	CMPBLT	R4, $8, tail
+tail:
+	CMPBLT	R4, $8, less_than8
 	MOVD	0(R2)(R5*1), R7
 	MOVD	0(R3)(R5*1), R8
 	XOR	R7, R8
@@ -33,15 +33,30 @@ less_than16:
 	LAY	8(R5), R5
 	SUB	$8, R4
 
-tail:
+less_than8:
+	CMPBLT	R4, $4, less_than4
+	MOVWZ	0(R2)(R5*1), R7
+	MOVWZ	0(R3)(R5*1), R8
+	XOR	R7, R8
+	MOVW	R8, 0(R1)(R5*1)
+	LAY	4(R5), R5
+	SUB	$4, R4
+
+less_than4:
+	CMPBLT	R4, $2, less_than2
+	MOVHZ	0(R2)(R5*1), R7
+	MOVHZ	0(R3)(R5*1), R8
+	XOR	R7, R8
+	MOVH	R8, 0(R1)(R5*1)
+	LAY	2(R5), R5
+	SUB	$2, R4
+
+less_than2:
 	CMPBEQ	R4, $0, done
 	MOVB	0(R2)(R5*1), R7
 	MOVB	0(R3)(R5*1), R8
 	XOR	R7, R8
 	MOVB	R8, 0(R1)(R5*1)
-	LAY	1(R5), R5
-	SUB	$1, R4
-	BR	tail
 
 done:
 	RET