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From:   Danny Tsen <dtsen@linux.ibm.com>
To:     linux-crypto@vger.kernel.org
Cc:     herbert@gondor.apana.org.au, leitao@debian.org,
        nayna@linux.ibm.com, appro@cryptogams.org,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        mpe@ellerman.id.au, ltcgcw@linux.vnet.ibm.com, dtsen@us.ibm.com,
        Danny Tsen <dtsen@linux.ibm.com>
Subject: [PATCH] crypto: vmx: Improved AES/XTS performance of 6-way unrolling for ppc.
Date:   Tue, 29 Aug 2023 11:37:04 -0400
Message-Id: <20230829153704.135475-1-dtsen@linux.ibm.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Improve AES/XTS performance of 6-way unrolling for PowerPC up
to 17% with tcrypt.  This is done by using one instruction,
vpermxor, to replace xor and vsldoi.

This patch has been tested with the kernel crypto module tcrypt.ko and
has passed the selftest.  The patch is also tested with
CONFIG_CRYPTO_MANAGER_EXTRA_TESTS enabled.

Signed-off-by: Danny Tsen <dtsen@linux.ibm.com>
---
 drivers/crypto/vmx/aesp8-ppc.pl | 141 +++++++++++++++++++++-----------
 1 file changed, 92 insertions(+), 49 deletions(-)

diff --git a/drivers/crypto/vmx/aesp8-ppc.pl b/drivers/crypto/vmx/aesp8-ppc.pl
index 50a0a18f35da..f729589d792e 100644
--- a/drivers/crypto/vmx/aesp8-ppc.pl
+++ b/drivers/crypto/vmx/aesp8-ppc.pl
@@ -132,11 +132,12 @@ rcon:
 .long	0x1b000000, 0x1b000000, 0x1b000000, 0x1b000000	?rev
 .long	0x0d0e0f0c, 0x0d0e0f0c, 0x0d0e0f0c, 0x0d0e0f0c	?rev
 .long	0,0,0,0						?asis
+.long	0x0f102132, 0x43546576, 0x8798a9ba, 0xcbdcedfe
 Lconsts:
 	mflr	r0
 	bcl	20,31,\$+4
 	mflr	$ptr	 #vvvvv "distance between . and rcon
-	addi	$ptr,$ptr,-0x48
+	addi	$ptr,$ptr,-0x58
 	mtlr	r0
 	blr
 	.long	0
@@ -2495,6 +2496,17 @@ _aesp8_xts_encrypt6x:
 	li		$x70,0x70
 	mtspr		256,r0
 
+	xxlor		2, 32+$eighty7, 32+$eighty7
+	vsldoi		$eighty7,$tmp,$eighty7,1        # 0x010101..87
+	xxlor		1, 32+$eighty7, 32+$eighty7
+
+	# Load XOR Lconsts.
+	mr		$x70, r6
+	bl		Lconsts
+	lxvw4x		0, $x40, r6		# load XOR contents
+	mr		r6, $x70
+	li		$x70,0x70
+
 	subi		$rounds,$rounds,3	# -4 in total
 
 	lvx		$rndkey0,$x00,$key1	# load key schedule
@@ -2537,69 +2549,77 @@ Load_xts_enc_key:
 	?vperm		v31,v31,$twk5,$keyperm
 	lvx		v25,$x10,$key_		# pre-load round[2]
 
+	# Switch to use the following codes with 0x010101..87 to generate tweak.
+	#     eighty7 = 0x010101..87
+	# vsrab         tmp, tweak, seven       # next tweak value, right shift 7 bits
+	# vand          tmp, tmp, eighty7       # last byte with carry
+	# vaddubm       tweak, tweak, tweak     # left shift 1 bit (x2)
+	# xxlor         vsx, 0, 0
+	# vpermxor      tweak, tweak, tmp, vsx
+
 	 vperm		$in0,$inout,$inptail,$inpperm
 	 subi		$inp,$inp,31		# undo "caller"
 	vxor		$twk0,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out0,$in0,$twk0
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in1, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in1
 
 	 lvx_u		$in1,$x10,$inp
 	vxor		$twk1,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in1,$in1,$in1,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out1,$in1,$twk1
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in2, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in2
 
 	 lvx_u		$in2,$x20,$inp
 	 andi.		$taillen,$len,15
 	vxor		$twk2,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in2,$in2,$in2,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out2,$in2,$twk2
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in3, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in3
 
 	 lvx_u		$in3,$x30,$inp
 	 sub		$len,$len,$taillen
 	vxor		$twk3,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in3,$in3,$in3,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out3,$in3,$twk3
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in4, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in4
 
 	 lvx_u		$in4,$x40,$inp
 	 subi		$len,$len,0x60
 	vxor		$twk4,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in4,$in4,$in4,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out4,$in4,$twk4
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in5, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in5
 
 	 lvx_u		$in5,$x50,$inp
 	 addi		$inp,$inp,0x60
 	vxor		$twk5,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in5,$in5,$in5,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out5,$in5,$twk5
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in0, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in0
 
 	vxor		v31,v31,$rndkey0
 	mtctr		$rounds
@@ -2625,6 +2645,8 @@ Loop_xts_enc6x:
 	lvx		v25,$x10,$key_		# round[4]
 	bdnz		Loop_xts_enc6x
 
+	xxlor		32+$eighty7, 1, 1	# 0x010101..87
+
 	subic		$len,$len,96		# $len-=96
 	 vxor		$in0,$twk0,v31		# xor with last round key
 	vcipher		$out0,$out0,v24
@@ -2634,7 +2656,6 @@ Loop_xts_enc6x:
 	 vaddubm	$tweak,$tweak,$tweak
 	vcipher		$out2,$out2,v24
 	vcipher		$out3,$out3,v24
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vcipher		$out4,$out4,v24
 	vcipher		$out5,$out5,v24
 
@@ -2642,7 +2663,8 @@ Loop_xts_enc6x:
 	 vand		$tmp,$tmp,$eighty7
 	vcipher		$out0,$out0,v25
 	vcipher		$out1,$out1,v25
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in1, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in1
 	vcipher		$out2,$out2,v25
 	vcipher		$out3,$out3,v25
 	 vxor		$in1,$twk1,v31
@@ -2653,13 +2675,13 @@ Loop_xts_enc6x:
 
 	and		r0,r0,$len
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vcipher		$out0,$out0,v26
 	vcipher		$out1,$out1,v26
 	 vand		$tmp,$tmp,$eighty7
 	vcipher		$out2,$out2,v26
 	vcipher		$out3,$out3,v26
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in2, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in2
 	vcipher		$out4,$out4,v26
 	vcipher		$out5,$out5,v26
 
@@ -2673,7 +2695,6 @@ Loop_xts_enc6x:
 	 vaddubm	$tweak,$tweak,$tweak
 	vcipher		$out0,$out0,v27
 	vcipher		$out1,$out1,v27
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vcipher		$out2,$out2,v27
 	vcipher		$out3,$out3,v27
 	 vand		$tmp,$tmp,$eighty7
@@ -2681,7 +2702,8 @@ Loop_xts_enc6x:
 	vcipher		$out5,$out5,v27
 
 	addi		$key_,$sp,$FRAME+15	# rewind $key_
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in3, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in3
 	vcipher		$out0,$out0,v28
 	vcipher		$out1,$out1,v28
 	 vxor		$in3,$twk3,v31
@@ -2690,7 +2712,6 @@ Loop_xts_enc6x:
 	vcipher		$out2,$out2,v28
 	vcipher		$out3,$out3,v28
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vcipher		$out4,$out4,v28
 	vcipher		$out5,$out5,v28
 	lvx		v24,$x00,$key_		# re-pre-load round[1]
@@ -2698,7 +2719,8 @@ Loop_xts_enc6x:
 
 	vcipher		$out0,$out0,v29
 	vcipher		$out1,$out1,v29
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in4, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in4
 	vcipher		$out2,$out2,v29
 	vcipher		$out3,$out3,v29
 	 vxor		$in4,$twk4,v31
@@ -2708,14 +2730,14 @@ Loop_xts_enc6x:
 	vcipher		$out5,$out5,v29
 	lvx		v25,$x10,$key_		# re-pre-load round[2]
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 
 	vcipher		$out0,$out0,v30
 	vcipher		$out1,$out1,v30
 	 vand		$tmp,$tmp,$eighty7
 	vcipher		$out2,$out2,v30
 	vcipher		$out3,$out3,v30
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in5, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in5
 	vcipher		$out4,$out4,v30
 	vcipher		$out5,$out5,v30
 	 vxor		$in5,$twk5,v31
@@ -2725,7 +2747,6 @@ Loop_xts_enc6x:
 	vcipherlast	$out0,$out0,$in0
 	 lvx_u		$in0,$x00,$inp		# load next input block
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vcipherlast	$out1,$out1,$in1
 	 lvx_u		$in1,$x10,$inp
 	vcipherlast	$out2,$out2,$in2
@@ -2738,7 +2759,10 @@ Loop_xts_enc6x:
 	vcipherlast	$out4,$out4,$in4
 	 le?vperm	$in2,$in2,$in2,$leperm
 	 lvx_u		$in4,$x40,$inp
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		10, 32+$in0, 32+$in0
+	 xxlor		32+$in0, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in0
+	 xxlor		32+$in0, 10, 10
 	vcipherlast	$tmp,$out5,$in5		# last block might be needed
 						# in stealing mode
 	 le?vperm	$in3,$in3,$in3,$leperm
@@ -2771,6 +2795,8 @@ Loop_xts_enc6x:
 	mtctr		$rounds
 	beq		Loop_xts_enc6x		# did $len-=96 borrow?
 
+	xxlor		32+$eighty7, 2, 2	# 0x010101..87
+
 	addic.		$len,$len,0x60
 	beq		Lxts_enc6x_zero
 	cmpwi		$len,0x20
@@ -3147,6 +3173,17 @@ _aesp8_xts_decrypt6x:
 	li		$x70,0x70
 	mtspr		256,r0
 
+	xxlor		2, 32+$eighty7, 32+$eighty7
+	vsldoi		$eighty7,$tmp,$eighty7,1        # 0x010101..87
+	xxlor		1, 32+$eighty7, 32+$eighty7
+
+	# Load XOR Lconsts.
+	mr		$x70, r6
+	bl		Lconsts
+	lxvw4x		0, $x40, r6		# load XOR contents
+	mr		r6, $x70
+	li		$x70,0x70
+
 	subi		$rounds,$rounds,3	# -4 in total
 
 	lvx		$rndkey0,$x00,$key1	# load key schedule
@@ -3194,64 +3231,64 @@ Load_xts_dec_key:
 	vxor		$twk0,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out0,$in0,$twk0
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in1, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in1
 
 	 lvx_u		$in1,$x10,$inp
 	vxor		$twk1,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in1,$in1,$in1,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out1,$in1,$twk1
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in2, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in2
 
 	 lvx_u		$in2,$x20,$inp
 	 andi.		$taillen,$len,15
 	vxor		$twk2,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in2,$in2,$in2,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out2,$in2,$twk2
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in3, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in3
 
 	 lvx_u		$in3,$x30,$inp
 	 sub		$len,$len,$taillen
 	vxor		$twk3,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in3,$in3,$in3,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out3,$in3,$twk3
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in4, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in4
 
 	 lvx_u		$in4,$x40,$inp
 	 subi		$len,$len,0x60
 	vxor		$twk4,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in4,$in4,$in4,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out4,$in4,$twk4
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in5, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in5
 
 	 lvx_u		$in5,$x50,$inp
 	 addi		$inp,$inp,0x60
 	vxor		$twk5,$tweak,$rndkey0
 	vsrab		$tmp,$tweak,$seven	# next tweak value
 	vaddubm		$tweak,$tweak,$tweak
-	vsldoi		$tmp,$tmp,$tmp,15
 	 le?vperm	$in5,$in5,$in5,$leperm
 	vand		$tmp,$tmp,$eighty7
 	 vxor		$out5,$in5,$twk5
-	vxor		$tweak,$tweak,$tmp
+	xxlor		32+$in0, 0, 0
+	vpermxor	$tweak, $tweak, $tmp, $in0
 
 	vxor		v31,v31,$rndkey0
 	mtctr		$rounds
@@ -3277,6 +3314,8 @@ Loop_xts_dec6x:
 	lvx		v25,$x10,$key_		# round[4]
 	bdnz		Loop_xts_dec6x
 
+	xxlor		32+$eighty7, 1, 1	# 0x010101..87
+
 	subic		$len,$len,96		# $len-=96
 	 vxor		$in0,$twk0,v31		# xor with last round key
 	vncipher	$out0,$out0,v24
@@ -3286,7 +3325,6 @@ Loop_xts_dec6x:
 	 vaddubm	$tweak,$tweak,$tweak
 	vncipher	$out2,$out2,v24
 	vncipher	$out3,$out3,v24
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vncipher	$out4,$out4,v24
 	vncipher	$out5,$out5,v24
 
@@ -3294,7 +3332,8 @@ Loop_xts_dec6x:
 	 vand		$tmp,$tmp,$eighty7
 	vncipher	$out0,$out0,v25
 	vncipher	$out1,$out1,v25
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in1, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in1
 	vncipher	$out2,$out2,v25
 	vncipher	$out3,$out3,v25
 	 vxor		$in1,$twk1,v31
@@ -3305,13 +3344,13 @@ Loop_xts_dec6x:
 
 	and		r0,r0,$len
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vncipher	$out0,$out0,v26
 	vncipher	$out1,$out1,v26
 	 vand		$tmp,$tmp,$eighty7
 	vncipher	$out2,$out2,v26
 	vncipher	$out3,$out3,v26
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in2, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in2
 	vncipher	$out4,$out4,v26
 	vncipher	$out5,$out5,v26
 
@@ -3325,7 +3364,6 @@ Loop_xts_dec6x:
 	 vaddubm	$tweak,$tweak,$tweak
 	vncipher	$out0,$out0,v27
 	vncipher	$out1,$out1,v27
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vncipher	$out2,$out2,v27
 	vncipher	$out3,$out3,v27
 	 vand		$tmp,$tmp,$eighty7
@@ -3333,7 +3371,8 @@ Loop_xts_dec6x:
 	vncipher	$out5,$out5,v27
 
 	addi		$key_,$sp,$FRAME+15	# rewind $key_
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in3, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in3
 	vncipher	$out0,$out0,v28
 	vncipher	$out1,$out1,v28
 	 vxor		$in3,$twk3,v31
@@ -3342,7 +3381,6 @@ Loop_xts_dec6x:
 	vncipher	$out2,$out2,v28
 	vncipher	$out3,$out3,v28
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vncipher	$out4,$out4,v28
 	vncipher	$out5,$out5,v28
 	lvx		v24,$x00,$key_		# re-pre-load round[1]
@@ -3350,7 +3388,8 @@ Loop_xts_dec6x:
 
 	vncipher	$out0,$out0,v29
 	vncipher	$out1,$out1,v29
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in4, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in4
 	vncipher	$out2,$out2,v29
 	vncipher	$out3,$out3,v29
 	 vxor		$in4,$twk4,v31
@@ -3360,14 +3399,14 @@ Loop_xts_dec6x:
 	vncipher	$out5,$out5,v29
 	lvx		v25,$x10,$key_		# re-pre-load round[2]
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 
 	vncipher	$out0,$out0,v30
 	vncipher	$out1,$out1,v30
 	 vand		$tmp,$tmp,$eighty7
 	vncipher	$out2,$out2,v30
 	vncipher	$out3,$out3,v30
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		32+$in5, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in5
 	vncipher	$out4,$out4,v30
 	vncipher	$out5,$out5,v30
 	 vxor		$in5,$twk5,v31
@@ -3377,7 +3416,6 @@ Loop_xts_dec6x:
 	vncipherlast	$out0,$out0,$in0
 	 lvx_u		$in0,$x00,$inp		# load next input block
 	 vaddubm	$tweak,$tweak,$tweak
-	 vsldoi		$tmp,$tmp,$tmp,15
 	vncipherlast	$out1,$out1,$in1
 	 lvx_u		$in1,$x10,$inp
 	vncipherlast	$out2,$out2,$in2
@@ -3390,7 +3428,10 @@ Loop_xts_dec6x:
 	vncipherlast	$out4,$out4,$in4
 	 le?vperm	$in2,$in2,$in2,$leperm
 	 lvx_u		$in4,$x40,$inp
-	 vxor		$tweak,$tweak,$tmp
+	 xxlor		10, 32+$in0, 32+$in0
+	 xxlor		32+$in0, 0, 0
+	 vpermxor	$tweak, $tweak, $tmp, $in0
+	 xxlor		32+$in0, 10, 10
 	vncipherlast	$out5,$out5,$in5
 	 le?vperm	$in3,$in3,$in3,$leperm
 	 lvx_u		$in5,$x50,$inp
@@ -3421,6 +3462,8 @@ Loop_xts_dec6x:
 	mtctr		$rounds
 	beq		Loop_xts_dec6x		# did $len-=96 borrow?
 
+	xxlor		32+$eighty7, 2, 2	# 0x010101..87
+
 	addic.		$len,$len,0x60
 	beq		Lxts_dec6x_zero
 	cmpwi		$len,0x20
-- 
2.31.1