runtime: improve performance of memclr, memmove on ppc64x

This improves the asm implementations for memmove and memclr on
ppc64x through use of vsx loads and stores when size is >= 32 bytes.
For memclr, dcbz is used when the size is >= 512 and aligned to 128.

Memclr/64       13.3ns ± 0%     10.7ns ± 0%   -19.55%  (p=0.000 n=8+7)
Memclr/96       14.9ns ± 0%     11.4ns ± 0%   -23.49%  (p=0.000 n=8+8)
Memclr/128      16.3ns ± 0%     12.3ns ± 0%   -24.54%  (p=0.000 n=8+8)
Memclr/160      17.3ns ± 0%     13.0ns ± 0%   -24.86%  (p=0.000 n=8+8)
Memclr/256      20.0ns ± 0%     15.3ns ± 0%   -23.62%  (p=0.000 n=8+8)
Memclr/512      34.2ns ± 0%     10.2ns ± 0%   -70.20%  (p=0.000 n=8+8)
Memclr/4096      178ns ± 0%       23ns ± 0%   -87.13%  (p=0.000 n=8+8)
Memclr/65536    2.67µs ± 0%     0.30µs ± 0%   -88.89%  (p=0.000 n=7+8)
Memclr/1M       43.2µs ± 0%     10.0µs ± 0%   -76.85%  (p=0.000 n=8+8)
Memclr/4M        173µs ± 0%       40µs ± 0%   -76.88%  (p=0.000 n=8+8)
Memclr/8M        349µs ± 0%       82µs ± 0%   -76.58%  (p=0.000 n=8+8)
Memclr/16M       701µs ± 7%      672µs ± 0%    -4.05%  (p=0.040 n=8+7)
Memclr/64M      2.70ms ± 0%     2.67ms ± 0%    -0.96%  (p=0.000 n=8+7)

Memmove/32      6.59ns ± 0%    5.84ns ± 0%  -11.34%  (p=0.029 n=4+4)
Memmove/64      7.91ns ± 0%    6.97ns ± 0%  -11.92%  (p=0.029 n=4+4)
Memmove/128     10.5ns ± 0%     8.8ns ± 0%  -16.24%  (p=0.029 n=4+4)
Memmove/256     21.0ns ± 0%    12.9ns ± 0%  -38.57%  (p=0.029 n=4+4)
Memmove/512     28.4ns ± 0%    26.2ns ± 0%   -7.75%  (p=0.029 n=4+4)
Memmove/1024    48.2ns ± 1%    39.4ns ± 0%  -18.26%  (p=0.029 n=4+4)
Memmove/2048    85.4ns ± 0%    69.0ns ± 0%  -19.20%  (p=0.029 n=4+4)
Memmove/4096     159ns ± 0%     128ns ± 0%  -19.50%  (p=0.029 n=4+4)

Change-Id: I8c1adf88790845bf31444a15249456006eb5bf8b
Reviewed-on: https://go-review.googlesource.com/c/141217
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Munday <mike.munday@ibm.com>

src/runtime/memclr_ppc64x.s

@@ -14,34 +14,68 @@ TEXT runtime·memclrNoHeapPointers(SB), NOSPLIT|NOFRAME, $0-16
 	// Determine if there are doublewords to clear
 check:
 	ANDCC $7, R4, R5  // R5: leftover bytes to clear
-	SRAD  $3, R4, R6  // R6: double words to clear
+	SRD   $3, R4, R6  // R6: double words to clear
 	CMP   R6, $0, CR1 // CR1[EQ] set if no double words
 
-	BC     12, 6, nozerolarge // only single bytes
+	BC    12, 6, nozerolarge // only single bytes
-	MOVD   R6, CTR            // R6 = number of double words
+	CMP   R4, $512
-	SRADCC $2, R6, R7         // 32 byte chunks?
+	BLT   under512           // special case for < 512
-	BNE    zero32setup
+	ANDCC $127, R3, R8       // check for 128 alignment of address
+	BEQ   zero512setup
+
+	ANDCC $7, R3, R15
+	BEQ   zero512xsetup // at least 8 byte aligned
+
+	// zero bytes up to 8 byte alignment
+
+	ANDCC $1, R3, R15 // check for byte alignment
+	BEQ   byte2
+	MOVB  R0, 0(R3)   // zero 1 byte
+	ADD   $1, R3      // bump ptr by 1
+	ADD   $-1, R4
+
+byte2:
+	ANDCC $2, R3, R15 // check for 2 byte alignment
+	BEQ   byte4
+	MOVH  R0, 0(R3)   // zero 2 bytes
+	ADD   $2, R3      // bump ptr by 2
+	ADD   $-2, R4
+
+byte4:
+	ANDCC $4, R3, R15   // check for 4 byte alignment
+	BEQ   zero512xsetup
+	MOVW  R0, 0(R3)     // zero 4 bytes
+	ADD   $4, R3        // bump ptr by 4
+	ADD   $-4, R4
+	BR    zero512xsetup // ptr should now be 8 byte aligned
+
+under512:
+	MOVD  R6, CTR     // R6 = number of double words
+	SRDCC $2, R6, R7  // 32 byte chunks?
+	BNE   zero32setup
 
 	// Clear double words
 
 zero8:
 	MOVD R0, 0(R3)    // double word
 	ADD  $8, R3
+	ADD  $-8, R4
 	BC   16, 0, zero8 // dec ctr, br zero8 if ctr not 0
-	BR   nozerolarge  // handle remainder
+	BR   nozerolarge  // handle leftovers
 
 	// Prepare to clear 32 bytes at a time.
 
 zero32setup:
-	DCBTST (R3)    // prepare data cache
+	DCBTST (R3)             // prepare data cache
-	MOVD   R7, CTR // number of 32 byte chunks
+	XXLXOR VS32, VS32, VS32 // clear VS32 (V0)
+	MOVD   R7, CTR          // number of 32 byte chunks
+	MOVD   $16, R8
 
 zero32:
-	MOVD    R0, 0(R3)       // clear 4 double words
+	STXVD2X VS32, (R3+R0)   // store 16 bytes
-	MOVD    R0, 8(R3)
+	STXVD2X VS32, (R3+R8)
-	MOVD    R0, 16(R3)
-	MOVD    R0, 24(R3)
 	ADD     $32, R3
+	ADD     $-32, R4
 	BC      16, 0, zero32   // dec ctr, br zero32 if ctr not 0
 	RLDCLCC $61, R4, $3, R6 // remaining doublewords
 	BEQ     nozerolarge
@@ -49,8 +83,8 @@ zero32:
 	BR      zero8
 
 nozerolarge:
-	CMP R5, $0   // any remaining bytes
+	ANDCC $7, R4, R5 // any remaining bytes
-	BC  4, 1, LR // ble lr
+	BC    4, 1, LR   // ble lr
 
 zerotail:
 	MOVD R5, CTR // set up to clear tail bytes
@@ -60,3 +94,70 @@ zerotailloop:
 	ADD  $1, R3
 	BC   16, 0, zerotailloop // dec ctr, br zerotailloop if ctr not 0
 	RET
+
+zero512xsetup:  // 512 chunk with extra needed
+	ANDCC $8, R3, R11    // 8 byte alignment?
+	BEQ   zero512setup16
+	MOVD  R0, 0(R3)      // clear 8 bytes
+	ADD   $8, R3         // update ptr to next 8
+	ADD   $-8, R4        // dec count by 8
+
+zero512setup16:
+	ANDCC $127, R3, R14 // < 128 byte alignment
+	BEQ   zero512setup  // handle 128 byte alignment
+	MOVD  $128, R15
+	SUB   R14, R15, R14 // find increment to 128 alignment
+	SRD   $4, R14, R15  // number of 16 byte chunks
+
+zero512presetup:
+	MOVD   R15, CTR         // loop counter of 16 bytes
+	XXLXOR VS32, VS32, VS32 // clear VS32 (V0)
+
+zero512preloop:  // clear up to 128 alignment
+	STXVD2X VS32, (R3+R0)         // clear 16 bytes
+	ADD     $16, R3               // update ptr
+	ADD     $-16, R4              // dec count
+	BC      16, 0, zero512preloop
+
+zero512setup:  // setup for dcbz loop
+	CMP  R4, $512   // check if at least 512
+	BLT  remain
+	SRD  $9, R4, R8 // loop count for 512 chunks
+	MOVD R8, CTR    // set up counter
+	MOVD $128, R9   // index regs for 128 bytes
+	MOVD $256, R10
+	MOVD $384, R11
+
+zero512:
+	DCBZ (R3+R0)        // clear first chunk
+	DCBZ (R3+R9)        // clear second chunk
+	DCBZ (R3+R10)       // clear third chunk
+	DCBZ (R3+R11)       // clear fourth chunk
+	ADD  $512, R3
+	ADD  $-512, R4
+	BC   16, 0, zero512
+
+remain:
+	CMP  R4, $128  // check if 128 byte chunks left
+	BLT  smaller
+	DCBZ (R3+R0)   // clear 128
+	ADD  $128, R3
+	ADD  $-128, R4
+	BR   remain
+
+smaller:
+	ANDCC $127, R4, R7 // find leftovers
+	BEQ   done
+	CMP   R7, $64      // more than 64, do 32 at a time
+	BLT   zero8setup   // less than 64, do 8 at a time
+	SRD   $5, R7, R7   // set up counter for 32
+	BR    zero32setup
+
+zero8setup:
+	SRDCC $3, R7, R7  // less than 8 bytes
+	BEQ   nozerolarge
+	MOVD  R7, CTR
+	BR    zero8
+
+done:
+	RET

src/runtime/memmove_ppc64x.s

@@ -16,7 +16,7 @@ TEXT runtime·memmove(SB), NOSPLIT|NOFRAME, $0-24
 	// copy so a more efficient move can be done
 check:
 	ANDCC	$7, R5, R7	// R7: bytes to copy
-	SRAD	$3, R5, R6	// R6: double words to copy
+	SRD	$3, R5, R6	// R6: double words to copy
 	CMP	R6, $0, CR1	// CR1[EQ] set if no double words to copy
 
 	// Determine overlap by subtracting dest - src and comparing against the
@@ -31,9 +31,9 @@ check:
 	// Copying forward if no overlap.
 
 	BC	12, 6, noforwardlarge	// "BEQ CR1, noforwardlarge"
-	MOVD	R6,CTR			// R6 = number of double words
+	SRDCC	$2,R6,R8		// 32 byte chunks?
-	SRADCC	$2,R6,R8		// 32 byte chunks?
 	BNE	forward32setup		//
+	MOVD	R6,CTR			// R6 = number of double words
 
 	// Move double words
 
@@ -51,17 +51,14 @@ forward32setup:
 	DCBTST	(R3)			// prepare data cache
 	DCBT	(R4)
 	MOVD	R8, CTR			// double work count
+	MOVD	$16, R8
 
 forward32:
-	MOVD	0(R4), R8		// load 4 double words
+	LXVD2X	(R4+R0), VS32		// load 16 bytes
-	MOVD	8(R4), R9
+	LXVD2X	(R4+R8), VS33
-	MOVD	16(R4), R14
+	ADD	$32, R4
-	MOVD	24(R4), R15
+	STXVD2X	VS32, (R3+R0)		// store 16 bytes
-	ADD	$32,R4
+	STXVD2X	VS33, (R3+R8)
-	MOVD	R8, 0(R3)		// store those 4
-	MOVD	R9, 8(R3)
-	MOVD	R14,16(R3)
-	MOVD	R15,24(R3)
 	ADD	$32,R3			// bump up for next set
 	BC	16, 0, forward32	// continue
 	RLDCLCC	$61,R5,$3,R6		// remaining doublewords
@@ -71,7 +68,7 @@ forward32:
 
 noforwardlarge:
 	CMP	R7,$0			// any remaining bytes
-	BC	4, 1, LR
+	BC	4, 1, LR		// ble lr
 
 forwardtail:
 	MOVD	R7, CTR			// move tail bytes
@@ -101,19 +98,39 @@ backwardtailloop:
 	SUB	$1,R4
 	MOVBZ 	R8, -1(R3)
 	SUB	$1,R3
-	BC	16, 0, backwardtailloop
+	BC	16, 0, backwardtailloop // bndz
 
 nobackwardtail:
-	CMP	R6,$0
+	BC	4, 5, LR		// ble CR1 lr
-	BC	4, 5, LR
 
 backwardlarge:
 	MOVD	R6, CTR
+	SUB	R3, R4, R9		// Use vsx if moving
+	CMP	R9, $32			// at least 32 byte chunks
+	BLT	backwardlargeloop	// and distance >= 32
+	SRDCC	$2,R6,R8		// 32 byte chunks
+	BNE	backward32setup
 
 backwardlargeloop:
 	MOVD 	-8(R4), R8
 	SUB	$8,R4
 	MOVD 	R8, -8(R3)
 	SUB	$8,R3
-	BC	16, 0, backwardlargeloop	//
+	BC	16, 0, backwardlargeloop // bndz
 	RET
+
+backward32setup:
+	MOVD	R8, CTR			// set up loop ctr
+	MOVD	$16, R8			// 32 bytes at at time
+
+backward32loop:
+	SUB	$32, R4
+	SUB	$32, R3
+	LXVD2X	(R4+R0), VS32           // load 16 bytes
+	LXVD2X	(R4+R8), VS33
+	STXVD2X	VS32, (R3+R0)           // store 16 bytes
+	STXVD2X	VS33, (R3+R8)
+	BC      16, 0, backward32loop   // bndz
+	BC	4, 5, LR		// ble CR1 lr
+	MOVD	R6, CTR
+	BR	backwardlargeloop