linux_kernel/arch/powerpc/lib/memcmp_64.S

/*
 * Author: Anton Blanchard <anton@au.ibm.com>
 * Copyright 2015 IBM Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#include <asm/ppc_asm.h>
#include <asm/export.h>
#include <asm/ppc-opcode.h>

#define off8	r6
#define off16	r7
#define off24	r8

#define rA	r9
#define rB	r10
#define rC	r11
#define rD	r27
#define rE	r28
#define rF	r29
#define rG	r30
#define rH	r31

#ifdef __LITTLE_ENDIAN__
#define LH	lhbrx
#define LW	lwbrx
#define LD	ldbrx
#define LVS	lvsr
#define VPERM(_VRT,_VRA,_VRB,_VRC) \
	vperm _VRT,_VRB,_VRA,_VRC
#else
#define LH	lhzx
#define LW	lwzx
#define LD	ldx
#define LVS	lvsl
#define VPERM(_VRT,_VRA,_VRB,_VRC) \
	vperm _VRT,_VRA,_VRB,_VRC
#endif

#define VMX_THRESH 4096
#define ENTER_VMX_OPS	\
	mflr    r0;	\
	std     r3,-STACKFRAMESIZE+STK_REG(R31)(r1); \
	std     r4,-STACKFRAMESIZE+STK_REG(R30)(r1); \
	std     r5,-STACKFRAMESIZE+STK_REG(R29)(r1); \
	std     r0,16(r1); \
	stdu    r1,-STACKFRAMESIZE(r1); \
	bl      enter_vmx_ops; \
	cmpwi   cr1,r3,0; \
	ld      r0,STACKFRAMESIZE+16(r1); \
	ld      r3,STK_REG(R31)(r1); \
	ld      r4,STK_REG(R30)(r1); \
	ld      r5,STK_REG(R29)(r1); \
	addi	r1,r1,STACKFRAMESIZE; \
	mtlr    r0

#define EXIT_VMX_OPS \
	mflr    r0; \
	std     r3,-STACKFRAMESIZE+STK_REG(R31)(r1); \
	std     r4,-STACKFRAMESIZE+STK_REG(R30)(r1); \
	std     r5,-STACKFRAMESIZE+STK_REG(R29)(r1); \
	std     r0,16(r1); \
	stdu    r1,-STACKFRAMESIZE(r1); \
	bl      exit_vmx_ops; \
	ld      r0,STACKFRAMESIZE+16(r1); \
	ld      r3,STK_REG(R31)(r1); \
	ld      r4,STK_REG(R30)(r1); \
	ld      r5,STK_REG(R29)(r1); \
	addi	r1,r1,STACKFRAMESIZE; \
	mtlr    r0

/*
 * LD_VSR_CROSS16B load the 2nd 16 bytes for _vaddr which is unaligned with
 * 16 bytes boundary and permute the result with the 1st 16 bytes.

 *    |  y y y y y y y y y y y y y 0 1 2 | 3 4 5 6 7 8 9 a b c d e f z z z |
 *    ^                                  ^                                 ^
 * 0xbbbb10                          0xbbbb20                          0xbbb30
 *                                 ^
 *                                _vaddr
 *
 *
 * _vmask is the mask generated by LVS
 * _v1st_qw is the 1st aligned QW of current addr which is already loaded.
 *   for example: 0xyyyyyyyyyyyyy012 for big endian
 * _v2nd_qw is the 2nd aligned QW of cur _vaddr to be loaded.
 *   for example: 0x3456789abcdefzzz for big endian
 * The permute result is saved in _v_res.
 *   for example: 0x0123456789abcdef for big endian.
 */
#define LD_VSR_CROSS16B(_vaddr,_vmask,_v1st_qw,_v2nd_qw,_v_res) \
        lvx     _v2nd_qw,_vaddr,off16; \
        VPERM(_v_res,_v1st_qw,_v2nd_qw,_vmask)

/*
 * There are 2 categories for memcmp:
 * 1) src/dst has the same offset to the 8 bytes boundary. The handlers
 * are named like .Lsameoffset_xxxx
 * 2) src/dst has different offset to the 8 bytes boundary. The handlers
 * are named like .Ldiffoffset_xxxx
 */
_GLOBAL_TOC(memcmp)
	cmpdi	cr1,r5,0

	/* Use the short loop if the src/dst addresses are not
	 * with the same offset of 8 bytes align boundary.
	 */
	xor	r6,r3,r4
	andi.	r6,r6,7

	/* Fall back to short loop if compare at aligned addrs
	 * with less than 8 bytes.
	 */
	cmpdi   cr6,r5,7

	beq	cr1,.Lzero
	bgt	cr6,.Lno_short

.Lshort:
	mtctr	r5
1:	lbz	rA,0(r3)
	lbz	rB,0(r4)
	subf.	rC,rB,rA
	bne	.Lnon_zero
	bdz	.Lzero

	lbz	rA,1(r3)
	lbz	rB,1(r4)
	subf.	rC,rB,rA
	bne	.Lnon_zero
	bdz	.Lzero

	lbz	rA,2(r3)
	lbz	rB,2(r4)
	subf.	rC,rB,rA
	bne	.Lnon_zero
	bdz	.Lzero

	lbz	rA,3(r3)
	lbz	rB,3(r4)
	subf.	rC,rB,rA
	bne	.Lnon_zero

	addi	r3,r3,4
	addi	r4,r4,4

	bdnz	1b

.Lzero:
	li	r3,0
	blr

.Lno_short:
	dcbt	0,r3
	dcbt	0,r4
	bne	.Ldiffoffset_8bytes_make_align_start


.Lsameoffset_8bytes_make_align_start:
	/* attempt to compare bytes not aligned with 8 bytes so that
	 * rest comparison can run based on 8 bytes alignment.
	 */
	andi.   r6,r3,7

	/* Try to compare the first double word which is not 8 bytes aligned:
	 * load the first double word at (src & ~7UL) and shift left appropriate
	 * bits before comparision.
	 */
	rlwinm  r6,r3,3,26,28
	beq     .Lsameoffset_8bytes_aligned
	clrrdi	r3,r3,3
	clrrdi	r4,r4,3
	LD	rA,0,r3
	LD	rB,0,r4
	sld	rA,rA,r6
	sld	rB,rB,r6
	cmpld	cr0,rA,rB
	srwi	r6,r6,3
	bne	cr0,.LcmpAB_lightweight
	subfic  r6,r6,8
	subf.	r5,r6,r5
	addi	r3,r3,8
	addi	r4,r4,8
	beq	.Lzero

.Lsameoffset_8bytes_aligned:
	/* now we are aligned with 8 bytes.
	 * Use .Llong loop if left cmp bytes are equal or greater than 32B.
	 */
	cmpdi   cr6,r5,31
	bgt	cr6,.Llong

.Lcmp_lt32bytes:
	/* compare 1 ~ 31 bytes, at least r3 addr is 8 bytes aligned now */
	cmpdi   cr5,r5,7
	srdi    r0,r5,3
	ble	cr5,.Lcmp_rest_lt8bytes

	/* handle 8 ~ 31 bytes */
	clrldi  r5,r5,61
	mtctr   r0
2:
	LD	rA,0,r3
	LD	rB,0,r4
	cmpld	cr0,rA,rB
	addi	r3,r3,8
	addi	r4,r4,8
	bne	cr0,.LcmpAB_lightweight
	bdnz	2b

	cmpwi   r5,0
	beq	.Lzero

.Lcmp_rest_lt8bytes:
	/* Here we have only less than 8 bytes to compare with. at least s1
	 * Address is aligned with 8 bytes.
	 * The next double words are load and shift right with appropriate
	 * bits.
	 */
	subfic  r6,r5,8
	slwi	r6,r6,3
	LD	rA,0,r3
	LD	rB,0,r4
	srd	rA,rA,r6
	srd	rB,rB,r6
	cmpld	cr0,rA,rB
	bne	cr0,.LcmpAB_lightweight
	b	.Lzero

.Lnon_zero:
	mr	r3,rC
	blr

.Llong:
#ifdef CONFIG_ALTIVEC
BEGIN_FTR_SECTION
	/* Try to use vmx loop if length is equal or greater than 4K */
	cmpldi  cr6,r5,VMX_THRESH
	bge	cr6,.Lsameoffset_vmx_cmp
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)

.Llong_novmx_cmp:
#endif
	/* At least s1 addr is aligned with 8 bytes */
	li	off8,8
	li	off16,16
	li	off24,24

	std	r31,-8(r1)
	std	r30,-16(r1)
	std	r29,-24(r1)
	std	r28,-32(r1)
	std	r27,-40(r1)

	srdi	r0,r5,5
	mtctr	r0
	andi.	r5,r5,31

	LD	rA,0,r3
	LD	rB,0,r4

	LD	rC,off8,r3
	LD	rD,off8,r4

	LD	rE,off16,r3
	LD	rF,off16,r4

	LD	rG,off24,r3
	LD	rH,off24,r4
	cmpld	cr0,rA,rB

	addi	r3,r3,32
	addi	r4,r4,32

	bdz	.Lfirst32

	LD	rA,0,r3
	LD	rB,0,r4
	cmpld	cr1,rC,rD

	LD	rC,off8,r3
	LD	rD,off8,r4
	cmpld	cr6,rE,rF

	LD	rE,off16,r3
	LD	rF,off16,r4
	cmpld	cr7,rG,rH
	bne	cr0,.LcmpAB

	LD	rG,off24,r3
	LD	rH,off24,r4
	cmpld	cr0,rA,rB
	bne	cr1,.LcmpCD

	addi	r3,r3,32
	addi	r4,r4,32

	bdz	.Lsecond32

	.balign	16

1:	LD	rA,0,r3
	LD	rB,0,r4
	cmpld	cr1,rC,rD
	bne	cr6,.LcmpEF

	LD	rC,off8,r3
	LD	rD,off8,r4
	cmpld	cr6,rE,rF
	bne	cr7,.LcmpGH

	LD	rE,off16,r3
	LD	rF,off16,r4
	cmpld	cr7,rG,rH
	bne	cr0,.LcmpAB

	LD	rG,off24,r3
	LD	rH,off24,r4
	cmpld	cr0,rA,rB
	bne	cr1,.LcmpCD

	addi	r3,r3,32
	addi	r4,r4,32

	bdnz	1b

.Lsecond32:
	cmpld	cr1,rC,rD
	bne	cr6,.LcmpEF

	cmpld	cr6,rE,rF
	bne	cr7,.LcmpGH

	cmpld	cr7,rG,rH
	bne	cr0,.LcmpAB

	bne	cr1,.LcmpCD
	bne	cr6,.LcmpEF
	bne	cr7,.LcmpGH

.Ltail:
	ld	r31,-8(r1)
	ld	r30,-16(r1)
	ld	r29,-24(r1)
	ld	r28,-32(r1)
	ld	r27,-40(r1)

	cmpdi	r5,0
	beq	.Lzero
	b	.Lshort

.Lfirst32:
	cmpld	cr1,rC,rD
	cmpld	cr6,rE,rF
	cmpld	cr7,rG,rH

	bne	cr0,.LcmpAB
	bne	cr1,.LcmpCD
	bne	cr6,.LcmpEF
	bne	cr7,.LcmpGH

	b	.Ltail

.LcmpAB:
	li	r3,1
	bgt	cr0,.Lout
	li	r3,-1
	b	.Lout

.LcmpCD:
	li	r3,1
	bgt	cr1,.Lout
	li	r3,-1
	b	.Lout

.LcmpEF:
	li	r3,1
	bgt	cr6,.Lout
	li	r3,-1
	b	.Lout

.LcmpGH:
	li	r3,1
	bgt	cr7,.Lout
	li	r3,-1

.Lout:
	ld	r31,-8(r1)
	ld	r30,-16(r1)
	ld	r29,-24(r1)
	ld	r28,-32(r1)
	ld	r27,-40(r1)
	blr

.LcmpAB_lightweight:   /* skip NV GPRS restore */
	li	r3,1
	bgtlr
	li	r3,-1
	blr

#ifdef CONFIG_ALTIVEC
.Lsameoffset_vmx_cmp:
	/* Enter with src/dst addrs has the same offset with 8 bytes
	 * align boundary.
	 *
	 * There is an optimization based on following fact: memcmp()
	 * prones to fail early at the first 32 bytes.
	 * Before applying VMX instructions which will lead to 32x128bits
	 * VMX regs load/restore penalty, we compare the first 32 bytes
	 * so that we can catch the ~80% fail cases.
	 */

	li	r0,4
	mtctr	r0
.Lsameoffset_prechk_32B_loop:
	LD	rA,0,r3
	LD	rB,0,r4
	cmpld	cr0,rA,rB
	addi	r3,r3,8
	addi	r4,r4,8
	bne     cr0,.LcmpAB_lightweight
	addi	r5,r5,-8
	bdnz	.Lsameoffset_prechk_32B_loop

	ENTER_VMX_OPS
	beq     cr1,.Llong_novmx_cmp

3:
	/* need to check whether r4 has the same offset with r3
	 * for 16 bytes boundary.
	 */
	xor	r0,r3,r4
	andi.	r0,r0,0xf
	bne	.Ldiffoffset_vmx_cmp_start

	/* len is no less than 4KB. Need to align with 16 bytes further.
	 */
	andi.	rA,r3,8
	LD	rA,0,r3
	beq	4f
	LD	rB,0,r4
	cmpld	cr0,rA,rB
	addi	r3,r3,8
	addi	r4,r4,8
	addi	r5,r5,-8

	beq	cr0,4f
	/* save and restore cr0 */
	mfocrf  r5,128
	EXIT_VMX_OPS
	mtocrf  128,r5
	b	.LcmpAB_lightweight

4:
	/* compare 32 bytes for each loop */
	srdi	r0,r5,5
	mtctr	r0
	clrldi  r5,r5,59
	li	off16,16

.balign 16
5:
	lvx 	v0,0,r3
	lvx 	v1,0,r4
	VCMPEQUD_RC(v0,v0,v1)
	bnl	cr6,7f
	lvx 	v0,off16,r3
	lvx 	v1,off16,r4
	VCMPEQUD_RC(v0,v0,v1)
	bnl	cr6,6f
	addi	r3,r3,32
	addi	r4,r4,32
	bdnz	5b

	EXIT_VMX_OPS
	cmpdi	r5,0
	beq	.Lzero
	b	.Lcmp_lt32bytes

6:
	addi	r3,r3,16
	addi	r4,r4,16

7:
	/* diff the last 16 bytes */
	EXIT_VMX_OPS
	LD	rA,0,r3
	LD	rB,0,r4
	cmpld	cr0,rA,rB
	li	off8,8
	bne	cr0,.LcmpAB_lightweight

	LD	rA,off8,r3
	LD	rB,off8,r4
	cmpld	cr0,rA,rB
	bne	cr0,.LcmpAB_lightweight
	b	.Lzero
#endif

.Ldiffoffset_8bytes_make_align_start:
	/* now try to align s1 with 8 bytes */
	rlwinm  r6,r3,3,26,28
	beq     .Ldiffoffset_align_s1_8bytes

	clrrdi	r3,r3,3
	LD	rA,0,r3
	LD	rB,0,r4  /* unaligned load */
	sld	rA,rA,r6
	srd	rA,rA,r6
	srd	rB,rB,r6
	cmpld	cr0,rA,rB
	srwi	r6,r6,3
	bne	cr0,.LcmpAB_lightweight

	subfic  r6,r6,8
	subf.	r5,r6,r5
	addi	r3,r3,8
	add	r4,r4,r6

	beq	.Lzero

.Ldiffoffset_align_s1_8bytes:
	/* now s1 is aligned with 8 bytes. */
#ifdef CONFIG_ALTIVEC
BEGIN_FTR_SECTION
	/* only do vmx ops when the size equal or greater than 4K bytes */
	cmpdi	cr5,r5,VMX_THRESH
	bge	cr5,.Ldiffoffset_vmx_cmp
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)

.Ldiffoffset_novmx_cmp:
#endif


	cmpdi   cr5,r5,31
	ble	cr5,.Lcmp_lt32bytes

#ifdef CONFIG_ALTIVEC
	b	.Llong_novmx_cmp
#else
	b	.Llong
#endif

#ifdef CONFIG_ALTIVEC
.Ldiffoffset_vmx_cmp:
	/* perform a 32 bytes pre-checking before
	 * enable VMX operations.
	 */
	li	r0,4
	mtctr	r0
.Ldiffoffset_prechk_32B_loop:
	LD	rA,0,r3
	LD	rB,0,r4
	cmpld	cr0,rA,rB
	addi	r3,r3,8
	addi	r4,r4,8
	bne     cr0,.LcmpAB_lightweight
	addi	r5,r5,-8
	bdnz	.Ldiffoffset_prechk_32B_loop

	ENTER_VMX_OPS
	beq     cr1,.Ldiffoffset_novmx_cmp

.Ldiffoffset_vmx_cmp_start:
	/* Firstly try to align r3 with 16 bytes */
	andi.   r6,r3,0xf
	li	off16,16
	beq     .Ldiffoffset_vmx_s1_16bytes_align

	LVS	v3,0,r3
	LVS	v4,0,r4

	lvx     v5,0,r3
	lvx     v6,0,r4
	LD_VSR_CROSS16B(r3,v3,v5,v7,v9)
	LD_VSR_CROSS16B(r4,v4,v6,v8,v10)

	VCMPEQUB_RC(v7,v9,v10)
	bnl	cr6,.Ldiffoffset_vmx_diff_found

	subfic  r6,r6,16
	subf    r5,r6,r5
	add     r3,r3,r6
	add     r4,r4,r6

.Ldiffoffset_vmx_s1_16bytes_align:
	/* now s1 is aligned with 16 bytes */
	lvx     v6,0,r4
	LVS	v4,0,r4
	srdi	r6,r5,5  /* loop for 32 bytes each */
	clrldi  r5,r5,59
	mtctr	r6

.balign	16
.Ldiffoffset_vmx_32bytesloop:
	/* the first qw of r4 was saved in v6 */
	lvx	v9,0,r3
	LD_VSR_CROSS16B(r4,v4,v6,v8,v10)
	VCMPEQUB_RC(v7,v9,v10)
	vor	v6,v8,v8
	bnl	cr6,.Ldiffoffset_vmx_diff_found

	addi	r3,r3,16
	addi	r4,r4,16

	lvx	v9,0,r3
	LD_VSR_CROSS16B(r4,v4,v6,v8,v10)
	VCMPEQUB_RC(v7,v9,v10)
	vor	v6,v8,v8
	bnl	cr6,.Ldiffoffset_vmx_diff_found

	addi	r3,r3,16
	addi	r4,r4,16

	bdnz	.Ldiffoffset_vmx_32bytesloop

	EXIT_VMX_OPS

	cmpdi	r5,0
	beq	.Lzero
	b	.Lcmp_lt32bytes

.Ldiffoffset_vmx_diff_found:
	EXIT_VMX_OPS
	/* anyway, the diff will appear in next 16 bytes */
	li	r5,16
	b	.Lcmp_lt32bytes

#endif
EXPORT_SYMBOL(memcmp)