Backport of

    commit 72607db038df1a1a7987af814aad8d2ed466c45c

    Author: Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>

    Date:   Fri Jan 9 11:56:35 2015 -0500

        powerpc: Optimize POWER7 strcmp trailing checks

        This patch optimized the POWER7 trailing check by avoiding using byte

        read operations and instead use the doubleword already readed with

        bitwise operations.

        ChangeLog:

    	2015-01-13  Rajalakshmi Srinivasaraghavan  <raji@linux.vnet.ibm.com>

    		    Adhemerval Zanella  <azanella@linux.vnet.ibm.com>

    	* sysdeps/powerpc/powerpc64/power7/strcmp.S (strcmp): Optimize

    	trailing byte check.

diff --git a/sysdeps/powerpc/powerpc64/power7/strcmp.S b/sysdeps/powerpc/powerpc64/power7/strcmp.S

index f16a9d8..ade2811 100644

--- a/sysdeps/powerpc/powerpc64/power7/strcmp.S

+++ b/sysdeps/powerpc/powerpc64/power7/strcmp.S

@@ -25,122 +25,96 @@

 /* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4])  */

+	.machine	power7

 EALIGN (strcmp, 4, 0)

 	CALL_MCOUNT 2

 	or r9, r3, r4

 	rldicl. r10, r9, 0, 61	/* are s1 and s2 8 byte aligned..?  */

 	bne cr0, L(process_unaligned_bytes)

+	li	r5, 0

+	.align 4

 /* process input parameters on double word aligned boundary  */

-	ld r9, 0(r4)		/* load s2 at offset=0  */

-	li r10, 0		/* load mask=0  */

-	cmpb r10, r9, r10	/* compare bytes at s2 with mask  */

-	cmpdi cr7, r10, 0	/* is NULL found ..? is end of string HIT  */

-	bne cr7, L(process_unaligned_bytes)	/* process byte by byte  */

-

-	ld r10, 0(r3)		/* load s1 at offset=0  */

-	li r8, 0		/* load mask=0  */

-	cmpb r8, r10, r8	/* compare bytes at s1 with mask  */

-	cmpdi cr7, r8, 0	/* is NULL found ..? is end of string HIT  */

-	bne cr7, L(process_unaligned_bytes)	/* process byte by byte  */

-

-/*s1 and s2 does not contain NULL now , so compare all 8 bytes in a GO  */

-	cmpb r9, r10, r9	/* compare s1 and s2  */

-	cmpdi cr7, r9, -1	/* compare result with 0xFFFFFFFFFFFFFFFF  */

-	bne cr7, L(process_unaligned_bytes)	/* s1,s2 mismatch found  */

-

-	addi r5, r3, 8		/* save next offset of s2  */

-	addi r11, r4, 8		/* save next offset of s1  */

-	ld r8, 8(r4)		/* load s2 at offset=8  */

-	li r9, 0		/* load mask=0  */

-	cmpb r9, r8, r9		/* compare bytes at s2 with mask  */

-	cmpdi cr7, r9, 0	/* NULL found ..?  */

-	bne cr7, L(processBytes)/* update input and process bytes one by one  */

-

-	mr r9, r4		/* save s2  */

-	li r10, 0		/* load mask=0  */

-

-	ld r7, 8(r3)		/* load s1 at offset=8  */

-	cmpb r6, r7, r10	/* compare bytes at s1 with mask  */

-	cmpdi cr7, r6, 0	/* is NULL found  */

-	bne cr7, L(processBytes)/* mismatch, so process one by one  */

-

 L(unrollDword):

-	cmpb r8, r7, r8		/* compare s1 and s2  */

-	cmpdi cr7, r8, -1	/* compare result with 0xFFFFFFFFFFFFFFFF  */

-	bne cr7, L(processBytes)/* mismatch with s1 and s2  */

-

-	addi r5, r3, 16		/* save offset=16 of s1  */

-	addi r4, r9, 16		/* save offset=16 of s2  */

-	ld r8, 16(r9)		/* load s2 at offset=16  */

-	cmpb r7, r8, r10	/* compare bytes at s2 with mask  */

-	cmpdi cr7, r7, 0	/* NULL found  ..?  */

-	bne cr7, L(update2processBytes)

-

-	ld r7, 16(r3)		/* load s1 at offset=16  */

-	cmpb r6, r7, r10	/* check s1 for end of string  */

-	cmpdi cr7, r6, 0	/* end of s1 ?,then handle byte by byte  */

-	bne 7,L(update2processBytes)

-

-	cmpb r8, r7, r8		/* compare s1 and s2 double words  */

-	cmpdi cr7, r8, -1	/* compare results with 0xFFFFFFFFFFFFFFFF  */

-	bne cr7,L(update2processBytes)

-

-	addi r5, r3, 24		/* update s1 to offset=24  */

-	addi r4, r9, 24		/* update s2 to offset=24  */

-

-	ld r8, 24(r9)		/* load s2  */

-	cmpb r7, r8, r10	/* compare s2 for NULL  */

-	cmpdi cr7, r7, 0	/* verify if s2 is ending now  */

-	bne cr7,L(update2processBytes)

-

-	ld r7, 24(r3)		/* load s1 at offset=24  */

-	cmpb r6, r7, r10	/* verify for NULL  */

-	cmpdi cr7, r6, 0	/* is NULL found  */

-	bne cr7, L(update2processBytes)

-

-	cmpb r8, r7, r8		/* compare s1 and s2  */

-	cmpdi cr7, r8, -1	/* are s1 and s2 same ..?  */

-	bne cr7, L(update2processBytes)

-

-	addi r7, r9, 32		/* update s2 to next double word  */

-	addi r3, r3, 32		/* update s1 to next double word  */

-

-	ld r8, 32(r9)		/* load s2  */

-	mr r4, r7		/* save s2  */

-	cmpb r6, r8, r10	/* compare s2 with NULL  */

-	cmpdi cr7, r6, 0	/* end of s2 ..? */

-	bne cr7, L(process_unaligned_bytes)

-

-	ld r6, 0(r3)		/* load and compare s1 for NULL  */

-	cmpb r5, r6, r10

-	cmpdi cr7, r5, 0

-	bne cr7, L(process_unaligned_bytes)

-

-	cmpb r8, r6, r8		/* compare s1 and s2  */

-	cmpdi cr7, r8, -1

-	bne cr7, L(process_unaligned_bytes)

-

-	addi r5, r3, 8		/* increment s1 and d2 here  */

-	addi r11, r9, 40

-

-	ld r8, 40(r9)		/* process s2 now  */

-	cmpb r9, r8, r10

-	cmpdi cr7, r9, 0

-	bne cr7, L(processBytes)

-

-	mr r9, r7

-	ld r7, 8(r3)		/* process s1 now  */

-	cmpb r6, r7, r10

-	cmpdi cr7, r6, 0

-	beq cr7, L(unrollDword)	/* unroll to compare s1 and s2  */

-

-L(processBytes):

-	mr r4, r11		/* update input params  */

-	mr r3, r5

-

-	.p2align 4

+	ld	r8,0(r3)

+	ld	r10,0(r4)

+	cmpb	r7,r8,r5

+	cmpdi	cr7,r7,0

+	mr	r9,r7

+	bne 	cr7,L(null_found)

+	cmpld	cr7,r8,r10

+	bne	cr7,L(different)

+

+	ld	r8,8(r3)

+	ld	r10,8(r4)

+	cmpb	r7,r8,r5

+	cmpdi	cr7,r7,0

+	mr	r9,r7

+	bne 	cr7,L(null_found)

+	cmpld	cr7,r8,r10

+	bne	cr7,L(different)

+

+	ld	r8,16(r3)

+	ld	r10,16(r4)

+	cmpb	r7,r8,r5

+	cmpdi	cr7,r7,0

+	mr	r9,r7

+	bne 	cr7,L(null_found)

+	cmpld	cr7,r8,r10

+	bne	cr7,L(different)

+

+	ld	r8,24(r3)

+	ld	r10,24(r4)

+	cmpb	r7,r8,r5

+	cmpdi	cr7,r7,0

+	mr	r9,r7

+	bne 	cr7,L(null_found)

+	cmpld	cr7,r8,r10

+	bne	cr7,L(different)

+

+	addi r3, r3, 32

+	addi r4, r4, 32

+	beq cr7, L(unrollDword)

+

+	.align 4

+L(null_found):

+#ifdef __LITTLE_ENDIAN__

+	neg	r7,r9

+	and	r9,r9,r7

+	li	r7,-1

+	cntlzd	r9,r9

+	subfic	r9,r9,71

+	sld	r9,r7,r9

+#else

+	cntlzd	r9,r9

+	li	r7,-1

+	addi	r9,r9,8

+	srd	r9,r7,r9

+#endif

+	or	r8,r8,r9

+	or	r10,r10,r9

+

+L(different):

+	cmpb	r9,r8,r10

+#ifdef __LITTLE_ENDIAN__

+	addi	r7,r9,1

+	andc	r9,r7,r9

+	cntlzd	r9,r9

+	subfic	r9,r9,63

+#else

+	not	r9,r9

+	cntlzd	r9,r9

+	subfic	r9,r9,56

+#endif

+	srd	r3,r8,r9

+	srd	r10,r10,r9

+	rldicl	r10,r10,0,56

+	rldicl	r3,r3,0,56

+	subf	r3,r10,r3

+	blr

+

+	.align 4

 L(process_unaligned_bytes):

 	lbz r9, 0(r3)		/* load byte from s1  */

 	lbz r10, 0(r4)		/* load byte from s2  */

@@ -172,24 +146,19 @@ L(process_unaligned_bytes):

 	addi r4, r4, 4		/* increment s2 by unroll factor  */

 	beq cr6, L(process_unaligned_bytes)	/* unroll byte processing  */

-	.p2align 4

+	.align 4

 L(ComputeDiff):

 	extsw r9, r9

 	subf r10, r10, r9	/* compute s1 - s2  */

 	extsw r3, r10

 	blr			/* return  */

-	.p2align 4

+	.align 4

 L(diffOfNULL):

 	li r9, 0

 	subf r10, r10, r9	/* compute s1 - s2  */

 	extsw r3, r10		/* sign extend result  */

 	blr			/* return  */

-	.p2align 4

-L(update2processBytes):

-	mr r3, r5		/* update and proceed  */

-	b L(process_unaligned_bytes)

-

 END (strcmp)

 libc_hidden_builtin_def (strcmp)