PowerPC LE memchr and memrchr

http://sourceware.org/ml/libc-alpha/2013-08/msg00105.html

Like strnlen, memchr and memrchr had a number of defects fixed by this
patch as well as adding little-endian support.  The first one I
noticed was that the entry to the main loop needlessly checked for
"are we done yet?" when we know the size is large enough that we can't
be done.  The second defect I noticed was that the main loop count was
wrong, which in turn meant that the small loop needed to handle an
extra word.  Thirdly, there is nothing to say that the string can't
wrap around zero, except of course that we'd normally hit a segfault
on trying to read from address zero.  Fixing that simplified a number
of places:

-	/* Are we done already?  */
-	addi    r9,r8,8
-	cmpld	r9,r7
-	bge	L(null)

becomes

+	cmpld	r8,r7
+	beqlr

However, the exit gets an extra test because I test for being on the
last word then if so whether the byte offset is less than the end.
Overall, the change is a win.

Lastly, memrchr used the wrong cache hint.

	* sysdeps/powerpc/powerpc64/power7/memchr.S: Replace rlwimi with
	insrdi.  Make better use of reg selection to speed exit slightly.
	Schedule entry path a little better.  Remove useless "are we done"
	checks on entry to main loop.  Handle wrapping around zero address.
	Correct main loop count.  Handle single left-over word from main
	loop inline rather than by using loop_small.  Remove extra word
	case in loop_small caused by wrong loop count.  Add little-endian
	support.
	* sysdeps/powerpc/powerpc32/power7/memchr.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/memrchr.S: Likewise.  Use proper
	cache hint.
	* sysdeps/powerpc/powerpc32/power7/memrchr.S: Likewise.
	* sysdeps/powerpc/powerpc64/power7/rawmemchr.S: Add little-endian
	support.  Avoid rlwimi.
	* sysdeps/powerpc/powerpc32/power7/rawmemchr.S: Likewise.

1 files changed, 14 insertions, 3 deletions

diff --git a/sysdeps/powerpc/powerpc64/power7/rawmemchr.S b/sysdeps/powerpc/powerpc64/power7/rawmemchr.S
index 50a33d8fae..547aed771f 100644
--- a/sysdeps/powerpc/powerpc64/power7/rawmemchr.S
+++ b/sysdeps/powerpc/powerpc64/power7/rawmemchr.S
@@ -27,8 +27,8 @@ ENTRY (__rawmemchr)
 	clrrdi	r8,r3,3	      /* Align the address to doubleword boundary.  */
 
 	/* Replicate byte to doubleword.  */
-	rlwimi	r4,r4,8,16,23
-	rlwimi	r4,r4,16,0,15
+	insrdi	r4,r4,8,48
+	insrdi	r4,r4,16,32
 	insrdi	r4,r4,32,0
 
 	/* Now r4 has a doubleword of c bytes.  */
@@ -36,8 +36,13 @@ ENTRY (__rawmemchr)
 	rlwinm	r6,r3,3,26,28 /* Calculate padding.  */
 	ld	r12,0(r8)     /* Load doubleword from memory.  */
 	cmpb	r5,r12,r4     /* Compare each byte against c byte.  */
+#ifdef __LITTLE_ENDIAN__
+	srd	r5,r5,r6
+	sld	r5,r5,r6
+#else
 	sld	r5,r5,r6      /* Move left to discard ignored bits.  */
 	srd	r5,r5,r6      /* Bring the bits back as zeros.  */
+#endif
 	cmpdi	cr7,r5,0      /* If r5 == 0, no c bytes have been found.  */
 	bne	cr7,L(done)
 
@@ -91,8 +96,14 @@ L(loop):
 	   doubleword from the string.  Use that fact to find out what is
 	   the position of the byte inside the string.  */
 L(done):
+#ifdef __LITTLE_ENDIAN__
+	addi    r0,r5,-1
+	andc    r0,r0,r5
+	popcntd	r0,r0	      /* Count trailing zeros.  */
+#else
 	cntlzd	r0,r5	      /* Count leading zeros before the match.  */
-	srdi	r0,r0,3	      /* Convert leading zeroes to bytes.  */
+#endif
+	srdi	r0,r0,3	      /* Convert leading zeros to bytes.  */
 	add	r3,r8,r0      /* Return address of the matching char.  */
 	blr
 END (__rawmemchr)