diff options
| -rw-r--r-- | ChangeLog.alpha | 3 | ||||
| -rw-r--r-- | sysdeps/alpha/strncmp.S | 251 |
2 files changed, 144 insertions, 110 deletions
diff --git a/ChangeLog.alpha b/ChangeLog.alpha index d291df970a..824083c323 100644 --- a/ChangeLog.alpha +++ b/ChangeLog.alpha @@ -1,5 +1,8 @@ 2012-06-06 Richard Henderson <rth@twiddle.net> + * sysdeps/alpha/strncmp.S: Bound count to LONG_MAX at startup. + Re-organize checks vs s2 end-of-count. + [BZ #13718] * sysdeps/alpha/stxncmp.S: Bound count to LONG_MAX at startup. * sysdeps/alpha/alphaev6/stxncmp.S: Likewise. diff --git a/sysdeps/alpha/strncmp.S b/sysdeps/alpha/strncmp.S index c9981e1b66..828f1b9703 100644 --- a/sysdeps/alpha/strncmp.S +++ b/sysdeps/alpha/strncmp.S @@ -1,4 +1,4 @@ -/* Copyright (C) 1996, 1997, 2003 Free Software Foundation, Inc. +/* Copyright (C) 1996-2012 Free Software Foundation, Inc. Contributed by Richard Henderson (rth@tamu.edu) This file is part of the GNU C Library. @@ -23,6 +23,15 @@ .set noat .set noreorder +/* EV6 only predicts one branch per octaword. We'll use these to push + subsequent branches back to the next bundle. This will generally add + a fetch+decode cycle to older machines, so skip in that case. */ +#ifdef __alpha_fix__ +# define ev6_unop unop +#else +# define ev6_unop +#endif + .text ENTRY(strncmp) @@ -35,128 +44,140 @@ ENTRY(strncmp) .prologue 0 #endif - xor a0, a1, t2 # e0 : are s1 and s2 co-aligned? - beq a2, $zerolength # .. e1 : - ldq_u t0, 0(a0) # e0 : give cache time to catch up - ldq_u t1, 0(a1) # .. e1 : - and t2, 7, t2 # e0 : - and a0, 7, t4 # .. e1 : find s1 misalignment - lda t3, -1 # e0 : - addq a2, t4, a2 # .. e1 : bias count by s1 misalignment - and a2, 7, t10 # e1 : ofs of last byte in last word - srl a2, 3, a2 # .. e0 : remaining full words in count - and a1, 7, t5 # e0 : find s2 misalignment - bne t2, $unaligned # .. e1 : + xor a0, a1, t2 # are s1 and s2 co-aligned? + beq a2, $zerolength + ldq_u t0, 0(a0) # load asap to give cache time to catch up + ldq_u t1, 0(a1) + lda t3, -1 + and t2, 7, t2 + srl t3, 1, t6 + and a0, 7, t4 # find s1 misalignment + and a1, 7, t5 # find s2 misalignment + cmovlt a2, t6, a2 # bound neg count to LONG_MAX + addq a1, a2, a3 # s2+count + addq a2, t4, a2 # bias count by s1 misalignment + and a2, 7, t10 # ofs of last byte in s1 last word + srl a2, 3, a2 # remaining full words in s1 count + bne t2, $unaligned /* On entry to this basic block: t0 == the first word of s1. t1 == the first word of s2. t3 == -1. */ - $aligned: - mskqh t3, a1, t3 # e0 : mask off leading garbage - nop # .. e1 : - ornot t1, t3, t1 # e0 : - ornot t0, t3, t0 # .. e1 : - cmpbge zero, t1, t7 # e0 : bits set iff null found - beq a2, $eoc # .. e1 : check end of count - unop # e0 : - bne t7, $eos # .. e1 : - unop # e0 : - beq t10, $ant_loop # .. e1 : + mskqh t3, a1, t8 # mask off leading garbage + ornot t1, t8, t1 + ornot t0, t8, t0 + cmpbge zero, t1, t7 # bits set iff null found + beq a2, $eoc # check end of count + bne t7, $eos + beq t10, $ant_loop /* Aligned compare main loop. On entry to this basic block: t0 == an s1 word. t1 == an s2 word not containing a null. */ + .align 4 $a_loop: xor t0, t1, t2 # e0 : bne t2, $wordcmp # .. e1 (zdb) ldq_u t1, 8(a1) # e0 : ldq_u t0, 8(a0) # .. e1 : + subq a2, 1, a2 # e0 : addq a1, 8, a1 # .. e1 : addq a0, 8, a0 # e0 : beq a2, $eoc # .. e1 : + cmpbge zero, t1, t7 # e0 : beq t7, $a_loop # .. e1 : - unop # e0 : - br $eos # .. e1 : + + br $eos /* Alternate aligned compare loop, for when there's no trailing bytes on the count. We have to avoid reading too much data. */ + .align 4 $ant_loop: xor t0, t1, t2 # e0 : + ev6_unop + ev6_unop bne t2, $wordcmp # .. e1 (zdb) + subq a2, 1, a2 # e0 : beq a2, $zerolength # .. e1 : ldq_u t1, 8(a1) # e0 : ldq_u t0, 8(a0) # .. e1 : + addq a1, 8, a1 # e0 : addq a0, 8, a0 # .. e1 : cmpbge zero, t1, t7 # e0 : beq t7, $ant_loop # .. e1 : - unop # e0 : - br $eos # .. e1 : + + br $eos /* The two strings are not co-aligned. Align s1 and cope. */ + /* On entry to this basic block: + t0 == the first word of s1. + t1 == the first word of s2. + t3 == -1. + t4 == misalignment of s1. + t5 == misalignment of s2. + t10 == misalignment of s1 end. */ + .align 4 $unaligned: - subq a1, t4, a1 # e0 : - unop # : - - /* If s2 misalignment is larger than s2 misalignment, we need + /* If s1 misalignment is larger than s2 misalignment, we need extra startup checks to avoid SEGV. */ + subq a1, t4, a1 # adjust s2 for s1 misalignment + cmpult t4, t5, t9 + subq a3, 1, a3 # last byte of s2 + bic a1, 7, t8 + mskqh t3, t5, t7 # mask garbage in s2 + subq a3, t8, a3 + ornot t1, t7, t7 + srl a3, 3, a3 # remaining full words in s2 count + beq t9, $u_head + + /* Failing that, we need to look for both eos and eoc within the + first word of s2. If we find either, we can continue by + pretending that the next word of s2 is all zeros. */ + lda t2, 0 # next = zero + cmpeq a3, 0, t8 # eoc in the first word of s2? + cmpbge zero, t7, t7 # eos in the first word of s2? + or t7, t8, t8 + bne t8, $u_head_nl - cmplt t4, t5, t8 # .. e1 : - beq t8, $u_head # e1 : - - mskqh t3, t5, t3 # e0 : - ornot t1, t3, t3 # e0 : - cmpbge zero, t3, t7 # e1 : is there a zero? - beq t7, $u_head # e1 : - - /* We've found a zero in the first partial word of s2. Align - our current s1 and s2 words and compare what we've got. */ - - extql t1, t5, t1 # e0 : - lda t3, -1 # .. e1 : - insql t1, a0, t1 # e0 : - mskqh t3, a0, t3 # e0 : - ornot t1, t3, t1 # e0 : - ornot t0, t3, t0 # .. e1 : - cmpbge zero, t1, t7 # e0 : find that zero again - beq a2, $eoc # .. e1 : and finish up - br $eos # e1 : - - .align 3 -$u_head: /* We know just enough now to be able to assemble the first full word of s2. We can still find a zero at the end of it. On entry to this basic block: t0 == first word of s1 - t1 == first partial word of s2. */ - - ldq_u t2, 8(a1) # e0 : load second partial s2 word - lda t3, -1 # .. e1 : create leading garbage mask - extql t1, a1, t1 # e0 : create first s2 word - mskqh t3, a0, t3 # e0 : - extqh t2, a1, t4 # e0 : - ornot t0, t3, t0 # .. e1 : kill s1 garbage - or t1, t4, t1 # e0 : s2 word now complete - ornot t1, t3, t1 # e1 : kill s2 garbage - cmpbge zero, t0, t7 # e0 : find zero in first s1 word - beq a2, $eoc # .. e1 : - lda t3, -1 # e0 : - bne t7, $eos # .. e1 : - subq a2, 1, a2 # e0 : - xor t0, t1, t4 # .. e1 : compare aligned words - mskql t3, a1, t3 # e0 : mask out s2[1] bits we have seen - bne t4, $wordcmp # .. e1 : - or t2, t3, t3 # e0 : - cmpbge zero, t3, t7 # e1 : find zero in high bits of s2[1] - bne t7, $u_final # e1 : + t1 == first partial word of s2. + t3 == -1. + t10 == ofs of last byte in s1 last word. + t11 == ofs of last byte in s2 last word. */ +$u_head: + ldq_u t2, 8(a1) # load second partial s2 word + subq a3, 1, a3 +$u_head_nl: + extql t1, a1, t1 # create first s2 word + mskqh t3, a0, t8 + extqh t2, a1, t4 + ornot t0, t8, t0 # kill s1 garbage + or t1, t4, t1 # s2 word now complete + cmpbge zero, t0, t7 # find eos in first s1 word + ornot t1, t8, t1 # kill s2 garbage + beq a2, $eoc + subq a2, 1, a2 + bne t7, $eos + mskql t3, a1, t8 # mask out s2[1] bits we have seen + xor t0, t1, t4 # compare aligned words + or t2, t8, t8 + bne t4, $wordcmp + cmpbge zero, t8, t7 # eos in high bits of s2[1]? + cmpeq a3, 0, t8 # eoc in s2[1]? + or t7, t8, t7 + bne t7, $u_final /* Unaligned copy main loop. In order to avoid reading too much, the loop is structured to detect zeros in aligned words from s2. @@ -166,43 +187,54 @@ $u_head: to run as fast as possible. On entry to this basic block: - t2 == the unshifted low-bits from the next s2 word. */ - - .align 3 + t2 == the unshifted low-bits from the next s2 word. + t10 == ofs of last byte in s1 last word. + t11 == ofs of last byte in s2 last word. */ + .align 4 $u_loop: extql t2, a1, t3 # e0 : ldq_u t2, 16(a1) # .. e1 : load next s2 high bits ldq_u t0, 8(a0) # e0 : load next s1 word addq a1, 8, a1 # .. e1 : + addq a0, 8, a0 # e0 : - nop # .. e1 : + subq a3, 1, a3 # .. e1 : extqh t2, a1, t1 # e0 : - cmpbge zero, t0, t7 # .. e1 : find zero in current s1 word + cmpbge zero, t0, t7 # .. e1 : eos in current s1 word + or t1, t3, t1 # e0 : - beq a2, $eoc # .. e1 : check for end of count + beq a2, $eoc # .. e1 : eoc in current s1 word subq a2, 1, a2 # e0 : + cmpbge zero, t2, t4 # .. e1 : eos in s2[1] + + xor t0, t1, t3 # e0 : compare the words + ev6_unop + ev6_unop bne t7, $eos # .. e1 : - xor t0, t1, t4 # e0 : compare the words - bne t4, $wordcmp # .. e1 (zdb) - cmpbge zero, t2, t4 # e0 : find zero in next low bits + + cmpeq a3, 0, t5 # e0 : eoc in s2[1] + ev6_unop + ev6_unop + bne t3, $wordcmp # .. e1 : + + or t4, t5, t4 # e0 : eos or eoc in s2[1]. beq t4, $u_loop # .. e1 (zdb) /* We've found a zero in the low bits of the last s2 word. Get the next s1 word and align them. */ + .align 3 $u_final: - ldq_u t0, 8(a0) # e1 : - extql t2, a1, t1 # .. e0 : - cmpbge zero, t1, t7 # e0 : - bne a2, $eos # .. e1 : + ldq_u t0, 8(a0) + extql t2, a1, t1 + cmpbge zero, t1, t7 + bne a2, $eos /* We've hit end of count. Zero everything after the count and compare whats left. */ - .align 3 $eoc: mskql t0, t10, t0 mskql t1, t10, t1 - unop cmpbge zero, t1, t7 /* We've found a zero somewhere in a word we just read. @@ -210,32 +242,31 @@ $eoc: t0 == s1 word t1 == s2 word t7 == cmpbge mask containing the zero. */ - + .align 3 $eos: - negq t7, t6 # e0 : create bytemask of valid data - and t6, t7, t8 # e1 : - subq t8, 1, t6 # e0 : - or t6, t8, t7 # e1 : - zapnot t0, t7, t0 # e0 : kill the garbage - zapnot t1, t7, t1 # .. e1 : - xor t0, t1, v0 # e0 : and compare - beq v0, $done # .. e1 : + negq t7, t6 # create bytemask of valid data + and t6, t7, t8 + subq t8, 1, t6 + or t6, t8, t7 + zapnot t0, t7, t0 # kill the garbage + zapnot t1, t7, t1 + xor t0, t1, v0 # ... and compare + beq v0, $done /* Here we have two differing co-aligned words in t0 & t1. Bytewise compare them and return (t0 > t1 ? 1 : -1). */ .align 3 $wordcmp: - cmpbge t0, t1, t2 # e0 : comparison yields bit mask of ge - cmpbge t1, t0, t3 # .. e1 : - xor t2, t3, t0 # e0 : bits set iff t0/t1 bytes differ - negq t0, t1 # e1 : clear all but least bit - and t0, t1, t0 # e0 : - lda v0, -1 # .. e1 : - and t0, t2, t1 # e0 : was bit set in t0 > t1? - cmovne t1, 1, v0 # .. e1 (zdb) - + cmpbge t0, t1, t2 # comparison yields bit mask of ge + cmpbge t1, t0, t3 + xor t2, t3, t0 # bits set iff t0/t1 bytes differ + negq t0, t1 # clear all but least bit + and t0, t1, t0 + lda v0, -1 + and t0, t2, t1 # was bit set in t0 > t1? + cmovne t1, 1, v0 $done: - ret # e1 : + ret .align 3 $zerolength: |