Fix IA-64 memchr read-ahead.

The latest stratcliff extension exposed a bug in the IA-64 memchr which
uses non-speculative loads to prefetch data.  Change the code to use
speculative loads with appropriate fixup.  Fixes BZ 10162.

diff --git a/ChangeLog b/ChangeLog
index 5746edee2403f5fe912b21bdf93847736cf80c5a..4247797ee81e0c77dfcbc5828dbe732b3614b2e4 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-05-21  H.J. Lu  <hongjiu.lu@intel.com>
+
+       [BZ #10162]
+       * sysdeps/ia64/memchr.S: Use speculative load.
+
 2009-05-21  H.J. Lu  <hongjiu.lu@intel.com>
 
        * sysdeps/unix/sysv/linux/ia64/____longjmp_chk.S: New file.

diff --git a/sysdeps/ia64/memchr.S b/sysdeps/ia64/memchr.S
index e9a7ba823049ad03ce449c41af837433298e8142..cd062b2dd521c5777d805cbf07bbd78060f17299 100644 (file)
--- a/sysdeps/ia64/memchr.S
+++ b/sysdeps/ia64/memchr.S
@@ -96,7 +96,8 @@ ENTRY(__memchr)
        mov     pr.rot = 1 << 16 ;;
 .l2:
 (p[0])         mov     addr[0] = ret0
-(p[0])         ld8     value[0] = [ret0], 8
+(p[0])         ld8.s   value[0] = [ret0], 8     // speculative load
+(p[MEMLAT])    chk.s   value[MEMLAT], .recovery // check and recovery
 (p[MEMLAT])    xor     aux[0] = value[MEMLAT], chrx8
 (p[MEMLAT+1])  czx1.r  poschr[0] = aux[1]
 (p[MEMLAT+2])  cmp.ne  p7, p0 = 8, poschr[1]
@@ -124,6 +125,20 @@ ENTRY(__memchr)
        mov     ar.lc = saved_lc
        br.ret.sptk.many b0
 
+.recovery:
+       adds    ret0 = -((MEMLAT + 1) * 8), ret0;;
+(p[MEMLAT+1])  add     ret0 = -8, ret0;;
+(p[MEMLAT+2])  add     ret0 = -8, ret0;;
+.l4:
+       mov     addr[MEMLAT+2] = ret0
+       ld8     tmp = [ret0];;          // load the first unchecked 8byte
+       xor     aux[1] = tmp, chrx8;;
+       czx1.r  poschr[1] = aux[1];;
+       cmp.ne  p7, p0 = 8, poschr[1]
+(p7)   br.cond.spnt    .foundit;;
+       adds    ret0 = 8, ret0          // load the next unchecked 8byte
+       br.sptk .l4;;
+
 END(__memchr)
 
 weak_alias (__memchr, memchr)