Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 323 insertions, 0 deletions

diff --git a/arch/ia64/lib/do_csum.S b/arch/ia64/lib/do_csum.S
new file mode 100644
index 000000000000..6bec2fc9f5b2
--- /dev/null
+++ b/arch/ia64/lib/do_csum.S
@@ -0,0 +1,323 @@
+/*
+ *
+ * Optmized version of the standard do_csum() function
+ *
+ * Return: a 64bit quantity containing the 16bit Internet checksum
+ *
+ * Inputs:
+ *      in0: address of buffer to checksum (char *)
+ *      in1: length of the buffer (int)
+ *
+ * Copyright (C) 1999, 2001-2002 Hewlett-Packard Co
+ *      Stephane Eranian <eranian@hpl.hp.com>
+ *
+ * 02/04/22     Ken Chen <kenneth.w.chen@intel.com>
+ *              Data locality study on the checksum buffer.
+ *              More optimization cleanup - remove excessive stop bits.
+ * 02/04/08     David Mosberger <davidm@hpl.hp.com>
+ *              More cleanup and tuning.
+ * 01/04/18     Jun Nakajima <jun.nakajima@intel.com>
+ *              Clean up and optimize and the software pipeline, loading two
+ *              back-to-back 8-byte words per loop. Clean up the initialization
+ *              for the loop. Support the cases where load latency = 1 or 2.
+ *              Set CONFIG_IA64_LOAD_LATENCY to 1 or 2 (default).
+ */
+
+#include <asm/asmmacro.h>
+
+//
+// Theory of operations:
+//      The goal is to go as quickly as possible to the point where
+//      we can checksum 16 bytes/loop. Before reaching that point we must
+//      take care of incorrect alignment of first byte.
+//
+//      The code hereafter also takes care of the "tail" part of the buffer
+//      before entering the core loop, if any. The checksum is a sum so it
+//      allows us to commute operations. So we do the "head" and "tail"
+//      first to finish at full speed in the body. Once we get the head and
+//      tail values, we feed them into the pipeline, very handy initialization.
+//
+//      Of course we deal with the special case where the whole buffer fits
+//      into one 8 byte word. In this case we have only one entry in the pipeline.
+//
+//      We use a (LOAD_LATENCY+2)-stage pipeline in the loop to account for
+//      possible load latency and also to accommodate for head and tail.
+//
+//      The end of the function deals with folding the checksum from 64bits
+//      down to 16bits taking care of the carry.
+//
+//      This version avoids synchronization in the core loop by also using a
+//      pipeline for the accumulation of the checksum in resultx[] (x=1,2).
+//
+//       wordx[] (x=1,2)
+//      |---|
+//      |   | 0                 : new value loaded in pipeline
+//      |---|
+//      |   | -                 : in transit data
+//      |---|
+//      |   | LOAD_LATENCY      : current value to add to checksum
+//      |---|
+//      |   | LOAD_LATENCY+1    : previous value added to checksum
+//      |---|                   (previous iteration)
+//
+//      resultx[] (x=1,2)
+//      |---|
+//      |   | 0                 : initial value
+//      |---|
+//      |   | LOAD_LATENCY-1    : new checksum
+//      |---|
+//      |   | LOAD_LATENCY      : previous value of checksum
+//      |---|
+//      |   | LOAD_LATENCY+1    : final checksum when out of the loop
+//      |---|
+//
+//
+//      See RFC1071 "Computing the Internet Checksum" for various techniques for
+//      calculating the Internet checksum.
+//
+// NOT YET DONE:
+//      - Maybe another algorithm which would take care of the folding at the
+//        end in a different manner
+//      - Work with people more knowledgeable than me on the network stack
+//        to figure out if we could not split the function depending on the
+//        type of packet or alignment we get. Like the ip_fast_csum() routine
+//        where we know we have at least 20bytes worth of data to checksum.
+//      - Do a better job of handling small packets.
+//      - Note on prefetching: it was found that under various load, i.e. ftp read/write,
+//        nfs read/write, the L1 cache hit rate is at 60% and L2 cache hit rate is at 99.8%
+//        on the data that buffer points to (partly because the checksum is often preceded by
+//        a copy_from_user()).  This finding indiate that lfetch will not be beneficial since
+//        the data is already in the cache.
+//
+
+#define saved_pfs       r11
+#define hmask           r16
+#define tmask           r17
+#define first1          r18
+#define firstval        r19
+#define firstoff        r20
+#define last            r21
+#define lastval         r22
+#define lastoff         r23
+#define saved_lc        r24
+#define saved_pr        r25
+#define tmp1            r26
+#define tmp2            r27
+#define tmp3            r28
+#define carry1          r29
+#define carry2          r30
+#define first2          r31
+
+#define buf             in0
+#define len             in1
+
+#define LOAD_LATENCY    2       // XXX fix me
+
+#if (LOAD_LATENCY != 1) && (LOAD_LATENCY != 2)
+# error "Only 1 or 2 is supported/tested for LOAD_LATENCY."
+#endif
+
+#define PIPE_DEPTH                      (LOAD_LATENCY+2)
+#define ELD     p[LOAD_LATENCY]         // end of load
+#define ELD_1   p[LOAD_LATENCY+1]       // and next stage
+
+// unsigned long do_csum(unsigned char *buf,long len)
+
+GLOBAL_ENTRY(do_csum)
+        .prologue
+        .save ar.pfs, saved_pfs
+        alloc saved_pfs=ar.pfs,2,16,0,16
+        .rotr word1[4], word2[4],result1[LOAD_LATENCY+2],result2[LOAD_LATENCY+2]
+        .rotp p[PIPE_DEPTH], pC1[2], pC2[2]
+        mov ret0=r0             // in case we have zero length
+        cmp.lt p0,p6=r0,len     // check for zero length or negative (32bit len)
+        ;;
+        add tmp1=buf,len        // last byte's address
+        .save pr, saved_pr
+        mov saved_pr=pr         // preserve predicates (rotation)
+(p6)    br.ret.spnt.many rp     // return if zero or negative length
+
+        mov hmask=-1            // initialize head mask
+        tbit.nz p15,p0=buf,0    // is buf an odd address?
+        and first1=-8,buf       // 8-byte align down address of first1 element
+
+        and firstoff=7,buf      // how many bytes off for first1 element
+        mov tmask=-1            // initialize tail mask
+
+        ;;
+        adds tmp2=-1,tmp1       // last-1
+        and lastoff=7,tmp1      // how many bytes off for last element
+        ;;
+        sub tmp1=8,lastoff      // complement to lastoff
+        and last=-8,tmp2        // address of word containing last byte
+        ;;
+        sub tmp3=last,first1    // tmp3=distance from first1 to last
+        .save ar.lc, saved_lc
+        mov saved_lc=ar.lc      // save lc
+        cmp.eq p8,p9=last,first1        // everything fits in one word ?
+
+        ld8 firstval=[first1],8 // load, ahead of time, "first1" word
+        and tmp1=7, tmp1        // make sure that if tmp1==8 -> tmp1=0
+        shl tmp2=firstoff,3     // number of bits
+        ;;
+(p9)    ld8 lastval=[last]      // load, ahead of time, "last" word, if needed
+        shl tmp1=tmp1,3         // number of bits
+(p9)    adds tmp3=-8,tmp3       // effectively loaded
+        ;;
+(p8)    mov lastval=r0          // we don't need lastval if first1==last
+        shl hmask=hmask,tmp2    // build head mask, mask off [0,first1off[
+        shr.u tmask=tmask,tmp1  // build tail mask, mask off ]8,lastoff]
+        ;;
+        .body
+#define count tmp3
+
+(p8)    and hmask=hmask,tmask   // apply tail mask to head mask if 1 word only
+(p9)    and word2[0]=lastval,tmask      // mask last it as appropriate
+        shr.u count=count,3     // how many 8-byte?
+        ;;
+        // If count is odd, finish this 8-byte word so that we can
+        // load two back-to-back 8-byte words per loop thereafter.
+        and word1[0]=firstval,hmask     // and mask it as appropriate
+        tbit.nz p10,p11=count,0         // if (count is odd)
+        ;;
+(p8)    mov result1[0]=word1[0]
+(p9)    add result1[0]=word1[0],word2[0]
+        ;;
+        cmp.ltu p6,p0=result1[0],word1[0]       // check the carry
+        cmp.eq.or.andcm p8,p0=0,count           // exit if zero 8-byte
+        ;;
+(p6)    adds result1[0]=1,result1[0]
+(p8)    br.cond.dptk .do_csum_exit      // if (within an 8-byte word)
+(p11)   br.cond.dptk .do_csum16         // if (count is even)
+
+        // Here count is odd.
+        ld8 word1[1]=[first1],8         // load an 8-byte word
+        cmp.eq p9,p10=1,count           // if (count == 1)
+        adds count=-1,count             // loaded an 8-byte word
+        ;;
+        add result1[0]=result1[0],word1[1]
+        ;;
+        cmp.ltu p6,p0=result1[0],word1[1]
+        ;;
+(p6)    adds result1[0]=1,result1[0]
+(p9)    br.cond.sptk .do_csum_exit      // if (count == 1) exit
+        // Fall through to caluculate the checksum, feeding result1[0] as
+        // the initial value in result1[0].
+        //
+        // Calculate the checksum loading two 8-byte words per loop.
+        //
+.do_csum16:
+        add first2=8,first1
+        shr.u count=count,1     // we do 16 bytes per loop
+        ;;
+        adds count=-1,count
+        mov carry1=r0
+        mov carry2=r0
+        brp.loop.imp 1f,2f
+        ;;
+        mov ar.ec=PIPE_DEPTH
+        mov ar.lc=count // set lc
+        mov pr.rot=1<<16
+        // result1[0] must be initialized in advance.
+        mov result2[0]=r0
+        ;;
+        .align 32
+1:
+(ELD_1) cmp.ltu pC1[0],p0=result1[LOAD_LATENCY],word1[LOAD_LATENCY+1]
+(pC1[1])adds carry1=1,carry1
+(ELD_1) cmp.ltu pC2[0],p0=result2[LOAD_LATENCY],word2[LOAD_LATENCY+1]
+(pC2[1])adds carry2=1,carry2
+(ELD)   add result1[LOAD_LATENCY-1]=result1[LOAD_LATENCY],word1[LOAD_LATENCY]
+(ELD)   add result2[LOAD_LATENCY-1]=result2[LOAD_LATENCY],word2[LOAD_LATENCY]
+2:
+(p[0])  ld8 word1[0]=[first1],16
+(p[0])  ld8 word2[0]=[first2],16
+        br.ctop.sptk 1b
+        ;;
+        // Since len is a 32-bit value, carry cannot be larger than a 64-bit value.
+(pC1[1])adds carry1=1,carry1    // since we miss the last one
+(pC2[1])adds carry2=1,carry2
+        ;;
+        add result1[LOAD_LATENCY+1]=result1[LOAD_LATENCY+1],carry1
+        add result2[LOAD_LATENCY+1]=result2[LOAD_LATENCY+1],carry2
+        ;;
+        cmp.ltu p6,p0=result1[LOAD_LATENCY+1],carry1
+        cmp.ltu p7,p0=result2[LOAD_LATENCY+1],carry2
+        ;;
+(p6)    adds result1[LOAD_LATENCY+1]=1,result1[LOAD_LATENCY+1]
+(p7)    adds result2[LOAD_LATENCY+1]=1,result2[LOAD_LATENCY+1]
+        ;;
+        add result1[0]=result1[LOAD_LATENCY+1],result2[LOAD_LATENCY+1]
+        ;;
+        cmp.ltu p6,p0=result1[0],result2[LOAD_LATENCY+1]
+        ;;
+(p6)    adds result1[0]=1,result1[0]
+        ;;
+.do_csum_exit:
+        //
+        // now fold 64 into 16 bits taking care of carry
+        // that's not very good because it has lots of sequentiality
+        //
+        mov tmp3=0xffff
+        zxt4 tmp1=result1[0]
+        shr.u tmp2=result1[0],32
+        ;;
+        add result1[0]=tmp1,tmp2
+        ;;
+        and tmp1=result1[0],tmp3
+        shr.u tmp2=result1[0],16
+        ;;
+        add result1[0]=tmp1,tmp2
+        ;;
+        and tmp1=result1[0],tmp3
+        shr.u tmp2=result1[0],16
+        ;;
+        add result1[0]=tmp1,tmp2
+        ;;
+        and tmp1=result1[0],tmp3
+        shr.u tmp2=result1[0],16
+        ;;
+        add ret0=tmp1,tmp2
+        mov pr=saved_pr,0xffffffffffff0000
+        ;;
+        // if buf was odd then swap bytes
+        mov ar.pfs=saved_pfs            // restore ar.ec
+(p15)   mux1 ret0=ret0,@rev             // reverse word
+        ;;
+        mov ar.lc=saved_lc
+(p15)   shr.u ret0=ret0,64-16   // + shift back to position = swap bytes
+        br.ret.sptk.many rp
+
+//      I (Jun Nakajima) wrote an equivalent code (see below), but it was
+//      not much better than the original. So keep the original there so that
+//      someone else can challenge.
+//
+//      shr.u word1[0]=result1[0],32
+//      zxt4 result1[0]=result1[0]
+//      ;;
+//      add result1[0]=result1[0],word1[0]
+//      ;;
+//      zxt2 result2[0]=result1[0]
+//      extr.u word1[0]=result1[0],16,16
+//      shr.u carry1=result1[0],32
+//      ;;
+//      add result2[0]=result2[0],word1[0]
+//      ;;
+//      add result2[0]=result2[0],carry1
+//      ;;
+//      extr.u ret0=result2[0],16,16
+//      ;;
+//      add ret0=ret0,result2[0]
+//      ;;
+//      zxt2 ret0=ret0
+//      mov ar.pfs=saved_pfs             // restore ar.ec
+//      mov pr=saved_pr,0xffffffffffff0000
+//      ;;
+//      // if buf was odd then swap bytes
+//      mov ar.lc=saved_lc
+//(p15) mux1 ret0=ret0,@rev             // reverse word
+//      ;;
+//(p15) shr.u ret0=ret0,64-16   // + shift back to position = swap bytes
+//      br.ret.sptk.many rp
+
+END(do_csum)