--- /dev/null
+/*
+ *
+ * Optimized version of the standard memcpy() function
+ *
+ * Inputs:
+ * in0: destination address
+ * in1: source address
+ * in2: number of bytes to copy
+ * Output:
+ * no return value
+ *
+ * Copyright (C) 2000-2001 Hewlett-Packard Co
+ * Stephane Eranian <eranian@hpl.hp.com>
+ * David Mosberger-Tang <davidm@hpl.hp.com>
+ */
+#include <asm/asmmacro.h>
+
+GLOBAL_ENTRY(memcpy)
+
+# define MEM_LAT 21 /* latency to memory */
+
+# define dst r2
+# define src r3
+# define retval r8
+# define saved_pfs r9
+# define saved_lc r10
+# define saved_pr r11
+# define cnt r16
+# define src2 r17
+# define t0 r18
+# define t1 r19
+# define t2 r20
+# define t3 r21
+# define t4 r22
+# define src_end r23
+
+# define N (MEM_LAT + 4)
+# define Nrot ((N + 7) & ~7)
+
+ /*
+ * First, check if everything (src, dst, len) is a multiple of eight. If
+ * so, we handle everything with no taken branches (other than the loop
+ * itself) and a small icache footprint. Otherwise, we jump off to
+ * the more general copy routine handling arbitrary
+ * sizes/alignment etc.
+ */
+ .prologue
+ .save ar.pfs, saved_pfs
+ alloc saved_pfs=ar.pfs,3,Nrot,0,Nrot
+ .save ar.lc, saved_lc
+ mov saved_lc=ar.lc
+ or t0=in0,in1
+ ;;
+
+ or t0=t0,in2
+ .save pr, saved_pr
+ mov saved_pr=pr
+
+ .body
+
+ cmp.eq p6,p0=in2,r0 // zero length?
+ mov retval=in0 // return dst
+(p6) br.ret.spnt.many rp // zero length, return immediately
+ ;;
+
+ mov dst=in0 // copy because of rotation
+ shr.u cnt=in2,3 // number of 8-byte words to copy
+ mov pr.rot=1<<16
+ ;;
+
+ adds cnt=-1,cnt // br.ctop is repeat/until
+ cmp.gtu p7,p0=16,in2 // copying less than 16 bytes?
+ mov ar.ec=N
+ ;;
+
+ and t0=0x7,t0
+ mov ar.lc=cnt
+ ;;
+ cmp.ne p6,p0=t0,r0
+
+ mov src=in1 // copy because of rotation
+(p7) br.cond.spnt.few .memcpy_short
+(p6) br.cond.spnt.few .memcpy_long
+ ;;
+ nop.m 0
+ ;;
+ nop.m 0
+ nop.i 0
+ ;;
+ nop.m 0
+ ;;
+ .rotr val[N]
+ .rotp p[N]
+ .align 32
+1: { .mib
+(p[0]) ld8 val[0]=[src],8
+ nop.i 0
+ brp.loop.imp 1b, 2f
+}
+2: { .mfb
+(p[N-1])st8 [dst]=val[N-1],8
+ nop.f 0
+ br.ctop.dptk.few 1b
+}
+ ;;
+ mov ar.lc=saved_lc
+ mov pr=saved_pr,-1
+ mov ar.pfs=saved_pfs
+ br.ret.sptk.many rp
+
+ /*
+ * Small (<16 bytes) unaligned copying is done via a simple byte-at-the-time
+ * copy loop. This performs relatively poorly on Itanium, but it doesn't
+ * get used very often (gcc inlines small copies) and due to atomicity
+ * issues, we want to avoid read-modify-write of entire words.
+ */
+ .align 32
+.memcpy_short:
+ adds cnt=-1,in2 // br.ctop is repeat/until
+ mov ar.ec=MEM_LAT
+ brp.loop.imp 1f, 2f
+ ;;
+ mov ar.lc=cnt
+ ;;
+ nop.m 0
+ ;;
+ nop.m 0
+ nop.i 0
+ ;;
+ nop.m 0
+ ;;
+ nop.m 0
+ ;;
+ /*
+ * It is faster to put a stop bit in the loop here because it makes
+ * the pipeline shorter (and latency is what matters on short copies).
+ */
+ .align 32
+1: { .mib
+(p[0]) ld1 val[0]=[src],1
+ nop.i 0
+ brp.loop.imp 1b, 2f
+} ;;
+2: { .mfb
+(p[MEM_LAT-1])st1 [dst]=val[MEM_LAT-1],1
+ nop.f 0
+ br.ctop.dptk.few 1b
+} ;;
+ mov ar.lc=saved_lc
+ mov pr=saved_pr,-1
+ mov ar.pfs=saved_pfs
+ br.ret.sptk.many rp
+
+ /*
+ * Large (>= 16 bytes) copying is done in a fancy way. Latency isn't
+ * an overriding concern here, but throughput is. We first do
+ * sub-word copying until the destination is aligned, then we check
+ * if the source is also aligned. If so, we do a simple load/store-loop
+ * until there are less than 8 bytes left over and then we do the tail,
+ * by storing the last few bytes using sub-word copying. If the source
+ * is not aligned, we branch off to the non-congruent loop.
+ *
+ * stage: op:
+ * 0 ld
+ * :
+ * MEM_LAT+3 shrp
+ * MEM_LAT+4 st
+ *
+ * On Itanium, the pipeline itself runs without stalls. However, br.ctop
+ * seems to introduce an unavoidable bubble in the pipeline so the overall
+ * latency is 2 cycles/iteration. This gives us a _copy_ throughput
+ * of 4 byte/cycle. Still not bad.
+ */
+# undef N
+# undef Nrot
+# define N (MEM_LAT + 5) /* number of stages */
+# define Nrot ((N+1 + 2 + 7) & ~7) /* number of rotating regs */
+
+#define LOG_LOOP_SIZE 6
+
+.memcpy_long:
+ alloc t3=ar.pfs,3,Nrot,0,Nrot // resize register frame
+ and t0=-8,src // t0 = src & ~7
+ and t2=7,src // t2 = src & 7
+ ;;
+ ld8 t0=[t0] // t0 = 1st source word
+ adds src2=7,src // src2 = (src + 7)
+ sub t4=r0,dst // t4 = -dst
+ ;;
+ and src2=-8,src2 // src2 = (src + 7) & ~7
+ shl t2=t2,3 // t2 = 8*(src & 7)
+ shl t4=t4,3 // t4 = 8*(dst & 7)
+ ;;
+ ld8 t1=[src2] // t1 = 1st source word if src is 8-byte aligned, 2nd otherwise
+ sub t3=64,t2 // t3 = 64-8*(src & 7)
+ shr.u t0=t0,t2
+ ;;
+ add src_end=src,in2
+ shl t1=t1,t3
+ mov pr=t4,0x38 // (p5,p4,p3)=(dst & 7)
+ ;;
+ or t0=t0,t1
+ mov cnt=r0
+ adds src_end=-1,src_end
+ ;;
+(p3) st1 [dst]=t0,1
+(p3) shr.u t0=t0,8
+(p3) adds cnt=1,cnt
+ ;;
+(p4) st2 [dst]=t0,2
+(p4) shr.u t0=t0,16
+(p4) adds cnt=2,cnt
+ ;;
+(p5) st4 [dst]=t0,4
+(p5) adds cnt=4,cnt
+ and src_end=-8,src_end // src_end = last word of source buffer
+ ;;
+
+ // At this point, dst is aligned to 8 bytes and there at least 16-7=9 bytes left to copy:
+
+1:{ add src=cnt,src // make src point to remainder of source buffer
+ sub cnt=in2,cnt // cnt = number of bytes left to copy
+ mov t4=ip
+ } ;;
+ and src2=-8,src // align source pointer
+ adds t4=.memcpy_loops-1b,t4
+ mov ar.ec=N
+
+ and t0=7,src // t0 = src & 7
+ shr.u t2=cnt,3 // t2 = number of 8-byte words left to copy
+ shl cnt=cnt,3 // move bits 0-2 to 3-5
+ ;;
+
+ .rotr val[N+1], w[2]
+ .rotp p[N]
+
+ cmp.ne p6,p0=t0,r0 // is src aligned, too?
+ shl t0=t0,LOG_LOOP_SIZE // t0 = 8*(src & 7)
+ adds t2=-1,t2 // br.ctop is repeat/until
+ ;;
+ add t4=t0,t4
+ mov pr=cnt,0x38 // set (p5,p4,p3) to # of bytes last-word bytes to copy
+ mov ar.lc=t2
+ ;;
+ nop.m 0
+ ;;
+ nop.m 0
+ nop.i 0
+ ;;
+ nop.m 0
+ ;;
+(p6) ld8 val[1]=[src2],8 // prime the pump...
+ mov b6=t4
+ br.sptk.few b6
+ ;;
+
+.memcpy_tail:
+ // At this point, (p5,p4,p3) are set to the number of bytes left to copy (which is
+ // less than 8) and t0 contains the last few bytes of the src buffer:
+(p5) st4 [dst]=t0,4
+(p5) shr.u t0=t0,32
+ mov ar.lc=saved_lc
+ ;;
+(p4) st2 [dst]=t0,2
+(p4) shr.u t0=t0,16
+ mov ar.pfs=saved_pfs
+ ;;
+(p3) st1 [dst]=t0
+ mov pr=saved_pr,-1
+ br.ret.sptk.many rp
+
+///////////////////////////////////////////////////////
+ .align 64
+
+#define COPY(shift,index) \
+ 1: { .mib \
+ (p[0]) ld8 val[0]=[src2],8; \
+ (p[MEM_LAT+3]) shrp w[0]=val[MEM_LAT+3],val[MEM_LAT+4-index],shift; \
+ brp.loop.imp 1b, 2f \
+ }; \
+ 2: { .mfb \
+ (p[MEM_LAT+4]) st8 [dst]=w[1],8; \
+ nop.f 0; \
+ br.ctop.dptk.few 1b; \
+ }; \
+ ;; \
+ ld8 val[N-1]=[src_end]; /* load last word (may be same as val[N]) */ \
+ ;; \
+ shrp t0=val[N-1],val[N-index],shift; \
+ br .memcpy_tail
+.memcpy_loops:
+ COPY(0, 1) /* no point special casing this---it doesn't go any faster without shrp */
+ COPY(8, 0)
+ COPY(16, 0)
+ COPY(24, 0)
+ COPY(32, 0)
+ COPY(40, 0)
+ COPY(48, 0)
+ COPY(56, 0)
+
+END(memcpy)
Code Review / kvmfornfv.git / blobdiff