From 7aa3031ebaa5dc641808f55cb1cb27ddc409fbca Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Wed, 6 Aug 2014 15:46:33 -0400 Subject: [PATCH] cmd/gc: make liveness ~10x faster MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 1) The arrayindexof lookup function is O(n). Replace with O(1) lookups. 2) The checkptxt function is O(n²) and is purely for debugging. Only run when the debugging flags are turned on. 3) Iterating over sparse bitmaps can be done faster word by word. Introduce and use bvnext for that. Run times before and after, on my 2.5 GHz Core i5 MacBook Pro. x.go 9.48 0.84 issue 8259 x100.go 0.01 0.01 issue 8354 x1000.go 0.10 0.10 x2000.go 0.62 0.19 x3000.go 1.33 0.34 x4000.go 2.29 0.49 x5000.go 3.89 0.67 x6000.go 5.00 0.90 x7000.go 6.70 1.13 x8000.go 9.44 1.38 x9000.go 11.23 1.87 x10000.go 13.78 2.09 Fixes #8259. Fixes #8354. LGTM=iant, r R=golang-codereviews, iant, r CC=golang-codereviews https://golang.org/cl/125720043 --- src/cmd/gc/array.c | 14 ------------- src/cmd/gc/bv.c | 36 ++++++++++++++++++++++++++------ src/cmd/gc/go.h | 2 +- src/cmd/gc/plive.c | 52 +++++++++++++++++++++++++++++++++------------- 4 files changed, 69 insertions(+), 35 deletions(-) diff --git a/src/cmd/gc/array.c b/src/cmd/gc/array.c index 5e53c1ff0e2e6..611fc9fbd406d 100644 --- a/src/cmd/gc/array.c +++ b/src/cmd/gc/array.c @@ -108,20 +108,6 @@ arrayadd(Array *array, void *element) arrayset(array, array->length - 1, element); } -int32 -arrayindexof(Array *array, void *element) -{ - void *p; - int32 i; - - for(i = 0; i < array->length; i++) { - p = arrayget(array, i); - if(memcmp(p, &element, array->size) == 0) - return i; - } - return -1; -} - void arraysort(Array *array, int (*cmp)(const void*, const void*)) { diff --git a/src/cmd/gc/bv.c b/src/cmd/gc/bv.c index 2efbbc565e338..0e8f8d4739477 100644 --- a/src/cmd/gc/bv.c +++ b/src/cmd/gc/bv.c @@ -9,6 +9,8 @@ enum { WORDSIZE = sizeof(uint32), WORDBITS = 32, + WORDMASK = WORDBITS - 1, + WORDSHIFT = 5, }; static uintptr @@ -94,13 +96,35 @@ bvconcat(Bvec *src1, Bvec *src2) int bvget(Bvec *bv, int32 i) { - uint32 mask, word; - if(i < 0 || i >= bv->n) fatal("bvget: index %d is out of bounds with length %d\n", i, bv->n); - mask = 1U << (i % WORDBITS); - word = bv->b[i / WORDBITS] & mask; - return word ? 1 : 0; + return (bv->b[i>>WORDSHIFT] >> (i&WORDMASK)) & 1; +} + +// bvnext returns the smallest index >= i for which bvget(bv, i) == 1. +// If there is no such index, bvnext returns -1. +int +bvnext(Bvec *bv, int32 i) +{ + uint32 w; + + // Jump i ahead to next word with bits. + if((bv->b[i>>WORDSHIFT]>>(i&WORDMASK)) == 0) { + i &= ~WORDMASK; + i += WORDBITS; + while(i < bv->n && bv->b[i>>WORDSHIFT] == 0) + i += WORDBITS; + } + if(i >= bv->n) + return -1; + + // Find 1 bit. + w = bv->b[i>>WORDSHIFT]>>(i&WORDMASK); + while((w&1) == 0) { + w>>=1; + i++; + } + return i; } int @@ -109,7 +133,7 @@ bvisempty(Bvec *bv) int32 i; for(i = 0; i < bv->n; i += WORDBITS) - if(bv->b[i / WORDBITS] != 0) + if(bv->b[i>>WORDSHIFT] != 0) return 0; return 1; } diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h index 30b210f92e57d..c3da5f636a388 100644 --- a/src/cmd/gc/go.h +++ b/src/cmd/gc/go.h @@ -1017,7 +1017,6 @@ int32 arraylength(Array *array); void* arrayget(Array *array, int32 index); void arrayset(Array *array, int32 index, void *element); void arrayadd(Array *array, void *element); -int32 arrayindexof(Array* array, void *element); void arraysort(Array* array, int (*cmp)(const void*, const void*)); /* @@ -1043,6 +1042,7 @@ int bvcmp(Bvec *bv1, Bvec *bv2); void bvcopy(Bvec *dst, Bvec *src); Bvec* bvconcat(Bvec *src1, Bvec *src2); int bvget(Bvec *bv, int32 i); +int32 bvnext(Bvec *bv, int32 i); int bvisempty(Bvec *bv); void bvnot(Bvec *bv); void bvor(Bvec *dst, Bvec *src1, Bvec *src2); diff --git a/src/cmd/gc/plive.c b/src/cmd/gc/plive.c index 9026f6003e81b..e67b0af757b48 100644 --- a/src/cmd/gc/plive.c +++ b/src/cmd/gc/plive.c @@ -283,13 +283,30 @@ getvariables(Node *fn) // For arguments and results, the bitmap covers all variables, // so we must include all the variables, even the ones without // pointers. + // + // The Node.opt field is available for use by optimization passes. + // We use it to hold the index of the node in the variables array, plus 1 + // (so that 0 means the Node is not in the variables array). + // Each pass should clear opt when done, but you never know, + // so clear them all ourselves too. + // The Node.curfn field is supposed to be set to the current function + // already, but for some compiler-introduced names it seems not to be, + // so fix that here. + // Later, when we want to find the index of a node in the variables list, + // we will check that n->curfn == curfn and n->opt > 0. Then n->opt - 1 + // is the index in the variables list. + ll->n->opt = nil; + ll->n->curfn = curfn; switch(ll->n->class) { case PAUTO: - if(haspointers(ll->n->type)) + if(haspointers(ll->n->type)) { + ll->n->opt = (void*)(uintptr)(arraylength(result)+1); arrayadd(result, &ll->n); + } break; case PPARAM: case PPARAMOUT: + ll->n->opt = (void*)(uintptr)(arraylength(result)+1); arrayadd(result, &ll->n); break; } @@ -718,14 +735,16 @@ progeffects(Prog *prog, Array *vars, Bvec *uevar, Bvec *varkill, Bvec *avarinit) } if(info.flags & (LeftRead | LeftWrite | LeftAddr)) { from = &prog->from; - if (from->node != nil && from->sym != nil) { + if (from->node != nil && from->sym != nil && from->node->curfn == curfn) { switch(from->node->class & ~PHEAP) { case PAUTO: case PPARAM: case PPARAMOUT: - pos = arrayindexof(vars, from->node); + pos = (int)(uintptr)from->node->opt - 1; // index in vars if(pos == -1) goto Next; + if(pos >= arraylength(vars) || *(Node**)arrayget(vars, pos) != from->node) + fatal("bad bookkeeping in liveness %N %d", from->node, pos); if(from->node->addrtaken) { bvset(avarinit, pos); } else { @@ -741,14 +760,16 @@ progeffects(Prog *prog, Array *vars, Bvec *uevar, Bvec *varkill, Bvec *avarinit) Next: if(info.flags & (RightRead | RightWrite | RightAddr)) { to = &prog->to; - if (to->node != nil && to->sym != nil) { + if (to->node != nil && to->sym != nil && to->node->curfn == curfn) { switch(to->node->class & ~PHEAP) { case PAUTO: case PPARAM: case PPARAMOUT: - pos = arrayindexof(vars, to->node); + pos = (int)(uintptr)to->node->opt - 1; // index in vars if(pos == -1) goto Next1; + if(pos >= arraylength(vars) || *(Node**)arrayget(vars, pos) != to->node) + fatal("bad bookkeeping in liveness %N %d", to->node, pos); if(to->node->addrtaken) { if(prog->as != AVARKILL) bvset(avarinit, pos); @@ -1020,6 +1041,9 @@ checkptxt(Node *fn, Prog *firstp) { Prog *p; + if(debuglive == 0) + return; + for(p = firstp; p != P; p = p->link) { if(0) print("analyzing '%P'\n", p); @@ -1172,21 +1196,17 @@ twobitlivepointermap(Liveness *lv, Bvec *liveout, Array *vars, Bvec *args, Bvec vlong xoffset; int32 i; - for(i = 0; i < arraylength(vars); i++) { + for(i = 0; (i = bvnext(liveout, i)) >= 0; i++) { node = *(Node**)arrayget(vars, i); switch(node->class) { case PAUTO: - if(bvget(liveout, i)) { - xoffset = node->xoffset + stkptrsize; - twobitwalktype1(node->type, &xoffset, locals); - } + xoffset = node->xoffset + stkptrsize; + twobitwalktype1(node->type, &xoffset, locals); break; case PPARAM: case PPARAMOUT: - if(bvget(liveout, i)) { - xoffset = node->xoffset; - twobitwalktype1(node->type, &xoffset, args); - } + xoffset = node->xoffset; + twobitwalktype1(node->type, &xoffset, args); break; } } @@ -1944,6 +1964,7 @@ liveness(Node *fn, Prog *firstp, Sym *argssym, Sym *livesym) Array *cfg, *vars; Liveness *lv; int debugdelta; + NodeList *l; // Change name to dump debugging information only for a specific function. debugdelta = 0; @@ -1984,6 +2005,9 @@ liveness(Node *fn, Prog *firstp, Sym *argssym, Sym *livesym) twobitwritesymbol(lv->argslivepointers, argssym); // Free everything. + for(l=fn->dcl; l != nil; l = l->next) + if(l->n != N) + l->n->opt = nil; freeliveness(lv); arrayfree(vars); freecfg(cfg);