[release-branch.go1.3] cmd/gc: make liveness ~10x faster
««« CL 125720043 / b92e5df7d3ba
cmd/gc: make liveness ~10x faster
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
»»»
TBR=rsc
CC=golang-codereviews
https://golang.org/cl/121600043
diff --git a/src/cmd/gc/array.c b/src/cmd/gc/array.c
index 5e53c1f..611fc9f 100644
--- a/src/cmd/gc/array.c
+++ b/src/cmd/gc/array.c
@@ -108,20 +108,6 @@
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 2efbbc5..0e8f8d4 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 @@
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 @@
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 413e710..ee879f6 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -1017,7 +1017,6 @@
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 @@
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 eb89017..7a40ab5 100644
--- a/src/cmd/gc/plive.c
+++ b/src/cmd/gc/plive.c
@@ -283,13 +283,30 @@
// 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 @@
}
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 @@
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 @@
{
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 @@
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;
}
}
@@ -1937,6 +1957,7 @@
Array *cfg, *vars;
Liveness *lv;
int debugdelta;
+ NodeList *l;
// Change name to dump debugging information only for a specific function.
debugdelta = 0;
@@ -1977,6 +1998,9 @@
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);
