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cmd/gc: use escape analysis result for make([]T, constant 

Escape analysis already gives that the underlying array
does not escape but the result was ignored.

Fixes #5484.

R=golang-dev, dave, daniel.morsing
CC=golang-dev
https://golang.org/cl/9662046
This commit is contained in:
Rémy Oudompheng 2013-05-30 08:32:00 +02:00
parent 0b88587d22
commit 2c4b029b75
1 changed files with 24 additions and 7 deletions
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31
src/cmd/gc/walk.c
View File

@ -1246,18 +1246,35 @@ walkexpr(Node **np, NodeList **init)
goto ret;
case OMAKESLICE:
// makeslice(t *Type, nel int64, max int64) (ary []any)
l = n->left;
r = n->right;
if(r == nil)
l = r = safeexpr(l, init);
t = n->type;
fn = syslook("makeslice", 1);
argtype(fn, t->type); // any-1
n = mkcall1(fn, n->type, init,
typename(n->type),
conv(l, types[TINT64]),
conv(r, types[TINT64]));
if(n->esc == EscNone
&& smallintconst(l) && smallintconst(r)
&& mpgetfix(r->val.u.xval) < (1ULL<<16) / t->type->width) {
// var arr [r]T
// n = arr[:l]
t = aindex(r, t->type); // [r]T
var = temp(t);
a = nod(OAS, var, N); // zero temp
typecheck(&a, Etop);
*init = list(*init, a);
r = nod(OSLICE, var, nod(OKEY, N, l)); // arr[:l]
r = conv(r, n->type); // in case n->type is named.
typecheck(&r, Erv);
walkexpr(&r, init);
n = r;
} else {
// makeslice(t *Type, nel int64, max int64) (ary []any)
fn = syslook("makeslice", 1);
argtype(fn, t->type); // any-1
n = mkcall1(fn, n->type, init,
typename(n->type),
conv(l, types[TINT64]),
conv(r, types[TINT64]));
}
goto ret;
case ORUNESTR: