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| author | Quentin Carbonneaux <quentin@c9x.me> | 2019-05-02 20:26:16 +0200 |
|---|---|---|
| committer | Quentin Carbonneaux <quentin@c9x.me> | 2019-05-02 20:31:39 +0200 |
| commit | 2e7d6b24eaa1314eb4fe663ef5dc529e461fb8ce (patch) | |
| tree | 1e5a0857b5581f3c214515f7cecc86467c148a7c | |
| parent | 4b7f02c09710b379a706708ae5880a1811519539 (diff) | |
| download | roux-2e7d6b24eaa1314eb4fe663ef5dc529e461fb8ce.tar.gz | |
revert heuristic to reuse stack slots
The heuristic was bogus for at least
two reasons (see below), and, looking
at some generated code, it looks like
some other issues are more pressing.
1. A stack slot of 4 bytes could be
used for a temporary of 8 bytes.
2. Should 2 arguments of an operation
end up spilled, the same slot
could be allocated to both!
| -rw-r--r-- | spill.c | 16 |
1 files changed, 2 insertions, 14 deletions
diff --git a/spill.c b/spill.c index 0742caa..c1599c0 100644 --- a/spill.c +++ b/spill.c @@ -309,7 +309,7 @@ void spill(Fn *fn) { Blk *b, *s1, *s2, *hd, **bp; - int j, l, t, k, s, lvarg[2]; + int j, l, t, k, lvarg[2]; uint n; BSet u[1], v[1], w[1]; Ins *i; @@ -404,11 +404,9 @@ spill(Fn *fn) continue; } bszero(w); - s = -1; if (!req(i->to, R)) { assert(rtype(i->to) == RTmp); t = i->to.val; - s = tmp[t].slot; if (bshas(v, t)) bsclr(v, t); else { @@ -442,13 +440,6 @@ spill(Fn *fn) bsset(v, t); if (j-- <= 0) bsset(w, t); - else if (!lvarg[n]) { - /* recycle the slot of - * i->to when possible - */ - if (tmp[t].slot == -1) - tmp[t].slot = s; - } break; } bscopy(u, v); @@ -456,10 +447,7 @@ spill(Fn *fn) for (n=0; n<2; n++) if (rtype(i->arg[n]) == RTmp) { t = i->arg[n].val; - if (bshas(v, t)) { - if (tmp[t].slot == s) - tmp[t].slot = -1; - } else { + if (!bshas(v, t)) { /* do not reload if the * argument is dead */ |