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change in opcode OP_LOADNIL: B is used as a counter instead of a

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register. (Avoids an assignment to R(B), not present in any other
instruction.)
This commit is contained in:
Roberto Ierusalimschy
2011-04-19 13:22:13 -03:00
parent a4e644add2
commit 4758113043
5 changed files with 22 additions and 18 deletions
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18
lcode.c
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@@ -1,5 +1,5 @@
/*
** $Id: lcode.c,v 2.51 2011/02/01 18:03:10 roberto Exp roberto $
** $Id: lcode.c,v 2.52 2011/04/07 18:14:12 roberto Exp roberto $
** Code generator for Lua
** See Copyright Notice in lua.h
*/
@@ -35,19 +35,23 @@ static int isnumeral(expdesc *e) {
void luaK_nil (FuncState *fs, int from, int n) {
Instruction *previous;
int l = from + n - 1; /* last register to set nil */
if (fs->pc > fs->lasttarget) { /* no jumps to current position? */
previous = &fs->f->code[fs->pc-1];
if (GET_OPCODE(*previous) == OP_LOADNIL) {
int pfrom = GETARG_A(*previous);
int pto = GETARG_B(*previous);
if (pfrom <= from && from <= pto+1) { /* can connect both? */
if (from+n-1 > pto)
SETARG_B(*previous, from+n-1);
int pl = pfrom + GETARG_B(*previous);
if ((pfrom <= from && from <= pl + 1) ||
(from <= pfrom && pfrom <= l + 1)) { /* can connect both? */
if (pfrom < from) from = pfrom; /* from = min(from, pfrom) */
if (pl > l) l = pl; /* l = max(l, pl) */
SETARG_A(*previous, from);
SETARG_B(*previous, l - from);
return;
}
}
} /* else go through */
}
luaK_codeABC(fs, OP_LOADNIL, from, from+n-1, 0); /* else no optimization */
luaK_codeABC(fs, OP_LOADNIL, from, n - 1, 0); /* else no optimization */
}