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new optimization: jumps to jumps

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Roberto Ierusalimschy
2000-04-06 14:36:52 -03:00
parent c6965ce551
commit d615e78e08
3 changed files with 38 additions and 23 deletions
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22
lcode.c
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@@ -1,5 +1,5 @@
/*
** $Id: lcode.c,v 1.19 2000/04/04 20:48:44 roberto Exp roberto $
** $Id: lcode.c,v 1.20 2000/04/05 17:51:58 roberto Exp roberto $
** Code generator for Lua
** See Copyright Notice in lua.h
*/
@@ -171,7 +171,12 @@ static void luaK_neq (FuncState *fs) {
int luaK_jump (FuncState *fs) {
return luaK_S(fs, OP_JMP, NO_JUMP, 0);
int j = luaK_S(fs, OP_JMP, NO_JUMP, 0);
if (j == fs->lasttarget) { /* possible jumps to this jump? */
luaK_concat(fs, &j, fs->jlt); /* keep them on hold */
fs->jlt = NO_JUMP;
}
return j;
}
@@ -220,11 +225,17 @@ static int luaK_getjump (FuncState *fs, int pc) {
/*
** discharge list of jumps to last target.
** returns current `pc' and marks it as a jump target (to avoid wrong
** optimizations with consecutive instructions not in the same basic block).
*/
int luaK_getlabel (FuncState *fs) {
fs->lasttarget = fs->pc;
if (fs->pc != fs->lasttarget) {
int lasttarget = fs->lasttarget;
fs->lasttarget = fs->pc;
luaK_patchlist(fs, fs->jlt, lasttarget); /* discharge old list `jlt' */
fs->jlt = NO_JUMP; /* nobody jumps to this new label (till now) */
}
return fs->pc;
}
@@ -394,7 +405,10 @@ static void luaK_patchlistaux (FuncState *fs, int list, int target,
void luaK_patchlist (FuncState *fs, int list, int target) {
luaK_patchlistaux(fs, list, target, OP_END, 0);
if (target == fs->lasttarget) /* same target that list `jlt'? */
luaK_concat(fs, &fs->jlt, list); /* delay fixing */
else
luaK_patchlistaux(fs, list, target, OP_END, 0);
}