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Small optimizations in range checks

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Checks of the form '1 <= x && x <= M' were rewritten in the form
'(unsigned)x - 1 < (unsigned)M', which is usually more efficient.
(Other similar checks have similar translations.) Although
some compilers do these optimizations, that does not happen
for all compilers or all cases.
This commit is contained in:
Roberto Ierusalimschy
2019-03-27 14:56:10 -03:00
parent 0443ad9e28
commit d12262068d
4 changed files with 20 additions and 11 deletions
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10
lapi.c
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@@ -936,8 +936,8 @@ LUA_API int lua_setiuservalue (lua_State *L, int idx, int n) {
api_checknelems(L, 1);
o = index2value(L, idx);
api_check(L, ttisfulluserdata(o), "full userdata expected");
if (!(0 < n && n <= uvalue(o)->nuvalue))
res = 0;
if (!(cast_uint(n) - 1u < cast_uint(uvalue(o)->nuvalue)))
res = 0; /* 'n' not in [1, uvalue(o)->nuvalue] */
else {
setobj(L, &uvalue(o)->uv[n - 1].uv, s2v(L->top - 1));
luaC_barrierback(L, gcvalue(o), s2v(L->top - 1));
@@ -1313,7 +1313,8 @@ static const char *aux_upvalue (TValue *fi, int n, TValue **val,
switch (ttypetag(fi)) {
case LUA_TCCL: { /* C closure */
CClosure *f = clCvalue(fi);
if (!(1 <= n && n <= f->nupvalues)) return NULL;
if (!(cast_uint(n) - 1u < cast_uint(f->nupvalues)))
return NULL; /* 'n' not in [1, f->nupvalues] */
*val = &f->upvalue[n-1];
if (owner) *owner = obj2gco(f);
return "";
@@ -1322,7 +1323,8 @@ static const char *aux_upvalue (TValue *fi, int n, TValue **val,
LClosure *f = clLvalue(fi);
TString *name;
Proto *p = f->p;
if (!(1 <= n && n <= p->sizeupvalues)) return NULL;
if (!(cast_uint(n) - 1u < cast_uint(p->sizeupvalues)))
return NULL; /* 'n' not in [1, p->sizeupvalues] */
*val = f->upvals[n-1]->v;
if (owner) *owner = obj2gco(f->upvals[n - 1]);
name = p->upvalues[n-1].name;