From 7e26dc8d0fe0c3c6da511fb9fb1b66a4eaa3a32c Mon Sep 17 00:00:00 2001 From: Dibyendu Majumdar Date: Wed, 1 Jul 2020 22:34:38 +0100 Subject: [PATCH] issue #195 number and integer comparisons --- src/lvm.c | 105 ++++++++++++++++++++++++++++++++++-------------------- 1 file changed, 66 insertions(+), 39 deletions(-) diff --git a/src/lvm.c b/src/lvm.c index 110edcf..9df8183 100644 --- a/src/lvm.c +++ b/src/lvm.c @@ -526,8 +526,8 @@ void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) { /* -** Compare two strings 'ls' x 'rs', returning an integer smaller-equal- -** -larger than zero if 'ls' is smaller-equal-larger than 'rs'. +** Compare two strings 'ls' x 'rs', returning an integer less-equal- +** -greater than zero if 'ls' is less-equal-greater than 'rs'. ** The code is a little tricky because it allows '\0' in the strings ** and it uses 'strcoll' (to respect locales) for each segments ** of the strings. @@ -546,7 +546,7 @@ static int l_strcmp (const TString *ls, const TString *rs) { if (len == lr) /* 'rs' is finished? */ return (len == ll) ? 0 : 1; /* check 'ls' */ else if (len == ll) /* 'ls' is finished? */ - return -1; /* 'ls' is smaller than 'rs' ('rs' is not finished) */ + return -1; /* 'ls' is less than 'rs' ('rs' is not finished) */ /* both strings longer than 'len'; go on comparing after the '\0' */ len++; l += len; ll -= len; r += len; lr -= len; @@ -558,25 +558,24 @@ static int l_strcmp (const TString *ls, const TString *rs) { /* ** Check whether integer 'i' is less than float 'f'. If 'i' has an ** exact representation as a float ('l_intfitsf'), compare numbers as -** floats. Otherwise, if 'f' is outside the range for integers, result -** is trivial. Otherwise, compare them as integers. (When 'i' has no -** float representation, either 'f' is "far away" from 'i' or 'f' has -** no precision left for a fractional part; either way, how 'f' is -** truncated is irrelevant.) When 'f' is NaN, comparisons must result -** in false. +** floats. Otherwise, use the equivalence 'i < f <=> i < ceil(f)'. +** If 'ceil(f)' is out of integer range, either 'f' is greater than +** all integers or less than all integers. +** (The test with 'l_intfitsf' is only for performance; the else +** case is correct for all values, but it is slow due to the conversion +** from float to int.) +** When 'f' is NaN, comparisons must result in false. */ static int LTintfloat (lua_Integer i, lua_Number f) { -#if defined(l_intfitsf) - if (!l_intfitsf(i)) { - if (f >= -cast_num(LUA_MININTEGER)) /* -minint == maxint + 1 */ - return 1; /* f >= maxint + 1 > i */ - else if (f > cast_num(LUA_MININTEGER)) /* minint < f <= maxint ? */ - return (i < cast(lua_Integer, f)); /* compare them as integers */ - else /* f <= minint <= i (or 'f' is NaN) --> not(i < f) */ - return 0; + if (l_intfitsf(i)) + return luai_numlt(cast_num(i), f); /* compare them as floats */ + else { /* i < f <=> i < ceil(f) */ + lua_Integer fi; + if (luaV_flttointeger(f, &fi, F2Iceil)) /* fi = ceil(f) */ + return i < fi; /* compare them as integers */ + else /* 'f' is either greater or less than all integers */ + return f > 0; /* greater? */ } -#endif - return luai_numlt(cast_num(i), f); /* compare them as floats */ } @@ -585,17 +584,49 @@ static int LTintfloat (lua_Integer i, lua_Number f) { ** See comments on previous function. */ static int LEintfloat (lua_Integer i, lua_Number f) { -#if defined(l_intfitsf) - if (!l_intfitsf(i)) { - if (f >= -cast_num(LUA_MININTEGER)) /* -minint == maxint + 1 */ - return 1; /* f >= maxint + 1 > i */ - else if (f >= cast_num(LUA_MININTEGER)) /* minint <= f <= maxint ? */ - return (i <= cast(lua_Integer, f)); /* compare them as integers */ - else /* f < minint <= i (or 'f' is NaN) --> not(i <= f) */ - return 0; + if (l_intfitsf(i)) + return luai_numle(cast_num(i), f); /* compare them as floats */ + else { /* i <= f <=> i <= floor(f) */ + lua_Integer fi; + if (luaV_flttointeger(f, &fi, F2Ifloor)) /* fi = floor(f) */ + return i <= fi; /* compare them as integers */ + else /* 'f' is either greater or less than all integers */ + return f > 0; /* greater? */ + } +} + + +/* +** Check whether float 'f' is less than integer 'i'. +** See comments on previous function. +*/ +static int LTfloatint (lua_Number f, lua_Integer i) { + if (l_intfitsf(i)) + return luai_numlt(f, cast_num(i)); /* compare them as floats */ + else { /* f < i <=> floor(f) < i */ + lua_Integer fi; + if (luaV_flttointeger(f, &fi, F2Ifloor)) /* fi = floor(f) */ + return fi < i; /* compare them as integers */ + else /* 'f' is either greater or less than all integers */ + return f < 0; /* less? */ + } +} + + +/* +** Check whether float 'f' is less than or equal to integer 'i'. +** See comments on previous function. +*/ +static int LEfloatint (lua_Number f, lua_Integer i) { + if (l_intfitsf(i)) + return luai_numle(f, cast_num(i)); /* compare them as floats */ + else { /* f <= i <=> ceil(f) <= i */ + lua_Integer fi; + if (luaV_flttointeger(f, &fi, F2Iceil)) /* fi = ceil(f) */ + return fi <= i; /* compare them as integers */ + else /* 'f' is either greater or less than all integers */ + return f < 0; /* less? */ } -#endif - return luai_numle(cast_num(i), f); /* compare them as floats */ } @@ -615,10 +646,8 @@ static int LTnum (const TValue *l, const TValue *r) { lua_Number lf = fltvalue(l); /* 'l' must be float */ if (ttisfloat(r)) return luai_numlt(lf, fltvalue(r)); /* both are float */ - else if (luai_numisnan(lf)) /* 'r' is int and 'l' is float */ - return 0; /* NaN < i is always false */ - else /* without NaN, (l < r) <--> not(r <= l) */ - return !LEintfloat(ivalue(r), lf); /* not (r <= l) ? */ + else /* 'l' is float and 'r' is int */ + return LTfloatint(lf, ivalue(r)); } } @@ -639,10 +668,8 @@ static int LEnum (const TValue *l, const TValue *r) { lua_Number lf = fltvalue(l); /* 'l' must be float */ if (ttisfloat(r)) return luai_numle(lf, fltvalue(r)); /* both are float */ - else if (luai_numisnan(lf)) /* 'r' is int and 'l' is float */ - return 0; /* NaN <= i is always false */ - else /* without NaN, (l <= r) <--> not(r < l) */ - return !LTintfloat(ivalue(r), lf); /* not (r < l) ? */ + else /* 'l' is float and 'r' is int */ + return LEfloatint(lf, ivalue(r)); } } @@ -785,7 +812,7 @@ void luaV_concat (lua_State *L, int total) { /* collect total length and number of strings */ for (n = 1; n < total && tostring(L, top - n - 1); n++) { size_t l = vslen(top - n - 1); - if (l >= (MAX_SIZE/sizeof(char)) - tl) + if (unlikely(l >= (MAX_SIZE/sizeof(char)) - tl)) luaG_runerror(L, "string length overflow"); tl += l; } @@ -835,7 +862,7 @@ void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) { } default: { /* try metamethod */ tm = luaT_gettmbyobj(L, rb, TM_LEN); - if (ttisnil(tm)) /* no metamethod? */ + if (unlikely(ttisnil(tm))) /* no metamethod? */ luaG_typeerror(L, rb, "get length of"); break; }