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Fixed small issue with constant propagation

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Constants directly assigned to other constants were not propagating:
For instance, in
  local <const> k1 = 10
  local <const> k2 = k1
'k2' were not treated as a compile-time constant.
This commit is contained in:
Roberto Ierusalimschy 2019-07-17 14:50:42 -03:00
parent d6af81084d
commit 8082906c05
2 changed files with 21 additions and 7 deletions
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18
lcode.c
View File

@ -67,6 +67,15 @@ static int tonumeral (const expdesc *e, TValue *v) {
} }
/*
** Get the constant value from a constant expression
*/
static TValue *const2val (FuncState *fs, const expdesc *e) {
lua_assert(e->k == VCONST);
return &fs->ls->dyd->actvar.arr[e->u.info].k;
}
/* /*
** If expression is a constant, fills 'v' with its value ** If expression is a constant, fills 'v' with its value
** and returns 1. Otherwise, returns 0. ** and returns 1. Otherwise, returns 0.
@ -85,6 +94,10 @@ int luaK_exp2const (FuncState *fs, const expdesc *e, TValue *v) {
setsvalue(fs->ls->L, v, e->u.strval); setsvalue(fs->ls->L, v, e->u.strval);
return 1; return 1;
} }
case VCONST: {
setobj(fs->ls->L, v, const2val(fs, e));
return 1;
}
default: return tonumeral(e, v); default: return tonumeral(e, v);
} }
} }
@ -730,14 +743,13 @@ void luaK_setoneret (FuncState *fs, expdesc *e) {
/* /*
** Ensure that expression 'e' is not a variable. ** Ensure that expression 'e' is not a variable (nor a constant).
** (Expression still may have jump lists.) ** (Expression still may have jump lists.)
*/ */
void luaK_dischargevars (FuncState *fs, expdesc *e) { void luaK_dischargevars (FuncState *fs, expdesc *e) {
switch (e->k) { switch (e->k) {
case VCONST: { case VCONST: {
TValue *val = &fs->ls->dyd->actvar.arr[e->u.info].k; const2exp(const2val(fs, e), e);
const2exp(val, e);
break; break;
} }
case VLOCAL: { /* already in a register */ case VLOCAL: { /* already in a register */

10
testes/code.lua
View File

@ -8,7 +8,8 @@ end
print "testing code generation and optimizations" print "testing code generation and optimizations"
-- to test constant propagation -- to test constant propagation
local <const> k0 = 0 local <const> k0aux = 0
local <const> k0 = k0aux
local <const> k1 = 1 local <const> k1 = 1
local <const> k3 = 3 local <const> k3 = 3
local <const> k6 = k3 + (k3 << k0) local <const> k6 = k3 + (k3 << k0)
@ -410,8 +411,9 @@ checkequal(function () return 6 and true or nil end,
do -- string constants do -- string constants
local <const> k0 = "00000000000000000000000000000000000000000000000000"
local function f1 () local function f1 ()
local <const> k = "00000000000000000000000000000000000000000000000000" local <const> k = k0
return function () return function ()
return function () return k end return function () return k end
end end
@ -419,8 +421,8 @@ do -- string constants
local f2 = f1() local f2 = f1()
local f3 = f2() local f3 = f2()
assert(f3() == string.rep("0", 50)) assert(f3() == k0)
checkK(f3, f3()) checkK(f3, k0)
-- string is not needed by other functions -- string is not needed by other functions
assert(T.listk(f1)[1] == nil) assert(T.listk(f1)[1] == nil)
assert(T.listk(f2)[1] == nil) assert(T.listk(f2)[1] == nil)