DrSocalkwe3n/luajit
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Improve alias analysis of upvalues using a disambiguation hash value.

Browse Source 
All upvalue objects hold a disambiguation hash value now.
It's built from the parent prototype and the slot number.
Different hash values imply the upvalues cannot alias.
Same hash values don't imply anything (collision or different closures).
Upvalue disambiguation makes use of a reduced hash due to IR contraints.
This commit is contained in:
Mike Pall
2010-01-09 23:59:43 +01:00
parent 2cc554db0c
commit 99d153bef9
7 changed files with 32 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
src/lj_record.c
View File

@@ -781,6 +781,15 @@ static TRef rec_idx(jit_State *J, RecordIndex *ix)
/* -- Upvalue access ------------------------------------------------------ */
/* Shrink disambiguation hash into an 8 bit value. */
static uint32_t shrink_dhash(uint32_t lo, uint32_t hi)
{
lo ^= hi; hi = lj_rol(hi, 14);
lo -= hi; hi = lj_rol(hi, 5);
hi ^= lo; hi -= lj_rol(lo, 27);
return (hi & 0xff);
}
/* Record upvalue load/store. */
static TRef rec_upvalue(jit_State *J, uint32_t uv, TRef val)
{
@@ -788,6 +797,8 @@ static TRef rec_upvalue(jit_State *J, uint32_t uv, TRef val)
TRef fn = getcurrf(J);
IRRef uref;
int needbarrier = 0;
/* Note: this effectively limits LJ_MAX_UPVAL to 127. */
uv = (uv << 8) | shrink_dhash(uvp->dhash, uvp->dhash-0x04c11db7);
if (!uvp->closed) {
/* In current stack? */
if (uvval(uvp) >= J->L->stack && uvval(uvp) < J->L->maxstack) {