Abstract out pointer hash to hashrot(). Tune hash constants.

1 files changed, 1 insertions, 10 deletions

diff --git a/src/lj_record.c b/src/lj_record.c
index 55daaae6..9355cb38 100644
--- a/src/lj_record.c
+++ b/src/lj_record.c
@@ -1051,15 +1051,6 @@ 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)
 {
@@ -1068,7 +1059,7 @@ static TRef rec_upvalue(jit_State *J, uint32_t uv, TRef val)
   IRRef uref;
   int needbarrier = 0;
   /* Note: this effectively limits LJ_MAX_UPVAL to 127. */
-  uv = (uv << 8) | shrink_dhash(uvp->dhash, uvp->dhash-0x04c11db7);
+  uv = (uv << 8) | (hashrot(uvp->dhash, uvp->dhash + HASH_BIAS) & 0xff);
   if (!uvp->closed) {
     /* In current stack? */
     if (uvval(uvp) >= J->L->stack && uvval(uvp) < J->L->maxstack) {