lua

commit ba710603811c68fe3a69b3bb98e9038d37489a79
parent 3823fc6c814d20f2b2a0a1e3be8782084440040f
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date:   Fri, 15 Mar 2024 11:23:08 -0300

Removed "bulk operations"

Negligible performance gains don't justify extra complexity.

Diffstat:
M
lgc.c
 | 
36
+++++++-----------------------------
M
ltable.c
 | 
17
++++-------------
M
ltable.h
 | 
18
+++---------------

3 files changed, 14 insertions(+), 57 deletions(-)
diff --git a/lgc.c b/lgc.c
@@ -465,46 +465,24 @@ static void traverseweakvalue (global_State *g, Table *h) {
 }
 
 
-#define BK2(x)	cast(lua_Unsigned, ((x) << 8) | BIT_ISCOLLECTABLE)
-/*
-** Check whether some value in the cell starting at index 'i'
-** is collectable
-*/
-static int checkBulkCollectable (Table *h, unsigned i) {
-  const lua_Unsigned bitscoll = BK2(BK2(BK2(BK2(BK2(BK2(BK2(BK2(~0u))))))));
-  int j;
-  i /= NM;
-  for (j = 0; j < BKSZ; j++) {
-    if (h->array[i].u.bulk[j] & bitscoll)
-      return 1;
-  }
-  return 0;
-}
-
-
 /*
-** Traverse the array part of a table. The traversal is made by cells,
-** only traversing a cell if it has some collectable tag among its tags.
+** Traverse the array part of a table.
 */
 static int traversearray (global_State *g, Table *h) {
   unsigned asize = luaH_realasize(h);
   int marked = 0;  /* true if some object is marked in this traversal */
   unsigned i;
-  for (i = 0; i < asize; i += NM) {  /* traverse array in cells */
-    if (checkBulkCollectable(h, i)) {  /* something to mark in this cell? */
-      unsigned j;
-      for (j = 0; j < NM && i + j < asize; j++) {
-        GCObject *o = gcvalarr(h, i + j);
-        if (o != NULL && iswhite(o)) {
-          marked = 1;
-          reallymarkobject(g, o);
-        }
-      }
+  for (i = 0; i < asize; i++) {
+    GCObject *o = gcvalarr(h, i);
+    if (o != NULL && iswhite(o)) {
+      marked = 1;
+      reallymarkobject(g, o);
     }
   }
   return marked;
 }
 
+
 /*
 ** Traverse an ephemeron table and link it to proper list. Returns true
 ** iff any object was marked during this traversal (which implies that
diff --git a/ltable.c b/ltable.c
@@ -665,7 +665,7 @@ static void reinsertOldSlice (lua_State *L, Table *t, unsigned oldasize,
     int tag = *getArrTag(t, i);
     if (!tagisempty(tag)) {  /* a non-empty entry? */
       TValue aux;
-      farr2val(t, i + 1, tag, &aux);
+      farr2val(t, i + 1, tag, &aux);  /* copy entry into 'aux' */
       luaH_setint(L, t, i + 1, &aux);  /* re-insert it into the table */
     }
   }
@@ -673,21 +673,12 @@ static void reinsertOldSlice (lua_State *L, Table *t, unsigned oldasize,
 }
 
 
-#define BK1(x)	cast(lua_Unsigned, ((x) << 8) | LUA_VEMPTY)
-
 /*
-** Clear new slice of the array, in bulk.
+** Clear new slice of the array.
 */
 static void clearNewSlice (Table *t, unsigned oldasize, unsigned newasize) {
-  int i, j;
-  int firstcell = (oldasize + NM - 1) / NM;
-  int lastcell = cast_int((newasize + NM - 1) / NM) - 1;
-  for (i = firstcell; i <= lastcell; i++) {
-    /* empty tag repeated for all tags in a word */
-    const lua_Unsigned empty = BK1(BK1(BK1(BK1(BK1(BK1(BK1(BK1(0))))))));
-    for (j = 0; j < BKSZ; j++)
-      t->array[i].u.bulk[j] = empty;
-  }
+  for (; oldasize < newasize; oldasize++)
+    *getArrTag(t, oldasize) = LUA_VEMPTY;
 }
 
 
diff --git a/ltable.h b/ltable.h
@@ -87,32 +87,20 @@
 
 
 /*
-** The array part of a table is represented by an array of *cells*.
+** The array part of a table is represented by an array of cells.
 ** Each cell is composed of NM tags followed by NM values, so that
 ** no space is wasted in padding.
 */
 #define NM      cast_uint(sizeof(Value))
 
-
-/*
-** A few operations on arrays can be performed "in bulk", treating all
-** tags of a cell as a simple (or a few) word(s). The next constant is
-** the number of words to cover the tags of a cell. (In conventional
-** architectures that will be 1 or 2.)
-*/
-#define BKSZ	cast_int((NM - 1) / sizeof(lua_Unsigned) + 1)
-
 struct ArrayCell {
-  union {
-    lua_Unsigned bulk[BKSZ];  /* for "bulk" operations */
-    lu_byte tag[NM];
-  } u;
+  lu_byte tag[NM];
   Value value[NM];
 };
 
 
 /* Computes the address of the tag for the abstract index 'k' */
-#define getArrTag(t,k)	(&(t)->array[(k)/NM].u.tag[(k)%NM])
+#define getArrTag(t,k)	(&(t)->array[(k)/NM].tag[(k)%NM])
 
 /* Computes the address of the value for the abstract index 'k' */
 #define getArrVal(t,k)	(&(t)->array[(k)/NM].value[(k)%NM])