In the sqlite3_context object, keep a pointer to the result value rather

than storing the result value in the sqlite3_context object and using
memcpy() to move the value back into its register
after the function returns.  This runs faster and saves over 500 bytes
of code space.

FossilOrigin-Name: 6c1ee3e388eb110de815270467b1e50592c0ba6c

src/vdbe.c

@@ -1545,8 +1545,8 @@ case OP_Function: {
   apVal = p->apArg;
   assert( apVal || n==0 );
   assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
-  pOut = &aMem[pOp->p3];
-  memAboutToChange(p, pOut);
+  ctx.pOut = &aMem[pOp->p3];
+  memAboutToChange(p, ctx.pOut);
 
   assert( n==0 || (pOp->p2>0 && pOp->p2+n<=(p->nMem-p->nCursor)+1) );
   assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
@@ -1562,16 +1562,7 @@ case OP_Function: {
   ctx.pFunc = pOp->p4.pFunc;
   ctx.iOp = pc;
   ctx.pVdbe = p;
-
-  /* The output cell may already have a buffer allocated. Move
-  ** the pointer to ctx.s so in case the user-function can use
-  ** the already allocated buffer instead of allocating a new one.
-  */
-  memcpy(&ctx.s, pOut, sizeof(Mem));
-  pOut->flags = MEM_Null;
-  pOut->xDel = 0;
-  pOut->zMalloc = 0;
-  MemSetTypeFlag(&ctx.s, MEM_Null);
+  MemSetTypeFlag(ctx.pOut, MEM_Null);
 
   ctx.fErrorOrAux = 0;
   if( ctx.pFunc->funcFlags & SQLITE_FUNC_NEEDCOLL ){
@@ -1584,43 +1575,23 @@ case OP_Function: {
   (*ctx.pFunc->xFunc)(&ctx, n, apVal); /* IMP: R-24505-23230 */
   lastRowid = db->lastRowid;
 
-  if( db->mallocFailed ){
-    /* Even though a malloc() has failed, the implementation of the
-    ** user function may have called an sqlite3_result_XXX() function
-    ** to return a value. The following call releases any resources
-    ** associated with such a value.
-    */
-    sqlite3VdbeMemRelease(&ctx.s);
-    goto no_mem;
-  }
-
   /* If the function returned an error, throw an exception */
   if( ctx.fErrorOrAux ){
     if( ctx.isError ){
-      sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(&ctx.s));
+      sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(ctx.pOut));
       rc = ctx.isError;
     }
     sqlite3VdbeDeleteAuxData(p, pc, pOp->p1);
   }
 
   /* Copy the result of the function into register P3 */
-  sqlite3VdbeChangeEncoding(&ctx.s, encoding);
-  assert( pOut->flags==MEM_Null );
-  memcpy(pOut, &ctx.s, sizeof(Mem));
-  if( sqlite3VdbeMemTooBig(pOut) ){
+  sqlite3VdbeChangeEncoding(ctx.pOut, encoding);
+  if( sqlite3VdbeMemTooBig(ctx.pOut) ){
     goto too_big;
   }
 
-#if 0
-  /* The app-defined function has done something that as caused this
-  ** statement to expire.  (Perhaps the function called sqlite3_exec()
-  ** with a CREATE TABLE statement.)
-  */
-  if( p->expired ) rc = SQLITE_ABORT;
-#endif
-
-  REGISTER_TRACE(pOp->p3, pOut);
-  UPDATE_MAX_BLOBSIZE(pOut);
+  REGISTER_TRACE(pOp->p3, ctx.pOut);
+  UPDATE_MAX_BLOBSIZE(ctx.pOut);
   break;
 }
 
@@ -5610,6 +5581,7 @@ case OP_AggStep: {
   int i;
   Mem *pMem;
   Mem *pRec;
+  Mem t;
   sqlite3_context ctx;
   sqlite3_value **apVal;
 
@@ -5627,11 +5599,12 @@ case OP_AggStep: {
   assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
   ctx.pMem = pMem = &aMem[pOp->p3];
   pMem->n++;
-  ctx.s.flags = MEM_Null;
-  ctx.s.z = 0;
-  ctx.s.zMalloc = 0;
-  ctx.s.xDel = 0;
-  ctx.s.db = db;
+  t.flags = MEM_Null;
+  t.z = 0;
+  t.zMalloc = 0;
+  t.xDel = 0;
+  t.db = db;
+  ctx.pOut = &t;
   ctx.isError = 0;
   ctx.pColl = 0;
   ctx.skipFlag = 0;
@@ -5643,7 +5616,7 @@ case OP_AggStep: {
   }
   (ctx.pFunc->xStep)(&ctx, n, apVal); /* IMP: R-24505-23230 */
   if( ctx.isError ){
-    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(&ctx.s));
+    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(&t));
     rc = ctx.isError;
   }
   if( ctx.skipFlag ){
@@ -5651,9 +5624,7 @@ case OP_AggStep: {
     i = pOp[-1].p1;
     if( i ) sqlite3VdbeMemSetInt64(&aMem[i], 1);
   }
-
-  sqlite3VdbeMemRelease(&ctx.s);
-
+  sqlite3VdbeMemRelease(&t);
   break;
 }
 
@@ -6103,27 +6074,14 @@ case OP_VColumn: {
   pModule = pVtab->pModule;
   assert( pModule->xColumn );
   memset(&sContext, 0, sizeof(sContext));
-
-  /* The output cell may already have a buffer allocated. Move
-  ** the current contents to sContext.s so in case the user-function 
-  ** can use the already allocated buffer instead of allocating a 
-  ** new one.
-  */
-  sqlite3VdbeMemMove(&sContext.s, pDest);
-  MemSetTypeFlag(&sContext.s, MEM_Null);
-
+  sContext.pOut = pDest;
+  MemSetTypeFlag(pDest, MEM_Null);
   rc = pModule->xColumn(pCur->pVtabCursor, &sContext, pOp->p2);
   sqlite3VtabImportErrmsg(p, pVtab);
   if( sContext.isError ){
     rc = sContext.isError;
   }
-
-  /* Copy the result of the function to the P3 register. We
-  ** do this regardless of whether or not an error occurred to ensure any
-  ** dynamic allocation in sContext.s (a Mem struct) is  released.
-  */
-  sqlite3VdbeChangeEncoding(&sContext.s, encoding);
-  sqlite3VdbeMemMove(pDest, &sContext.s);
+  sqlite3VdbeChangeEncoding(pDest, encoding);
   REGISTER_TRACE(pOp->p3, pDest);
   UPDATE_MAX_BLOBSIZE(pDest);