Optimize stringlist functions

The get_string() function becomes a major bottleneck (around 80% of
the time) when debug info is on because it uses a linked list for
storage and it's mostly called in for loops iterating over the whole
list by index. That's a quadratic complexity.

This patch rewrites all stringlist functions to use an array instead
of a linked list. It decreased my test script's compile time from 84s
to 10s, or by 730%(!). The script is just 100,000 lines of print()
statements. If debug info is turned off the times are the same for both
implementations.

source/compiler/sc.h

@@ -264,8 +264,8 @@ enum {
 };
 
 typedef struct s_stringlist {
-  struct s_stringlist *next;
+  char **strings;
-  char *line;
+  int size;
 } stringlist;
 
 typedef struct s_stringpair {

source/compiler/sclist.c

@@ -135,71 +135,69 @@ static int delete_stringpair(stringpair *root,stringpair *item)
 }
 
 /* ----- string list functions ----------------------------------- */
-static stringlist *insert_string(stringlist *root,char *string)
+static stringlist *insert_string(stringlist *list,char *string)
 {
-  stringlist *cur;
+  char **newstrings;
+  int newsize;
+  int i;
 
   assert(string!=NULL);
-  if ((cur=(stringlist*)malloc(sizeof(stringlist)))==NULL)
+  if (list->strings==NULL) {
+    /* list is used for the first time */
+    newsize=10;
+    if ((newstrings=calloc(newsize,sizeof(char*)))==NULL)
       error(103);       /* insufficient memory (fatal error) */
-  if ((cur->line=duplicatestring(string))==NULL)
+    list->strings=newstrings;
+    list->size=newsize;
+  } /* if */
+  for (i=0; i<list->size; i++)
+    if (list->strings[i]==NULL)
+      break;
+  if (i==list->size) {
+    /* double the size of the list */
+    newsize=list->size*2;
+    if ((newstrings=realloc(list->strings,newsize*sizeof(char*)))==NULL)
+      error(103);       /* insufficient memory (fatal error) */
+    memset(newstrings+list->size,0,list->size*sizeof(char*));
+    list->strings=newstrings;
+    list->size=newsize;
+  } /* if */
+  if ((list->strings[i]=duplicatestring(string))==NULL)
     error(103);         /* insufficient memory (fatal error) */
   /* insert as "last" */
-  assert(root!=NULL);
+  return list;
-  while (root->next!=NULL)
-    root=root->next;
-  cur->next=root->next;
-  root->next=cur;
-  return cur;
 }
 
-static char *get_string(stringlist *root,int index)
+static char *get_string(stringlist *list,int index)
 {
-  stringlist *cur;
+  assert(list!=NULL);
-
+  if (index>=0 && index<list->size)
-  assert(root!=NULL);
+    return list->strings[index];
-  cur=root->next;
-  while (cur!=NULL && index-->0)
-    cur=cur->next;
-  if (cur!=NULL) {
-    assert(cur->line!=NULL);
-    return cur->line;
-  } /* if */
   return NULL;
 }
 
-static int delete_string(stringlist *root,int index)
+static int delete_string(stringlist *list,int index)
 {
-  stringlist *cur,*item;
+  assert(list!=NULL);
-
+  if (index>=0 && index<list->size) {
-  assert(root!=NULL);
+    if (list->strings[index]!=NULL) {
-  for (cur=root; cur->next!=NULL && index>0; cur=cur->next,index--)
+      free(list->strings[index]);
-    /* nothing */;
+      list->strings[index]=NULL;
-  if (cur->next!=NULL) {
-    item=cur->next;
-    cur->next=item->next;       /* unlink from list */
-    assert(item->line!=NULL);
-    free(item->line);
-    free(item);
       return TRUE;
     } /* if */
+  } /* if */
   return FALSE;
 }
 
-SC_FUNC void delete_stringtable(stringlist *root)
+SC_FUNC void delete_stringtable(stringlist *list)
 {
-  stringlist *cur,*next;
+  int i;
   
-  assert(root!=NULL);
+  assert(list!=NULL);
-  cur=root->next;
+  for (i=0; i<list->size; i++)
-  while (cur!=NULL) {
+    free(list->strings[i]);
-    next=cur->next;
+  free(list->strings);
-    assert(cur->line!=NULL);
+  memset(list,0,sizeof(stringlist));
-    free(cur->line);
-    free(cur);
-    cur=next;
-  } /* while */
-  memset(root,0,sizeof(stringlist));
 }
 
 
@@ -235,7 +233,7 @@ SC_FUNC void delete_aliastable(void)
 }
 
 /* ----- include paths list -------------------------------------- */
-static stringlist includepaths = {NULL, NULL};  /* directory list for include files */
+static stringlist includepaths = {NULL, 0};  /* directory list for include files */
 
 SC_FUNC stringlist *insert_path(char *path)
 {
@@ -250,7 +248,7 @@ SC_FUNC char *get_path(int index)
 SC_FUNC void delete_pathtable(void)
 {
   delete_stringtable(&includepaths);
-  assert(includepaths.next==NULL);
+  assert(includepaths.strings==NULL);
 }
 
 
@@ -323,7 +321,7 @@ SC_FUNC void delete_substtable(void)
 
 
 /* ----- input file list ----------------------------------------- */
-static stringlist sourcefiles = {NULL, NULL};
+static stringlist sourcefiles = {NULL, 0};
 
 SC_FUNC stringlist *insert_sourcefile(char *string)
 {
@@ -338,13 +336,13 @@ SC_FUNC char *get_sourcefile(int index)
 SC_FUNC void delete_sourcefiletable(void)
 {
   delete_stringtable(&sourcefiles);
-  assert(sourcefiles.next==NULL);
+  assert(sourcefiles.strings==NULL);
 }
 
 
 /* ----- documentation tags -------------------------------------- */
 #if !defined SC_LIGHT
-static stringlist docstrings = {NULL, NULL};
+static stringlist docstrings = {NULL, 0};
 
 SC_FUNC stringlist *insert_docstring(char *string)
 {
@@ -364,13 +362,13 @@ SC_FUNC void delete_docstring(int index)
 SC_FUNC void delete_docstringtable(void)
 {
   delete_stringtable(&docstrings);
-  assert(docstrings.next==NULL);
+  assert(docstrings.strings==NULL);
 }
 #endif /* !defined SC_LIGHT */
 
 
 /* ----- autolisting --------------------------------------------- */
-static stringlist autolist = {NULL, NULL};
+static stringlist autolist = {NULL, 0};
 
 SC_FUNC stringlist *insert_autolist(char *string)
 {
@@ -385,7 +383,7 @@ SC_FUNC char *get_autolist(int index)
 SC_FUNC void delete_autolisttable(void)
 {
   delete_stringtable(&autolist);
-  assert(autolist.next==NULL);
+  assert(autolist.strings==NULL);
 }
 
 
@@ -462,7 +460,7 @@ SC_FUNC void delete_heaplisttable(void)
   #define PRIxC  "x"
 #endif
 
-static stringlist dbgstrings = {NULL, NULL};
+static stringlist dbgstrings = {NULL, 0};
 
 SC_FUNC stringlist *insert_dbgfile(const char *filename)
 {
@@ -530,5 +528,5 @@ SC_FUNC char *get_dbgstring(int index)
 SC_FUNC void delete_dbgstringtable(void)
 {
   delete_stringtable(&dbgstrings);
-  assert(dbgstrings.next==NULL);
+  assert(dbgstrings.strings==NULL);
 }