'lineinfo' in prototypes saved as differences instead of absolute

values, so that the array can use bytes instead of ints, reducing
its size. (A new array 'abslineinfo' is used when line differences
do not fit in a byte.)

1 files changed, 45 insertions, 7 deletions

diff --git a/lcode.c b/lcode.c
index 2d396000..740cf564 100644
--- a/lcode.c
+++ b/lcode.c
@@ -1,5 +1,5 @@
 /*
-** $Id: lcode.c,v 2.118 2017/04/28 20:57:45 roberto Exp roberto $
+** $Id: lcode.c,v 2.119 2017/05/18 19:44:19 roberto Exp roberto $
 ** Code generator for Lua
 ** See Copyright Notice in lua.h
 */
@@ -10,6 +10,7 @@
 #include "lprefix.h"
 
 
+#include <limits.h>
 #include <math.h>
 #include <stdlib.h>
 
@@ -285,6 +286,33 @@ void luaK_patchclose (FuncState *fs, int list, int level) {
   }
 }
 
+#if !defined(MAXIWTHABS)
+#define MAXIWTHABS      120
+#endif
+
+/*
+** Save line info for a new instruction. If difference from last line
+** does not fit in a byte, of after that many instructions, save a new
+** absolute line info; (in that case, the special value 'ABSLINEINFO'
+** in 'lineinfo' signals the existence of this absolute information.)
+** Otherwise, store the difference from last line in 'lineinfo'.
+*/
+static void savelineinfo (FuncState *fs, Proto *f, int pc, int line) {
+  int linedif = line - fs->previousline;
+  if (abs(linedif) >= 0x80 || fs->iwthabs++ > MAXIWTHABS) {
+    luaM_growvector(fs->ls->L, f->abslineinfo, fs->nabslineinfo,
+                    f->sizeabslineinfo, AbsLineInfo, MAX_INT, "lines");
+    f->abslineinfo[fs->nabslineinfo].pc = pc;
+    f->abslineinfo[fs->nabslineinfo++].line = line;
+    linedif = ABSLINEINFO;  /* signal there is absolute information */
+    fs->iwthabs = 0;  /* restart counter */
+  }
+  luaM_growvector(fs->ls->L, f->lineinfo, pc, f->sizelineinfo, ls_byte,
+                  MAX_INT, "opcodes");
+  f->lineinfo[pc] = linedif;
+  fs->previousline = line;  /* last line saved */
+}
+
 
 /*
 ** Emit instruction 'i', checking for array sizes and saving also its
@@ -297,10 +325,7 @@ static int luaK_code (FuncState *fs, Instruction i) {
   luaM_growvector(fs->ls->L, f->code, fs->pc, f->sizecode, Instruction,
                   MAX_INT, "opcodes");
   f->code[fs->pc] = i;
-  /* save corresponding line information */
-  luaM_growvector(fs->ls->L, f->lineinfo, fs->pc, f->sizelineinfo, int,
-                  MAX_INT, "opcodes");
-  f->lineinfo[fs->pc] = fs->ls->lastline;
+  savelineinfo(fs, f, fs->pc, fs->ls->lastline);
   return fs->pc++;
 }
 
@@ -1260,10 +1285,23 @@ void luaK_posfix (FuncState *fs, BinOpr op,
 
 
 /*
-** Change line information associated with current position.
+** Change line information associated with current position. If that
+** information is absolute, just change it and correct 'previousline'.
+** Otherwise, restore 'previousline' to its value before saving the
+** current position and than saves the line information again, with the
+** new line.
 */
 void luaK_fixline (FuncState *fs, int line) {
-  fs->f->lineinfo[fs->pc - 1] = line;
+  Proto *f = fs->f;
+  if (f->lineinfo[fs->pc - 1] == ABSLINEINFO) {
+    lua_assert(f->abslineinfo[fs->nabslineinfo - 1].pc == fs->pc - 1);
+    f->abslineinfo[fs->nabslineinfo - 1].line = line;
+    fs->previousline = line;
+  }
+  else {
+    fs->previousline -= f->lineinfo[fs->pc - 1];  /* undo previous info. */
+    savelineinfo(fs, f, fs->pc - 1, line);  /* redo it */ 
+  }
 }