lua LCD (Lua Compact Debug) patch

LCD developed 9/2015 by Terry Ellison

 We've already discarded the ldebug module from lua
 it only makes sense to discard the debug info as well
 adds 1.5 K to the binary
 saves 8 Kb on the base state
 once scripts start getting called i've seen 10-50Kb savings but it all depends on
 what exactly you are running

Change-Id: Ibb74f344df1c4c96380ec6c98b010a810e9ae9cc

apps/plugins/lua/lcode.c

@@ -784,8 +784,95 @@ void luaK_posfix (FuncState *fs, BinOpr op, expdesc *e1, expdesc *e2) {
 }
 
 
+#ifdef LUA_OPTIMIZE_DEBUG
+/*
+ * Attempted to write to last (null terminator) byte of lineinfo, so need
+ * to grow the lineinfo vector and extend the fill bytes
+ */
+static unsigned char *growLineInfo(FuncState *fs) {
+  Proto *f = fs->f;
+  int start = (f->sizelineinfo > 0 ? f->sizelineinfo - 1 : 0);
+
+  unsigned char *p;
+
+  lua_assert(f->packedlineinfo==NULL || f->packedlineinfo[start] == '\0');
+
+  /* using the macro results in a redundant if test, but what the hell */
+  luaM_growvector(fs->L, f->packedlineinfo, f->sizelineinfo, f->sizelineinfo,
+                  unsigned char, MAX_INT, "code size overflow");
+
+  p = &f->packedlineinfo[start];
+  memset(p, INFO_FILL_BYTE, f->sizelineinfo - start);
+  f->packedlineinfo[f->sizelineinfo - 1] = '\0';
+  return p;
+}
+
+
+static void generateInfoDeltaLine(FuncState *fs, int line) {
+  /* Handle first time through when lineinfo points is NULL */
+  unsigned char mask = INFO_DELTA_MASK;
+  unsigned char *p = fs->f->packedlineinfo ? lineInfoTop(fs) + 1 : growLineInfo(fs);
+#define addDLbyte(v) if (*p=='\0') p = growLineInfo(fs); *p++ = (v);
+  int delta = line - fs->lastline - 1;
+  if (delta != 0) {
+    if (delta < 0) {
+      delta = -delta;
+      mask |= INFO_SIGN_MASK;
+    }
+    delta -= 1;
+    mask |= (delta & INFO_DELTA_6BITS);
+    delta >>= 6;
+    addDLbyte(mask);
+
+    while (delta > 0) {
+      mask = INFO_DELTA_MASK | (delta & INFO_DELTA_7BITS);
+      delta >>= 7;
+      addDLbyte(mask);
+    }
+  }
+  addDLbyte(1);
+  fs->lastline = line;
+  fs->lastlineOffset = p - fs->f->packedlineinfo - 1;
+#undef addDLbyte
+}
+#endif
+
+
 void luaK_fixline (FuncState *fs, int line) {
+#ifdef LUA_OPTIMIZE_DEBUG
+  /* The fixup line can be the same as existing one and in this case there's nothing to do */
+  if (line != fs->lastline) {
+    /* first remove the current line reference */
+    unsigned char *p = lineInfoTop(fs);
+    lua_assert(*p < 127);
+    if (*p >1) {
+      (*p)--;    /* this is simply decrementing the last count a multi-PC line */
+    } else {
+      /* it's a bit more complicated if it's the 1st instruction on the line */
+      int delta = 0;
+      unsigned char code;
+      /* this logic handles <i/c> [1snnnnnnn [1nnnnnnn]*]? <i/c=1> */
+      *p-- = INFO_FILL_BYTE;
+      /* work backwards over the coded delta computing the delta */
+      while ((code=*p) & INFO_DELTA_MASK) {
+        *p-- = INFO_FILL_BYTE;
+        if (*p & INFO_DELTA_MASK) {
+          delta += ((code & INFO_DELTA_7BITS)<<7);
+        } else {
+          delta += (code & INFO_DELTA_6BITS) + 1;
+          if (code & INFO_SIGN_MASK) delta = -delta;
+        }
+      }
+      /* and reposition the FuncState lastline pointers at the previous instruction count */
+      fs->lastline-= delta + 1;
+      fs->lastlineOffset = p - fs->f->packedlineinfo;
+    }
+    /* Then add the new line reference */
+    generateInfoDeltaLine(fs, line);
+  }
+#else
   fs->f->lineinfo[fs->pc - 1] = line;
+#endif
 }
 
 
@@ -797,9 +884,25 @@ static int luaK_code (FuncState *fs, Instruction i, int line) {
                   MAX_INT, "code size overflow");
   f->code[fs->pc] = i;
   /* save corresponding line information */
+#ifdef LUA_OPTIMIZE_DEBUG
+  /* note that frst time fs->lastline==0 through, so the else branch is taken */
+  if (fs->pc == fs->lineinfoLastPC+1) {
+    if (line == fs->lastline && f->packedlineinfo[fs->lastlineOffset] < INFO_MAX_LINECNT) {
+      f->packedlineinfo[fs->lastlineOffset]++;
+    } else {
+      generateInfoDeltaLine(fs, line);
+    }
+  } else {
+    /* The last instruction is occasionally overwritten as part of branch optimisation*/
+    lua_assert(fs->pc == fs->lineinfoLastPC);  /* panic if its anything other than this !! */
+    luaK_fixline(fs,line);
+  }
+  fs->lineinfoLastPC = fs->pc;
+#else
   luaM_growvector(fs->L, f->lineinfo, fs->pc, f->sizelineinfo, int,
                   MAX_INT, "code size overflow");
   f->lineinfo[fs->pc] = line;
+#endif
   return fs->pc++;
 }