adds an option to interleave the generated code with snippets from the original source

Lines from the original source are outputted as comments next to line directives.
Hopefully, this will make debugging codegen problems easier.

Other changes:
The frame setup code now uses a single-line C macro. My motivation was to reduce
the noise in the generated output and make it easier to step over the boiler-plate
code, but counter-intuitively this also improved the overall compilation speed a
little bit so I applied the same treatment to line tracking too (this reduces the size of
the generated files and the explanation is that probably the I/O overhead dominates
the macro expansion costs).

compiler/cgen.nim

@@ -271,15 +271,18 @@ proc genCLineDir(r: var PRope, info: TLineInfo) =
 
 proc genLineDir(p: BProc, t: PNode) = 
   var line = t.info.safeLineNm
+  if optEmbedOrigSrc in gGlobalOptions:
+    app(p.s(cpsStmts), con(~"//", t.info.sourceLine, rnl))
   genCLineDir(p.s(cpsStmts), t.info.toFullPath, line)
   if ({optStackTrace, optEndb} * p.Options == {optStackTrace, optEndb}) and
       (p.prc == nil or sfPure notin p.prc.flags): 
     linefmt(p, cpsStmts, "#endb($1);$n", toRope(line))
   elif ({optLineTrace, optStackTrace} * p.Options ==
       {optLineTrace, optStackTrace}) and
-      (p.prc == nil or sfPure notin p.prc.flags): 
-    lineF(p, cpsStmts, "F.line = $1;F.filename = $2;$n", 
-        [toRope(line), makeCString(toFilename(t.info).extractFilename)])
+      (p.prc == nil or sfPure notin p.prc.flags):
+   
+    linefmt(p, cpsStmts, "nimln($1, $2);$n",
+            line.toRope, t.info.quotedFilename)
 
 include "ccgtypes.nim"
 
@@ -696,33 +699,17 @@ proc generateHeaders(m: BModule) =
       appf(m.s[cfsHeaders], "$N#include $1$N", [toRope(it.data)])
     it = PStrEntry(it.Next)
 
-proc getFrameDecl(p: BProc) = 
-  var slots: PRope
-  if p.frameLen > 0: 
-    discard cgsym(p.module, "TVarSlot")
-    slots = ropeff("  TVarSlot s[$1];$n", ", [$1 x %TVarSlot]", 
-                   [toRope(p.frameLen)])
-  else: 
-    slots = nil
-  lineFF(p, cpsLocals, "volatile struct {TFrame* prev;" &
-      "NCSTRING procname;NI line;NCSTRING filename;" &
-      "NI len;$1} F;$n",
-      "%TF = type {%TFrame*, i8*, %NI, %NI$1}$n" & 
-      "%F = alloca %TF$n", [slots])
-  inc(p.labels)
-  prepend(p.s(cpsInit), indentLine(p, ropeff("F.len = $1;$n", 
-      "%LOC$2 = getelementptr %TF %F, %NI 4$n" &
-      "store %NI $1, %NI* %LOC$2$n", [toRope(p.frameLen), toRope(p.labels)])))
-
 proc retIsNotVoid(s: PSym): bool = 
   result = (s.typ.sons[0] != nil) and not isInvalidReturnType(s.typ.sons[0])
 
-proc initFrame(p: BProc, procname, filename: PRope): PRope = 
-  result = ropecg(p.module, 
-    "\tF.procname = $1;$n" &
-    "\tF.filename = $2;$n" & 
-    "\tF.line = 0;$n" & 
-    "\t#pushFrame((TFrame*)&F);$n", [procname, filename])
+proc initFrame(p: BProc, procname, filename: PRope): PRope =
+  discard cgsym(p.module, "pushFrame")
+  if p.frameLen > 0:
+    discard cgsym(p.module, "TVarSlot")
+    result = rfmt(nil, "\tnimfrs($1, $2, $3)$N",
+                  procname, filename, p.frameLen.toRope)
+  else:
+    result = rfmt(nil, "\tnimfr($1, $2)$N", procname, filename)
 
 proc deinitFrame(p: BProc): PRope =
   result = rfmt(p.module, "\t#popFrame();$n")
@@ -774,11 +761,9 @@ proc genProcAux(m: BModule, prc: PSym) =
     generatedProc = rfmt(nil, "$N$1 {$N", header)
     app(generatedProc, initGCFrame(p))
     if optStackTrace in prc.options: 
-      getFrameDecl(p)
       app(generatedProc, p.s(cpsLocals))
       var procname = CStringLit(p, generatedProc, prc.name.s)
-      var filename = CStringLit(p, generatedProc, toFilename(prc.info))
-      app(generatedProc, initFrame(p, procname, filename))
+      app(generatedProc, initFrame(p, procname, prc.info.quotedFilename))
     else: 
       app(generatedProc, p.s(cpsLocals))
     if (optProfiler in prc.options) and (gCmd != cmdCompileToLLVM):
@@ -1014,11 +999,6 @@ proc genInitCode(m: BModule) =
   if m.nimTypes > 0: 
     appcg(m, m.s[cfsTypeInit1], "static #TNimType $1[$2];$n", 
           [m.nimTypesName, toRope(m.nimTypes)])
-  if optStackTrace in m.initProc.options and not m.FrameDeclared:
-    # BUT: the generated init code might depend on a current frame, so
-    # declare it nevertheless:
-    m.FrameDeclared = true
-    getFrameDecl(m.initProc)
   
   app(prc, initGCFrame(m.initProc))
  
@@ -1027,11 +1007,16 @@ proc genInitCode(m: BModule) =
   app(prc, m.preInitProc.s(cpsLocals))
   app(prc, genSectionEnd(cpsLocals))
 
-  if optStackTrace in m.initProc.options and not m.PreventStackTrace: 
-    var procname = CStringLit(m.initProc, prc, m.module.name.s)
-    var filename = CStringLit(m.initProc, prc, toFilename(m.module.info))
-    app(prc, initFrame(m.initProc, procname, filename))
- 
+  if optStackTrace in m.initProc.options and not m.FrameDeclared:
+    # BUT: the generated init code might depend on a current frame, so
+    # declare it nevertheless:
+    m.FrameDeclared = true
+    if not m.PreventStackTrace:
+      var procname = CStringLit(m.initProc, prc, m.module.name.s)
+      app(prc, initFrame(m.initProc, procname, m.module.info.quotedFilename))
+    else:
+      app(prc, ~"\tvolatile TFrame F; F.len = 0;$N")
+    
   app(prc, genSectionStart(cpsInit))
   app(prc, m.preInitProc.s(cpsInit))
   app(prc, m.initProc.s(cpsInit))