#
#
# The Nim Compiler
# (c) Copyright 2021 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## New entry point into our C/C++ code generator. Ideally
## somebody would rewrite the old backend (which is 8000 lines of crufty Nim code)
## to work on packed trees directly and produce the C code as an AST which can
## then be rendered to text in a very simple manner. Unfortunately nobody wrote
## this code. So instead we wrap the existing cgen.nim and its friends so that
## we call directly into the existing code generation logic but avoiding the
## naive, outdated `passes` design. Thus you will see some
## `useAliveDataFromDce in flags` checks in the old code -- the old code is
## also doing cross-module dependency tracking and DCE that we don't need
## anymore. DCE is now done as prepass over the entire packed module graph.
import std / [intsets, algorithm]
import ".." / [ast, options, lineinfos, modulegraphs, cgendata, cgen,
pathutils, extccomp, msgs]
import packed_ast, to_packed_ast, bitabs, dce, rodfiles
proc unpackTree(g: ModuleGraph; thisModule: int;
tree: PackedTree; n: NodePos): PNode =
var decoder = initPackedDecoder(g.config, g.cache)
result = loadNodes(decoder, g.packed, thisModule, tree, n)
proc generateCodeForModule(g: ModuleGraph; m: var LoadedModule; alive: var AliveSyms) =
if g.backend == nil:
g.backend = cgendata.newModuleList(g)
var bmod = cgen.newModule(BModuleList(g.backend), m.module, g.config)
bmod.idgen = idgenFromLoadedModule(m)
bmod.flags.incl useAliveDataFromDce
bmod.alive = move alive[m.module.position]
for p in allNodes(m.fromDisk.topLevel):
let n = unpackTree(g, m.module.position, m.fromDisk.topLevel, p)
cgen.genTopLevelStmt(bmod, n)
finalCodegenActions(g, bmod, newNodeI(nkStmtList, m.module.info))
proc addFileToLink(config: ConfigRef; m: PSym) =
let filename = AbsoluteFile toFullPath(config, m.position.FileIndex)
let ext =
if config.backend == backendCpp: ".nim.cpp"
elif config.backend == backendObjc: ".nim.m"
else: ".nim.c"
let cfile = changeFileExt(completeCfilePath(config, withPackageName(config, filename)), ext)
var cf = Cfile(nimname: m.name.s, cname: cfile,
obj: completeCfilePath(config, toObjFile(config, cfile)),
flags: {CfileFlag.Cached})
addFileToCompile(config, cf)
proc aliveSymsChanged(config: ConfigRef; position: int; alive: AliveSyms): bool =
let asymFile = toRodFile(config, AbsoluteFile toFullPath(config, position.FileIndex), ".alivesyms")
var s = newSeqOfCap[int32](alive[position].len)
for a in items(alive[position]): s.add int32(a)
sort(s)
var f2 = rodfiles.open(asymFile.string)
f2.loadHeader()
f2.loadSection aliveSymsSection
var oldData: seq[int32]
f2.loadSeq(oldData)
f2.close
if f2.err == ok and oldData == s:
result = false
else:
result = true
var f = rodfiles.create(asymFile.string)
f.storeHeader()
f.storeSection aliveSymsSection
f.storeSeq(s)
close f
proc generateCode*(g: ModuleGraph) =
## The single entry point, generate C(++) code for the entire
## Nim program aka `ModuleGraph`.
var alive = computeAliveSyms(g.packed, g.config)
for i in 0..high(g.packed):
# case statement here to enforce exhaustive checks.
case g.packed[i].status
of undefined:
discard "nothing to do"
of loading:
assert false
of storing, outdated:
generateCodeForModule(g, g.packed[i], alive)
of loaded:
# Even though this module didn't change, DCE might trigger a change.
# Consider this case: Module A uses symbol S from B and B does not use
# S itself. A is then edited not to use S either. Thus we have to
# recompile B in order to remove S from the final result.
if aliveSymsChanged(g.config, g.packed[i].module.position, alive):
generateCodeForModule(g, g.packed[i], alive)
else:
addFileToLink(g.config, g.packed[i].module)