From 7ea5aeedfd0a864d47331194f3a101deaa34b4be Mon Sep 17 00:00:00 2001
From: Araq <araq4k@proton.me>
Date: Sat, 13 Jun 2026 21:03:55 +0200
Subject: [PATCH] IC: add inert --icBackendStage/--icBackendModule switches
 (Phase 2b scaffold)

Config plumbing for the per-module backend: icBackendStage (cg|merge|emit, empty
= today's whole-program backend) and icBackendModule (the NIF suffix the cg/emit
stage operates on). No behavior yet -- the nifbackend stages and deps.nim rules
that consume these land next. Whole-program backend, koch boot, and a 2-module
IC build are unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 compiler/commands.nim | 13 +++++++++++++
 compiler/options.nim  | 12 ++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/compiler/commands.nim b/compiler/commands.nim
index 3a8ae18559..f5434fb621 100644
--- a/compiler/commands.nim
+++ b/compiler/commands.nim
@@ -960,6 +960,19 @@ proc processSwitch*(switch, arg: string, pass: TCmdLinePass, info: TLineInfo;
     # config loading can replay it instead of re-parsing the `nim.cfg` chain.
     expectArg(conf, switch, arg, pass, info)
     conf.icPreparsedConfig = arg
+  of "icbackendstage":
+    # `nim nifc` only: per-module backend stage, one of cg|merge|emit (see
+    # options.icBackendStage). Empty (switch unused) keeps the whole-program
+    # backend. Emitted by `deps.nim`'s backend build file.
+    expectArg(conf, switch, arg, pass, info)
+    if pass in {passCmd2, passPP}:
+      conf.icBackendStage = arg
+  of "icbackendmodule":
+    # `nim nifc` only: the NIF module suffix the cg/emit stage operates on (see
+    # options.icBackendModule).
+    expectArg(conf, switch, arg, pass, info)
+    if pass in {passCmd2, passPP}:
+      conf.icBackendModule = arg
   of "import":
     expectArg(conf, switch, arg, pass, info)
     if pass in {passCmd2, passPP}:
diff --git a/compiler/options.nim b/compiler/options.nim
index 1c78a77181..fd194e0b23 100644
--- a/compiler/options.nim
+++ b/compiler/options.nim
@@ -418,6 +418,18 @@ type
                               # process; only the `ic` driver serialises them.
                               # Path-search switches are excluded — the driver
                               # forwards the resolved `searchPaths` as `--path`.
+    icBackendStage*: string   # under `nim nifc`: which stage of the per-module
+                              # backend this invocation runs — "cg" (codegen one
+                              # module to its `.c.nif`), "merge" (global liveness
+                              # + owner assignment across all `.c.nif`), "emit"
+                              # (render one module's `.c` from its `.c.nif` + the
+                              # merge decision). Empty = today's whole-program
+                              # backend (load all, codegen+DCE+cc+link in one
+                              # process). See `compiler/nifbackend.nim`.
+    icBackendModule*: string  # under `nim nifc` with icBackendStage in {cg,emit}:
+                              # the NIF module suffix this invocation codegens or
+                              # emits. The other modules are loaded only so types
+                              # resolve; their definitions are referenced extern.
     spellSuggestMax*: int # max number of spelling suggestions for typos
 
     cppDefines*: HashSet[string] # (*)