Regression from 2.0 to `version-2-2`/`devel` with `refc`, LTO and `-fstack-usage`

[tersec]

Nim Version

Nim Compiler Version 2.0.15 [Linux: amd64]
Compiled at 2025-03-04
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: 41637db18f6a82df4a92f2e00a780e5815d17028
active boot switches: -d:release

Nim Compiler Version 2.2.3 [Linux: amd64]
Compiled at 2025-03-04
Copyright (c) 2006-2025 by Andreas Rumpf

git hash: 58f1e22db352ed3cff0f9303acf064a291c25d8d
active boot switches: -d:release

Nim Compiler Version 2.3.1 [Linux: amd64]
Compiled at 2025-03-04
Copyright (c) 2006-2025 by Andreas Rumpf

git hash: e39d152b89c5635c27dd4d8fc71c48747c5fc20b
active boot switches: -d:release

gcc (Debian 14.2.0-17) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Description

proc h(): array[524288, byte] =
  # Other conditional-adjacent expressions (case, try, etc) also work here
  if true:
    result
  else:
    result

let v = h()   # to make Nim 2.0 fail too, use discard h()

Build with

nim c --passC="-flto -fstack-usage -Werror=stack-usage=262144" --passL="-flto -fstack-usage -Werror=stack-usage=262144" --mm:refc s.nim

Current Output

Hint: used config file '/tmp/nimdevel/config/nim.cfg' [Conf]
Hint: used config file '/tmp/nimdevel/config/config.nims' [Conf]
........................................................................
CC: nimdevel/lib/system/exceptions.nim
CC: nimdevel/lib/std/private/digitsutils.nim
CC: nimdevel/lib/system/dollars.nim
CC: nimdevel/lib/std/typedthreads.nim
CC: nimdevel/lib/pure/collections/sharedlist.nim
CC: nimdevel/lib/system.nim
CC: s.nim
Hint:  [Link]
/tmp/tmp.g0j3iBnZfH/@ms.nim.c: In function ‘h__s_u1’:
/tmp/tmp.g0j3iBnZfH/@ms.nim.c:91:15: error: stack usage is 1048656 bytes [-Werror=stack-usage=]
   91 | N_LIB_PRIVATE N_NIMCALL(void, h__s_u1)(tyArray__msnM9cX4aNc7VxW6WzOqyjA Result) {
      |               ^
lto1: some warnings being treated as errors
lto-wrapper: fatal error: gcc returned 1 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
Error: execution of an external program failed: 'gcc   -o /tmp/s  /tmp/tmp.g0j3iBnZfH/@mnimdevel@slib@[email protected] /tmp/tmp.g0j3iBnZfH/@mnimdevel@slib@sstd@[email protected] /tmp/tmp.g0j3iBnZfH/@mnimdevel@slib@[email protected] /tmp/tmp.g0j3iBnZfH/@mnimdevel@slib@[email protected] /tmp/tmp.g0j3iBnZfH/@mnimdevel@slib@spure@[email protected] /tmp/tmp.g0j3iBnZfH/@mnimdevel@[email protected] /tmp/tmp.g0j3iBnZfH/@ms.nim.c.o  -pthread -pthread  -flto -fstack-usage -Werror=stack-usage=262144  -ldl'

Expected Output

Known Workarounds

No response

Additional Information

No response

[tersec]

A diff of the C source generated -- some variable name noise, but fairly clear superficially what changed:

@@ -90,41 +75,49 @@
 }
 static N_INLINE(void, nimFrame)(TFrame *s_p0) {
   {
-    if (!(framePtr__system_u2617 == ((TFrame *)NIM_NIL)))
+    if (!(framePtr__system_u2710 == ((TFrame *)NIM_NIL)))
       goto LA3_;
     (*s_p0).calldepth = ((NI16)0);
   }
   goto LA1_;
 LA3_:;
   {
-    (*s_p0).calldepth = (NI16)((*framePtr__system_u2617).calldepth + ((NI16)1));
+    (*s_p0).calldepth = (NI16)((*framePtr__system_u2710).calldepth + ((NI16)1));
   }
 LA1_:;
-  (*s_p0).prev = framePtr__system_u2617;
-  framePtr__system_u2617 = s_p0;
+  (*s_p0).prev = framePtr__system_u2710;
+  framePtr__system_u2710 = s_p0;
   {
     if (!((*s_p0).calldepth == ((NI16)2000)))
       goto LA8_;
-    callDepthLimitReached__system_u3150();
+    callDepthLimitReached__system_u3256();
   }
 LA8_:;
 }
 static N_INLINE(void, popFrame)(void) {
-  framePtr__system_u2617 = (*framePtr__system_u2617).prev;
+  framePtr__system_u2710 = (*framePtr__system_u2710).prev;
 }
 N_LIB_PRIVATE N_NIMCALL(void,
                         h__s_u1)(tyArray__msnM9cX4aNc7VxW6WzOqyjA Result) {
+  tyArray__msnM9cX4aNc7VxW6WzOqyjA colontmpD_;
+  tyArray__msnM9cX4aNc7VxW6WzOqyjA colontmpD__2;
   nimZeroMem((void *)Result, sizeof(tyArray__msnM9cX4aNc7VxW6WzOqyjA));
+  nimZeroMem((void *)colontmpD_, sizeof(tyArray__msnM9cX4aNc7VxW6WzOqyjA));
+  nimZeroMem((void *)colontmpD__2, sizeof(tyArray__msnM9cX4aNc7VxW6WzOqyjA));
   {
     if (!NIM_TRUE)
       goto LA3_;
-    nimCopyMem((void *)Result, (NIM_CONST void *)Result,
+    nimCopyMem((void *)colontmpD_, (NIM_CONST void *)Result,
+               sizeof(tyArray__msnM9cX4aNc7VxW6WzOqyjA));
+    nimCopyMem((void *)Result, (NIM_CONST void *)colontmpD_,
                sizeof(tyArray__msnM9cX4aNc7VxW6WzOqyjA));
   }
   goto LA1_;
 LA3_:;
   {
-    nimCopyMem((void *)Result, (NIM_CONST void *)Result,
+    nimCopyMem((void *)colontmpD__2, (NIM_CONST void *)Result,
+               sizeof(tyArray__msnM9cX4aNc7VxW6WzOqyjA));
+    nimCopyMem((void *)Result, (NIM_CONST void *)colontmpD__2,
                sizeof(tyArray__msnM9cX4aNc7VxW6WzOqyjA));
   }
 LA1_:;

[ringabout]

It breaks with ORC as well, related to https://github.com/nim-lang/Nim/issues/18341