When the tail-call pass converted a Call to TailCall inside an If branch,
and the inliner subsequently inlined that word, the TailCall was not
converted back to Call in nested control-flow bodies. The TailCall codegen
emits a Return instruction, which would exit the *caller* instead of just
the inlined callee — silently corrupting the return stack.
Root cause: the inliner only converted top-level TailCalls in the body
(line-by-line iteration), missing TailCalls nested inside If/DoLoop/Begin
structures.
Fix: add detailcall() that recursively walks the entire IR tree and
converts all TailCall ops back to Call before inlining.
This unblocks defining complex Forth words (like SM/REM, FM/MOD) that
use DABS → DNEGATE → D+ chains with return-stack operations inside
conditional branches.
426 tests pass (including new regression test).
ok2
0f6285ddfc