; Pin: MachineCopyPropagation must NOT eliminate `COPY $img = $reg` —
; that COPY actually expands to STA_DP $D? (a DP-memory store to an
; IMG slot).  Libcalls (softDouble, softFloat) use those same DP
; slots for their own arg-save scratch, so dropping the COPY makes
; the subsequent LDA_DP read stale memory.  Caught by `g = g/x`
; Newton loop: iter-1's saved x_ml at $D0 was never actually written
; because MCP dropped the COPY, so iter-2's call to __divdf3 read
; garbage as its x_ml argument.  See feedback_jslpseudo_libcall_img_clobber.md.
;
; Fix: disable MachineCopyPropagation in addPostRegAlloc.
;
; Symptom shape we pin: for an i64-first-arg double function that
; calls a libcall, the entry must contain BOTH `stx 0xd?` AND `sta
; 0xd?` (for I64FirstArg's Img16 arg-save dance) — and they must
; survive to the asm output.  Without the MCP-disable, only one of
; those (or neither) appears.
;
; RUN: llc -mtriple=w65816 -O2 < %s | FileCheck %s

declare double @ext_div(double %a, double %b)

define double @div_chain(double %x) {
; CHECK-LABEL: div_chain:
; Img16 arg-save at function entry — both halves must reach asm:
; CHECK:       stx 0xd
; CHECK:       sta 0xd
; CHECK:       jsl ext_div
; CHECK:       rtl
entry:
  %r = call double @ext_div(double %x, double %x)
  ret double %r
}