llvm/test/CodeGen/X86/flags-copy-lowering-unreachable.mir

# RUN: llc -mtriple=x86_64-- -run-pass=x86-flags-copy-lowering -verify-machineinstrs -o - %s | FileCheck %s
#
# An EFLAGS copy stranded in a block that is unreachable from the entry must
# not trip the "Unlowered EFLAGS copy!" assertion. The pass collects copies to
# lower with a reverse-post-order traversal, which only visits reachable
# blocks, so such copies are intentionally left in place (a later pass removes
# the unreachable block). The verification at the end of the pass must use the
# same notion of reachability.
---
name:            stranded_eflags_copy
tracksRegLiveness: true
body:             |
  bb.0:
    RET 0

  ; bb.1 has no predecessors, so it is unreachable from bb.0. The save/recheck
  ; EFLAGS copies below are left untouched rather than crashing the pass.
  bb.1:
    ; CHECK-LABEL: bb.1:
    ; CHECK: %1:gr64 = COPY $eflags
    ; CHECK: $eflags = COPY %1
    %0:gr64 = IMPLICIT_DEF
    TEST64rr %0, %0, implicit-def $eflags
    %1:gr64 = COPY $eflags
    TEST64rr %0, %0, implicit-def $eflags
    $eflags = COPY %1
    SETCCm $noreg, 1, $noreg, 0, $noreg, 4, implicit $eflags :: (store (s8) into `ptr null`)
    RET 0
...