test/CodeGen/X86/eflags-copy-expansion.mir

# RUN: llc -run-pass postrapseudos -mtriple=i386-apple-macosx -o - %s | FileCheck %s

# Verify that we correctly save and restore eax when copying eflags,
# even when only a smaller alias of eax is used. We used to check only
# eax and not its aliases.
# PR27624.

--- |
  target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"

  define void @foo() {
  entry:
    br label %false
  false:
    ret void
  }

...

---
name:            foo
tracksRegLiveness: true
liveins:
  - { reg: '%edi' }
body:             |
  bb.0.entry:
    liveins: %edi
    NOOP implicit-def %al

    ; The bug was triggered only when LivePhysReg is used, which
    ; happens only when the heuristic for the liveness computation
    ; failed. The liveness computation heuristic looks at 10 instructions
    ; before and after the copy. Make sure we do not reach the definition of
    ; AL in 10 instructions, otherwise the heuristic will see that it is live.
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    NOOP
    ; Save AL.
    ; CHECK: PUSH32r killed %eax

    ; Copy EDI into EFLAGS
    ; CHECK-NEXT: %eax = MOV32rr %edi
    ; CHECK-NEXT: %al = ADD8ri %al, 127, implicit-def %eflags
    ; CHECK-NEXT: SAHF implicit-def %eflags, implicit %ah
    %eflags = COPY %edi

    ; Restore AL.
    ; CHECK-NEXT: %eax = POP32r
  bb.1.false:
    liveins: %al
    NOOP implicit %al
    RETQ

...