test/CodeGen/X86/branchfolding-atomic-mmo.ll

; NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 6
; RUN: llc -O2 -stop-after=branch-folder %s -o - | FileCheck %s

; BranchFolder tail-merge dedups MachineMemOperands using
; MachineMemOperand::operator==. That comparison must include atomic
; ordering and syncscope so that a `load atomic monotonic` is never
; treated as identical to a plain `load` from the same address. If the
; comparison ignored ordering, the two blocks below would be tail-merged
; into a single `(load (s32))` MMO and the monotonic ordering would be
; silently dropped from the resulting machine code.
;
; With the fix, BranchFolder still tail-merges the two identical
; MOV32rm instructions (their operands are identical), but
; cloneMergedMemRefs keeps both MMOs because they differ in atomic
; ordering. Downstream passes therefore see the more-restrictive
; monotonic ordering and cannot reorder past synchronization points.

target triple = "x86_64-unknown-linux-gnu"

define i32 @no_drop_atomic_ordering(i1 %c, ptr %p) {
  ; CHECK-LABEL: name: no_drop_atomic_ordering
  ; CHECK: bb.0.entry:
  ; CHECK-NEXT:   liveins: $edi, $rsi
  ; CHECK-NEXT: {{  $}}
  ; CHECK-NEXT:   TEST8ri renamable $dil, 1, implicit-def $eflags, implicit killed $edi
  ; CHECK-NEXT:   renamable $eax = MOV32rm killed renamable $rsi, 1, $noreg, 0, $noreg :: (load (s32) from %ir.p), (load monotonic (s32) from %ir.p)
  ; CHECK-NEXT:   RET 0, $eax
entry:
  br i1 %c, label %a, label %b

a:
  %la = load atomic i32, ptr %p monotonic, align 4
  br label %end

b:
  %lb = load i32, ptr %p, align 4
  br label %end

end:
  %v = phi i32 [ %la, %a ], [ %lb, %b ]
  ret i32 %v
}