[Test] Add XFAIL test for PR56243

This test demonstrates how sinking down gc.relocate may lead to breach
of LCSSA form by tokens and, consecutively, end up with SSA breach by
LoopSimplifyCFG which creates fake edges and is unable to update missing
LCSSA phis for tokens used outside of the loop.

llvm/test/Transforms/LICM/pr56243.ll

@@ -0,0 +1,56 @@
+; RUN: opt -S -passes='loop-mssa(licm,loop-simplifycfg)' < %s | FileCheck %s
+
+; REQUIRES: asserts
+; XFAIL: *
+
+; Here we end un sinking a user of token down from the loop, therefore breaching LCSSA form.
+; Then, LoopSimplifyCFG expcets that LCSSA form is maintained, and remains unaware that
+; it may be penetrated by tokens. As result, it may end up breaking dominance between def and
+; use by introducing fake temporary edges.
+
+define i8 addrspace(1)* @test_gc_relocate() gc "statepoint-example" {
+; CHECK-LABEL: @test_gc_relocate
+  br label %bb1
+
+bb1:                                              ; preds = %bb45, %0
+  switch i32 undef, label %bb43 [
+    i32 1, label %bb18
+  ]
+
+bb18:                                             ; preds = %bb1
+  switch i32 undef, label %bb43 [
+    i32 0, label %bb28
+  ]
+
+bb28:                                             ; preds = %bb18
+  %tmp34 = call token (i64, i32, i8 addrspace(1)* (i64, i32, i32, i32)*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_p1i8i64i32i32i32f(i64 2882400000, i32 0, i8 addrspace(1)* (i64, i32, i32, i32)* nonnull elementtype(i8 addrspace(1)* (i64, i32, i32, i32)) @barney.4, i32 4, i32 0, i64 undef, i32 5, i32 5, i32 undef, i32 0, i32 0) [ "deopt"(), "gc-live"(i8 addrspace(1)* undef) ]
+  %tmp35 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token %tmp34, i32 0, i32 0) ; (undef, undef)
+  br i1 false, label %bb57, label %bb36
+
+bb36:                                             ; preds = %bb28
+  switch i32 undef, label %bb43 [
+    i32 1, label %bb39
+  ]
+
+bb39:                                             ; preds = %bb36
+  switch i32 undef, label %bb43 [
+    i32 1, label %bb45
+  ]
+
+bb43:                                             ; preds = %bb39, %bb36, %bb18, %bb1
+  unreachable
+
+bb45:                                             ; preds = %bb39
+  br label %bb1
+
+bb57:                                             ; preds = %bb28
+  ret i8 addrspace(1)* %tmp35
+}
+
+declare i8 addrspace(1)* @barney.4(i64, i32, i32, i32)
+
+declare i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token, i32 immarg, i32 immarg) #0
+
+declare token @llvm.experimental.gc.statepoint.p0f_p1i8i64i32i32i32f(i64 immarg, i32 immarg, i8 addrspace(1)* (i64, i32, i32, i32)*, i32 immarg, i32 immarg, ...)
+
+attributes #0 = { nounwind readnone }