[BOLT] Add function splitting lit test without runtime dependency

- Test uses lit and FileCheck to check if OpNegateRAState CFIs are
  generated in the correct location for function-splitting.
- Also fix a bug related to function-splitting.

Author: bgergely0

bolt/lib/Passes/InsertNegateRAStatePass.cpp

@@ -102,7 +102,8 @@ void InsertNegateRAState::coverFunctionFragmentStart(BinaryFunction &BF,
       });
   // If a function is already split in the input, the first FF can also start
   // with Signed state. This covers that scenario as well.
-  if (BC.MIB->isRASigned(*((*FirstNonEmpty)->begin()))) {
+  if (BC.MIB->isRASigned(*((*FirstNonEmpty)->begin())) ||
+      BC.MIB->isAuthenticating(*((*FirstNonEmpty)->begin()))) {
     BF.addCFIInstruction(*FirstNonEmpty, (*FirstNonEmpty)->begin(),
                          MCCFIInstruction::createNegateRAState(nullptr));
   }

bolt/test/AArch64/pacret-split-funcs.s

@@ -0,0 +1,56 @@
+# Checking that we generate an OpNegateRAState CFI after the split point,
+# when splitting a region with signed RA state.
+
+# REQUIRES: system-linux
+
+# RUN: %clang %cflags -o %t %s
+# RUN: %clang %s %cflags -Wl,-q -o %t
+# RUN: link_fdata --no-lbr %s %t %t.fdata
+# RUN: llvm-bolt %t -o %t.bolt --data %t.fdata -split-functions \
+# RUN: --print-only foo --print-split --print-all 2>&1 | FileCheck %s
+
+# Checking that we don't see any OpNegateRAState CFIs before the insertion pass.
+# CHECK-NOT: OpNegateRAState
+# CHECK: Binary Function "foo" after insert-negate-ra-state-pass
+
+# CHECK:       paciasp
+# CHECK-NEXT:  OpNegateRAState
+
+# CHECK: -------   HOT-COLD SPLIT POINT   -------
+
+# CHECK:         OpNegateRAState
+# CHECK-NEXT:    autiasp
+# CHECK-NEXT:    OpNegateRAState
+# CHECK-NEXT:    ret
+
+# CHECK:         autiasp
+# CHECK-NEXT:    OpNegateRAState
+# CHECK-NEXT:    ret
+
+# End of the insert-negate-ra-state-pass logs
+# CHECK: Binary Function "foo" after finalize-functions
+
+  .text
+  .globl  foo
+  .type foo, %function
+foo:
+.cfi_startproc
+.entry_bb:
+     paciasp
+    .cfi_negate_ra_state     // indicating that paciasp changed the RA state to signed
+# FDATA: 1 foo #.entry_bb# 10
+    cmp x0, #0
+    b.eq .Lcold_bb1
+    autiasp
+    .cfi_negate_ra_state     // indicating that autiasp changed the RA state to unsigned
+    ret
+    .cfi_negate_ra_state     // ret has unsigned RA state, but the next inst (autiasp) has signed RA state
+.Lcold_bb1:
+    autiasp
+    .cfi_negate_ra_state     // indicating that autiasp changed the RA state to unsigned
+    ret
+.cfi_endproc
+  .size foo, .-foo
+
+## Force relocation mode.
+.reloc 0, R_AARCH64_NONE