[MachineOutliner] Don't outline functions starting with PATCHABLE_FUNCTION_ENTER/FENTRL_CALL

MachineOutliner may outline a "patchable-function-entry" function whose body has
a TargetOpcode::PATCHABLE_FUNCTION_ENTER MachineInstr. This is incorrect because
the special code sequence must stay unchanged to be used at run-time.
Avoid outlining PATCHABLE_FUNCTION_ENTER. While here, avoid outlining FENTRY_CALL too
(which doesn't reproduce currently) to allow phase ordering flexibility.

Fixes #52635

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D115614

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetInstrInfo.cpp b/llvm/lib/CodeGen/TargetInstrInfo.cpp
index 6dd4dc2..3f22cc4 100644
--- a/llvm/lib/CodeGen/TargetInstrInfo.cpp
+++ b/llvm/lib/CodeGen/TargetInstrInfo.cpp
@@ -1418,3 +1418,16 @@ void TargetInstrInfo::mergeOutliningCandidateAttributes(
       }))
     F.addFnAttr(Attribute::NoUnwind);
 }
+
+bool TargetInstrInfo::isMBBSafeToOutlineFrom(MachineBasicBlock &MBB,
+                                             unsigned &Flags) const {
+  // Some instrumentations create special TargetOpcode at the start which
+  // expands to special code sequences which must be present.
+  auto First = MBB.getFirstNonDebugInstr();
+  if (First != MBB.end() &&
+      (First->getOpcode() == TargetOpcode::FENTRY_CALL ||
+       First->getOpcode() == TargetOpcode::PATCHABLE_FUNCTION_ENTER))
+    return false;
+
+  return true;
+}