[llvm] [CodeGen][ARM64EC] Add support for hybrid_patchable attribute. (PR #92965)

[Eli Friedman via llvm-commits]

================
@@ -615,6 +623,66 @@ Function *AArch64Arm64ECCallLowering::buildGuestExitThunk(Function *F) {
   return GuestExit;
 }
 
+Function *
+AArch64Arm64ECCallLowering::buildPatchableThunk(GlobalAlias *UnmangledAlias,
+                                                GlobalAlias *MangledAlias) {
+  llvm::raw_null_ostream NullThunkName;
+  FunctionType *Arm64Ty, *X64Ty;
+  Function *F = cast<Function>(MangledAlias->getAliasee());
+  getThunkType(F->getFunctionType(), F->getAttributes(),
+               Arm64ECThunkType::GuestExit, NullThunkName, Arm64Ty, X64Ty);
+  std::string ThunkName(MangledAlias->getName());
+  if (ThunkName[0] == '?' && ThunkName.find("@") != std::string::npos) {
+    ThunkName.insert(ThunkName.find("@"), "$hybpatch_thunk");
+  } else {
+    ThunkName.append("$hybpatch_thunk");
+  }
+
+  Function *GuestExit =
+      Function::Create(Arm64Ty, GlobalValue::WeakODRLinkage, 0, ThunkName, M);
+  GuestExit->setComdat(M->getOrInsertComdat(ThunkName));
+  GuestExit->setSection(".wowthk$aa");
+  BasicBlock *BB = BasicBlock::Create(M->getContext(), "", GuestExit);
+  IRBuilder<> B(BB);
+
+  // Load the global symbol as a pointer to the check function.
+  LoadInst *DispatchLoad = B.CreateLoad(DispatchFnPtrType, DispatchFnGlobal);
+
+  // Create new dispatch call instruction.
+  Function *ExitThunk =
+      buildExitThunk(F->getFunctionType(), F->getAttributes());
+  CallInst *Dispatch = B.CreateCall(
+      DispatchFnType, DispatchLoad,
+      {B.CreateBitCast(UnmangledAlias, B.getPtrTy()),
----------------
efriedma-quic wrote:

These bitcasts aren't necessary anymore with opaque pointers; probably I should go through and clean them all up.

https://github.com/llvm/llvm-project/pull/92965