[mlir][llvm] Do not inline variadic functions

mlir/lib/Dialect/LLVMIR/IR/LLVMInlining.cpp

@@ -663,6 +663,10 @@ struct LLVMInlinerInterface : public DialectInlinerInterface {
                  << "Cannot inline: callable is not an LLVM::LLVMFuncOp\n");
       return false;
     }
+    if (funcOp.isVarArg()) {
+      LLVM_DEBUG(llvm::dbgs() << "Cannot inline: callable is variadic\n");
+      return false;
+    }
     // TODO: Generate aliasing metadata from noalias argument/result attributes.
     if (auto attrs = funcOp.getArgAttrs()) {
       for (DictionaryAttr attrDict : attrs->getAsRange<DictionaryAttr>()) {
@@ -704,7 +708,8 @@ struct LLVMInlinerInterface : public DialectInlinerInterface {
   }
 
   bool isLegalToInline(Operation *op, Region *, bool, IRMapping &) const final {
-    return true;
+    // The inliner cannot handle variadic function arguments.
+    return !isa<LLVM::VaStartOp>(op);
   }
 
   /// Handle the given inlined return by replacing it with a branch. This

mlir/test/Dialect/LLVMIR/inlining.mlir

@@ -644,3 +644,28 @@ llvm.func @caller(%ptr : !llvm.ptr) -> i32 {
   llvm.store %c5, %ptr { access_groups = [#caller] } : i32, !llvm.ptr
   llvm.return %0 : i32
 }
+
+// -----
+
+llvm.func @vararg_func(...) {
+  llvm.return
+}
+
+llvm.func @vararg_intrinrics() {
+  %0 = llvm.mlir.constant(1 : i32) : i32
+  %list = llvm.alloca %0 x !llvm.struct<"struct.va_list_opaque", (ptr)> : (i32) -> !llvm.ptr
+  // The vararg intinriscs should normally be part of a variadic function.
+  // However, this test uses a non-variadic function to ensure the presence of
+  // the intrinsic alone suffices to prevent inlining.
+  llvm.intr.vastart %list : !llvm.ptr
+  llvm.return
+}
+
+// CHECK-LABEL: func @caller
+llvm.func @caller() {
+  // CHECK-NEXT: llvm.call @vararg_func()
+  llvm.call @vararg_func() vararg(!llvm.func<void (...)>) : () -> ()
+  // CHECK-NEXT: llvm.call @vararg_intrinrics()
+  llvm.call @vararg_intrinrics() : () -> ()
+  llvm.return
+}