Add no-inline attribute

Author: wsmoses

mlir/include/mlir/Dialect/Func/IR/FuncOps.td

@@ -98,6 +98,10 @@ def CallOp : Func_Op<"call",
     void setCalleeFromCallable(CallInterfaceCallable callee) {
       (*this)->setAttr("callee", callee.get<SymbolRefAttr>());
     }
+
+    bool legalToInline() {
+      return !(*this)->hasAttr("noinline");
+    }
   }];
 
   let assemblyFormat = [{

mlir/include/mlir/Interfaces/CallInterfaces.td

@@ -80,6 +80,16 @@ def CallOpInterface : OpInterface<"CallOpInterface"> {
       /*methodBody=*/[{}], /*defaultImplementation=*/[{
         return ::mlir::call_interface_impl::resolveCallable($_op);
       }]
+    >,
+    InterfaceMethod<[{
+        Return whether a given call is legal to inline or not (assuming all other requirements are met,
+        like the callee is direct, the parent region supports multiple blocks and the resolved, etc).
+        This can be used to implement a `noinline`-like attribute.
+    }],
+      "bool", "legalToInline", (ins),
+      /*methodBody=*/[{}], /*defaultImplementation=*/[{
+        return true;
+      }]
     >
   ];
 }

mlir/lib/Transforms/Utils/Inliner.cpp

@@ -712,6 +712,10 @@ bool Inliner::Impl::shouldInline(ResolvedCall &resolvedCall) {
   if (resolvedCall.call->hasTrait<OpTrait::IsTerminator>())
     return false;
 
+  // Don't inline calls which explicitly forbit inlining.
+  if (!resolvedCall.call.legalToInline())
+    return false;
+
   // Don't allow inlining if the target is a self-recursive function.
   if (llvm::count_if(*resolvedCall.targetNode,
                      [&](CallGraphNode::Edge const &edge) -> bool {

mlir/test/Transforms/inlining.mlir

@@ -19,6 +19,15 @@ func.func @inline_with_arg(%arg0 : i32) -> i32 {
   return %0 : i32
 }
 
+// CHECK-LABEL: func @noinline_with_arg
+func.func @noinline_with_arg(%arg0 : i32) -> i32 {
+  // CHECK-NEXT: func_with_arg
+  // CHECK-NEXT: return
+
+  %0 = call @func_with_arg(%arg0) {"noinline"=""} : (i32) -> i32
+  return %0 : i32
+}
+
 // Inline a function that has multiple return operations.
 func.func @func_with_multi_return(%a : i1) -> (i32) {
   cf.cond_br %a, ^bb1, ^bb2