[flang][cuf] Add to cuf.alloc/cuf.allocate mem alloc effect (#167414)

Add MemAlloc effect to the result so that cuf.alloc/cuf.allocate can be
recognized by FIR alias analysis.

Author: SusanTan

flang/include/flang/Optimizer/Dialect/CUF/CUFOps.td

@@ -26,8 +26,7 @@ include "mlir/IR/BuiltinAttributes.td"
 class cuf_Op<string mnemonic, list<Trait> traits>
     : Op<CUFDialect, mnemonic, traits>;
 
-def cuf_AllocOp : cuf_Op<"alloc", [AttrSizedOperandSegments,
-    MemoryEffects<[MemAlloc]>]> {
+def cuf_AllocOp : cuf_Op<"alloc", [AttrSizedOperandSegments]> {
   let summary = "Allocate an object on device";
 
   let description = [{
@@ -47,7 +46,9 @@ def cuf_AllocOp : cuf_Op<"alloc", [AttrSizedOperandSegments,
     cuf_DataAttributeAttr:$data_attr
   );
 
-  let results = (outs fir_ReferenceType:$ptr);
+  // Value-scoped Allocate on the returned reference
+  let results =
+      (outs Res<fir_ReferenceType, "", [MemAlloc<DefaultResource>]>:$ptr);
 
   let assemblyFormat = [{
     $in_type (`(` $typeparams^ `:` type($typeparams) `)`)?

flang/test/Analysis/AliasAnalysis/cuf-alloc-source-kind.mlir

@@ -0,0 +1,22 @@
+// REQUIRES: asserts
+// RUN: fir-opt %s -pass-pipeline='builtin.module(func.func(test-fir-alias-analysis))' -debug-only=fir-alias-analysis --mlir-disable-threading 2>&1 | FileCheck %s
+
+// Verify that a CUF allocation is recognized as SourceKind::Allocate by
+// fir::AliasAnalysis::getSource.
+
+module {
+  func.func @_QQmain() attributes {fir.bindc_name = "TEST"} {
+    // Allocate two independent device arrays and tag the results; with
+    // value-scoped MemAlloc handling in AA, these should be classified as
+    // Allocate and not alias.
+    %a = cuf.alloc !fir.box<!fir.heap<!fir.array<?xf32>>> {bindc_name = "a1", data_attr = #cuf.cuda<device>, uniq_name = "_QFEa1", test.ptr = "cuf_alloc_a"} -> !fir.ref<!fir.box<!fir.heap<!fir.array<?xf32>>>>
+    %b = cuf.alloc !fir.box<!fir.heap<!fir.array<?xf32>>> {bindc_name = "a2", data_attr = #cuf.cuda<device>, uniq_name = "_QFEa2", test.ptr = "cuf_alloc_b"} -> !fir.ref<!fir.box<!fir.heap<!fir.array<?xf32>>>>
+    return
+  }
+}
+
+// CHECK-LABEL: Testing : "_QQmain"
+// Distinct allocations should not alias.
+// CHECK: cuf_alloc_a#0 <-> cuf_alloc_b#0: NoAlias
+
+