[mlir][acc] Adds attr to acc.present to identify default clause origin (#169114)

The `acc.present` Op as generated by ACCImplicitData does not provide a
way to differentiate between `acc.present` ops that are generated
implicitly and the ones that are generated as result of an explicit
`default(present)` clause in the source code. This differentiation would
allow for better communication to the user on the decisions made by the
compiler while managing data automatically between the host and the
device. This commit adds this information as a discardable attribute on
the `acc.present` op.

Author: atmnp

flang/test/Transforms/OpenACC/acc-implicit-data.fir

@@ -133,7 +133,7 @@ func.func @test_fir_derivedtype_in_parallel_defaultpresent() {
   return
 }
 
-// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.type<_QFTaggr{field:f32}>>) -> !fir.ref<!fir.type<_QFTaggr{field:f32}>> {implicit = true, name = "aggrvar"}
+// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.type<_QFTaggr{field:f32}>>) -> !fir.ref<!fir.type<_QFTaggr{field:f32}>> {acc.from_default, implicit = true, name = "aggrvar"}
 // CHECK: acc.delete accPtr(%[[PRESENT]] : !fir.ref<!fir.type<_QFTaggr{field:f32}>>) {dataClause = #acc<data_clause acc_present>, implicit = true, name = "aggrvar"}
 
 // -----
@@ -147,7 +147,7 @@ func.func @test_fir_derivedtype_in_kernels_defaultpresent() {
   return
 }
 
-// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.type<_QFTaggr{field:f32}>>) -> !fir.ref<!fir.type<_QFTaggr{field:f32}>> {implicit = true, name = "aggrvar"}
+// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.type<_QFTaggr{field:f32}>>) -> !fir.ref<!fir.type<_QFTaggr{field:f32}>> {acc.from_default, implicit = true, name = "aggrvar"}
 // CHECK: acc.delete accPtr(%[[PRESENT]] : !fir.ref<!fir.type<_QFTaggr{field:f32}>>) {dataClause = #acc<data_clause acc_present>, implicit = true, name = "aggrvar"}
 
 // -----
@@ -161,7 +161,7 @@ func.func @test_fir_array_in_parallel_defaultpresent() {
   return
 }
 
-// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.array<10xf32>>) -> !fir.ref<!fir.array<10xf32>> {implicit = true, name = "arrayvar"}
+// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.array<10xf32>>) -> !fir.ref<!fir.array<10xf32>> {acc.from_default, implicit = true, name = "arrayvar"}
 // CHECK: acc.delete accPtr(%[[PRESENT]] : !fir.ref<!fir.array<10xf32>>) {dataClause = #acc<data_clause acc_present>, implicit = true, name = "arrayvar"}
 
 // -----
@@ -175,7 +175,7 @@ func.func @test_fir_array_in_kernels_defaultpresent() {
   return
 }
 
-// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.array<10xf32>>) -> !fir.ref<!fir.array<10xf32>> {implicit = true, name = "arrayvar"}
+// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : !fir.ref<!fir.array<10xf32>>) -> !fir.ref<!fir.array<10xf32>> {acc.from_default, implicit = true, name = "arrayvar"}
 // CHECK: acc.delete accPtr(%[[PRESENT]] : !fir.ref<!fir.array<10xf32>>) {dataClause = #acc<data_clause acc_present>, implicit = true, name = "arrayvar"}
 
 // -----

mlir/include/mlir/Dialect/OpenACC/OpenACC.h

@@ -177,6 +177,10 @@ static constexpr StringLiteral getRoutineInfoAttrName() {
   return StringLiteral("acc.routine_info");
 }
 
+static constexpr StringLiteral getFromDefaultClauseAttrName() {
+  return StringLiteral("acc.from_default");
+}
+
 static constexpr StringLiteral getVarNameAttrName() {
   return VarNameAttr::name;
 }

mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp

@@ -570,6 +570,8 @@ Operation *ACCImplicitData::generateDataClauseOpForCandidate(
       newDataOp = acc::PresentOp::create(builder, loc, var,
                                          /*structured=*/true, /*implicit=*/true,
                                          accSupport.getVariableName(var));
+      newDataOp->setAttr(acc::getFromDefaultClauseAttrName(),
+                         builder.getUnitAttr());
     } else {
       auto copyinOp =
           acc::CopyinOp::create(builder, loc, var,

mlir/test/Dialect/OpenACC/acc-implicit-data.mlir

@@ -110,7 +110,7 @@ func.func @test_array_parallel_defaultpresent() {
 }
 
 // CHECK-LABEL: func.func @test_array_parallel_defaultpresent
-// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : memref<10xf32>) -> memref<10xf32> {implicit = true, name = ""}
+// CHECK: %[[PRESENT:.*]] = acc.present varPtr({{.*}} : memref<10xf32>) -> memref<10xf32> {acc.from_default, implicit = true, name = ""}
 // CHECK: acc.delete accPtr(%[[PRESENT]] : memref<10xf32>) {dataClause = #acc<data_clause acc_present>, implicit = true, name = ""}
 
 // -----