[Mlir-commits] [mlir] a6b58e0 - [mlir][acc] Add ignore-default-none option to ACCImplicitData (#202442)

[llvmlistbot at llvm.org]

Author: Razvan Lupusoru
Date: 2026-06-10T07:07:16-07:00
New Revision: a6b58e00ceddef9c363fa8e19eb2ab530d0d9658

URL: https://github.com/llvm/llvm-project/commit/a6b58e00ceddef9c363fa8e19eb2ab530d0d9658
DIFF: https://github.com/llvm/llvm-project/commit/a6b58e00ceddef9c363fa8e19eb2ab530d0d9658.diff

LOG: [mlir][acc] Add ignore-default-none option to ACCImplicitData (#202442)

ACCImplicitData currently skips implicit data mapping when a visible
default(none) clause is present, per the OpenACC rule that no implicit
data attributes apply in that case.

That default is reasonable when a frontend already verifies
default(none) and ensures all user variables have an explicit data
clause. Without that checking, generating implicit mappings would risk
silently mapping user variables that should have been explicit under
default(none).

There are still cases where implicit mapping is needed even with
default(none):
- The frontend reports default(none) violations as warnings and
compilation continues, so some user variables may reach this pass
without explicit data clauses and still need implicit mapping.
- Compiler-generated temps or interior pointers may be live-in to the
region and still require implicit mapping even when all user variables
are already explicitly mapped.

In those cases, skipping implicit data entirely is too conservative.

Add an ignore-default-none pass option (default: false) to generate
implicit data mappings even when default(none) is present.

Added: 
    mlir/test/Dialect/OpenACC/acc-implicit-data-defaultnone.mlir

Modified: 
    mlir/include/mlir/Dialect/OpenACC/Transforms/Passes.td
    mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp

Removed: 
    


################################################################################
diff  --git a/mlir/include/mlir/Dialect/OpenACC/Transforms/Passes.td b/mlir/include/mlir/Dialect/OpenACC/Transforms/Passes.td
index 786d338cea600..485f68dfc9338 100644
--- a/mlir/include/mlir/Dialect/OpenACC/Transforms/Passes.td
+++ b/mlir/include/mlir/Dialect/OpenACC/Transforms/Passes.td
@@ -79,7 +79,14 @@ def ACCImplicitData : Pass<"acc-implicit-data", "mlir::ModuleOp"> {
            "variables between combined constructs (e.g., 'parallel loop') and "
            "separate constructs (e.g., 'parallel' followed by 'loop'), where "
            "the OpenACC spec requires copy semantics for the former but "
-           "firstprivate would normally apply for the latter.">
+           "firstprivate would normally apply for the latter.">,
+    Option<"ignoreDefaultNone", "ignore-default-none", "bool", "false",
+           "When disabled (default), if the region has a default(none) clause, "
+           "this pass does not generate implicit data attributes. When enabled, "
+           "implicit data is generated even with default(none). This is useful "
+           "when the frontend has robust default(none) verification: user "
+           "variables are already verified, so any remaining live-ins are "
+           "variables that still need mapping handling.">
   ];
 }
 

diff  --git a/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp b/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp
index 2de714ffcbc35..628454905b488 100644
--- a/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp
+++ b/mlir/lib/Dialect/OpenACC/Transforms/ACCImplicitData.cpp
@@ -708,12 +708,14 @@ void ACCImplicitData::generateImplicitDataOps(
     std::optional<acc::ClauseDefaultValue> &defaultClause,
     acc::OpenACCSupport &accSupport) {
   // Implicit data attributes are only applied if "[t]here is no default(none)
-  // clause visible at the compute construct."
-  if (defaultClause.has_value() &&
+  // clause visible at the compute construct", unless ignoreDefaultNone is set.
+  if (!ignoreDefaultNone && defaultClause.has_value() &&
       defaultClause.value() == acc::ClauseDefaultValue::None)
     return;
   assert(!defaultClause.has_value() ||
-         defaultClause.value() == acc::ClauseDefaultValue::Present);
+         defaultClause.value() == acc::ClauseDefaultValue::Present ||
+         (ignoreDefaultNone &&
+          defaultClause.value() == acc::ClauseDefaultValue::None));
 
   // 1) Collect live-in values.
   Region &accRegion = computeConstructOp->getRegion(0);

diff  --git a/mlir/test/Dialect/OpenACC/acc-implicit-data-defaultnone.mlir b/mlir/test/Dialect/OpenACC/acc-implicit-data-defaultnone.mlir
new file mode 100644
index 0000000000000..c8e550af001cf
--- /dev/null
+++ b/mlir/test/Dialect/OpenACC/acc-implicit-data-defaultnone.mlir
@@ -0,0 +1,23 @@
+// RUN: mlir-opt %s -acc-implicit-data=ignore-default-none=false -split-input-file | FileCheck %s
+// RUN: mlir-opt %s -acc-implicit-data=ignore-default-none=true -split-input-file | FileCheck %s --check-prefix=ENABLED
+
+// -----
+
+// Test scalar in parallel with default(none) - should NOT generate implicit
+// data when ignore-default-none is disabled. Otherwise, it should generate
+// implicit firstprivate.
+func.func @test_scalar_parallel_defaultnone() {
+  %alloc = memref.alloca() : memref<f32>
+  acc.parallel {
+    %load = memref.load %alloc[] : memref<f32>
+    acc.yield
+  } attributes {defaultAttr = #acc<defaultvalue none>}
+  return
+}
+
+// CHECK-LABEL: func.func @test_scalar_parallel_defaultnone
+// CHECK-NOT: acc.firstprivate
+// CHECK-NOT: acc.copyin
+
+// ENABLED-LABEL: func.func @test_scalar_parallel_defaultnone
+// ENABLED: acc.firstprivate varPtr({{.*}} : memref<f32>) recipe({{.*}}) -> memref<f32> {implicit = true, name = ""}