[flang-commits] [flang] [llvm] [mlir] [MLIR][OpenMP] Lowering nontemporal clause to LLVM IR for SIMD directive (PR #118751)

[Kaviya Rajendiran via flang-commits]

================
@@ -0,0 +1,71 @@
+//===- LowerNontemporal.cpp -------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Add nontemporal attributes to load and stores of variables marked as
+// nontemporal.
+//
+//===----------------------------------------------------------------------===//
+#include "flang/Optimizer/Dialect/FIROpsSupport.h"
+#include "flang/Optimizer/OpenMP/Passes.h"
+#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
+using namespace mlir;
+namespace flangomp {
+#define GEN_PASS_DEF_LOWERNONTEMPORALPASS
+#include "flang/Optimizer/OpenMP/Passes.h.inc"
+} // namespace flangomp
+namespace {
+class LowerNontemporalPass
+    : public flangomp::impl::LowerNontemporalPassBase<LowerNontemporalPass> {
+  void addNonTemporalAttr(omp::SimdOp simdOp) {
+    if (!simdOp.getNontemporalVars().empty()) {
+      llvm::SmallVector<mlir::Value> nontemporalOrigVars;
+      mlir::OperandRange nontemporals = simdOp.getNontemporalVars();
+      for (mlir::Value nontemporal : nontemporals) {
+        nontemporalOrigVars.push_back(nontemporal);
+      }
+      std::function<mlir::Value(mlir::Value)> getBaseOperand =
+          [&](mlir::Value operand) -> mlir::Value {
+        if (mlir::isa<fir::DeclareOp>(operand.getDefiningOp()))
+          return operand;
+        else if (auto arrayCoorOp = llvm::dyn_cast<fir::ArrayCoorOp>(
+                     operand.getDefiningOp())) {
+          return getBaseOperand(arrayCoorOp.getMemref());
+        } else if (auto boxAddrOp = llvm::dyn_cast<fir::BoxAddrOp>(
+                       operand.getDefiningOp())) {
+          return getBaseOperand(boxAddrOp.getVal());
+        } else if (auto loadOp =
+                       llvm::dyn_cast<fir::LoadOp>(operand.getDefiningOp())) {
+          return getBaseOperand(loadOp.getMemref());
+        } else {
+          return operand;
+        }
+      };
+      simdOp->walk([&](Operation *op) {
+        mlir::Value Operand = nullptr;
+        if (auto loadOp = llvm::dyn_cast<fir::LoadOp>(op)) {
+          Operand = loadOp.getMemref();
+        } else if (auto storeOp = llvm::dyn_cast<fir::StoreOp>(op)) {
+          Operand = storeOp.getMemref();
+        }
+        if (Operand && !(fir::isAllocatableType(Operand.getType()) ||
+                         fir::isPointerType((Operand.getType())))) {
+          Operand = getBaseOperand(Operand);
+          if (is_contained(nontemporalOrigVars, Operand)) {
+            // Set the attribute
+            op->setAttr("nontemporal", UnitAttr::get(op->getContext()));
----------------
kaviya2510 wrote:

I have a small doubt here.
You suggested adding a new attribute "nontemporal" to the LLVM dialect and using it in the pass to mark loads and stores accordingly. 
However, LLVM dialect already supports the nontemporal attribute on load and store operations. Can't we use the existing attribute instead of introducing a new one? 

Could you please help me understand this better?

https://github.com/llvm/llvm-project/pull/118751