[flang-commits] [flang] [flang] Inline hlfir.copy_in for trivial types (PR #138718)

[Slava Zakharin via flang-commits]

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+//===- InlineHLFIRCopyIn.cpp - Inline hlfir.copy_in ops -------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// Transform hlfir.copy_in array operations into loop nests performing element
+// per element assignments. For simplicity, the inlining is done for trivial
+// data types when the copy_in does not require a corresponding copy_out and
+// when the input array is not behind a pointer. This may change in the future.
+//===----------------------------------------------------------------------===//
+
+#include "flang/Optimizer/Builder/FIRBuilder.h"
+#include "flang/Optimizer/Builder/HLFIRTools.h"
+#include "flang/Optimizer/Dialect/FIRType.h"
+#include "flang/Optimizer/HLFIR/HLFIROps.h"
+#include "flang/Optimizer/OpenMP/Passes.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Support/LLVM.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+
+namespace hlfir {
+#define GEN_PASS_DEF_INLINEHLFIRCOPYIN
+#include "flang/Optimizer/HLFIR/Passes.h.inc"
+} // namespace hlfir
+
+#define DEBUG_TYPE "inline-hlfir-copy-in"
+
+static llvm::cl::opt<bool> noInlineHLFIRCopyIn(
+    "no-inline-hlfir-copy-in",
+    llvm::cl::desc("Do not inline hlfir.copy_in operations"),
+    llvm::cl::init(false));
+
+namespace {
+class InlineCopyInConversion : public mlir::OpRewritePattern<hlfir::CopyInOp> {
+public:
+  using mlir::OpRewritePattern<hlfir::CopyInOp>::OpRewritePattern;
+
+  llvm::LogicalResult
+  matchAndRewrite(hlfir::CopyInOp copyIn,
+                  mlir::PatternRewriter &rewriter) const override;
+};
+
+llvm::LogicalResult
+InlineCopyInConversion::matchAndRewrite(hlfir::CopyInOp copyIn,
+                                        mlir::PatternRewriter &rewriter) const {
+  fir::FirOpBuilder builder(rewriter, copyIn.getOperation());
+  mlir::Location loc = copyIn.getLoc();
+  hlfir::Entity inputVariable{copyIn.getVar()};
+  if (!fir::isa_trivial(inputVariable.getFortranElementType()))
+    return rewriter.notifyMatchFailure(copyIn,
+                                       "CopyInOp's data type is not trivial");
+
+  if (fir::isPointerType(inputVariable.getType()))
+    return rewriter.notifyMatchFailure(
+        copyIn, "CopyInOp's input variable is a pointer");
+
+  // There should be exactly one user of WasCopied - the corresponding
+  // CopyOutOp.
+  if (copyIn.getWasCopied().getUses().empty())
+    return rewriter.notifyMatchFailure(copyIn,
+                                       "CopyInOp's WasCopied has no uses");
+  // The copy out should always be present, either to actually copy or just
+  // deallocate memory.
+  auto copyOut = mlir::dyn_cast<hlfir::CopyOutOp>(
+      copyIn.getWasCopied().getUsers().begin().getCurrent().getUser());
+
+  if (!copyOut)
+    return rewriter.notifyMatchFailure(copyIn,
+                                       "CopyInOp has no direct CopyOut");
+
+  // Only inline the copy_in when copy_out does not need to be done, i.e. in
+  // case of intent(in).
+  if (copyOut.getVar())
+    return rewriter.notifyMatchFailure(copyIn, "CopyIn needs a copy-out");
+
+  inputVariable =
+      hlfir::derefPointersAndAllocatables(loc, builder, inputVariable);
+  mlir::Type resultAddrType = copyIn.getCopiedIn().getType();
+  mlir::Value isContiguous =
+      builder.create<fir::IsContiguousBoxOp>(loc, inputVariable);
+  mlir::Operation::result_range results =
+      builder
+          .genIfOp(loc, {resultAddrType, builder.getI1Type()}, isContiguous,
+                   /*withElseRegion=*/true)
+          .genThen([&]() {
+            mlir::Value falseVal = builder.create<mlir::arith::ConstantOp>(
+                loc, builder.getI1Type(), builder.getBoolAttr(false));
+            builder.create<fir::ResultOp>(
+                loc, mlir::ValueRange{inputVariable, falseVal});
+          })
+          .genElse([&] {
+            auto [temp, cleanup] =
+                hlfir::createTempFromMold(loc, builder, inputVariable);
+            mlir::Value shape = hlfir::genShape(loc, builder, inputVariable);
+            llvm::SmallVector<mlir::Value> extents =
+                hlfir::getIndexExtents(loc, builder, shape);
+            hlfir::LoopNest loopNest = hlfir::genLoopNest(
+                loc, builder, extents, /*isUnordered=*/true,
+                flangomp::shouldUseWorkshareLowering(copyIn));
+            builder.setInsertionPointToStart(loopNest.body);
+            hlfir::Entity elem = hlfir::getElementAt(
+                loc, builder, inputVariable, loopNest.oneBasedIndices);
+            elem = hlfir::loadTrivialScalar(loc, builder, elem);
+            hlfir::Entity tempElem = hlfir::getElementAt(
+                loc, builder, temp, loopNest.oneBasedIndices);
+            builder.create<hlfir::AssignOp>(loc, elem, tempElem);
+            builder.setInsertionPointAfter(loopNest.outerOp);
+
+            mlir::Value result;
+            // Make sure the result is always a boxed array by boxing it
+            // ourselves if need be.
+            if (mlir::isa<fir::BaseBoxType>(temp.getType())) {
+              result = temp;
+            } else {
+              fir::ReferenceType refTy =
+                  fir::ReferenceType::get(temp.getElementOrSequenceType());
+              mlir::Value refVal = builder.createConvert(loc, refTy, temp);
+              result =
+                  builder.create<fir::EmboxOp>(loc, resultAddrType, refVal);
+            }
+
+            builder.create<fir::ResultOp>(loc,
+                                          mlir::ValueRange{result, cleanup});
+          })
+          .getResults();
+
+  mlir::OpResult addr = results[0];
+  mlir::OpResult needsCleanup = results[1];
+
+  builder.setInsertionPoint(copyOut);
+  builder.genIfOp(loc, {}, needsCleanup, /*withElseRegion=*/false).genThen([&] {
+    auto boxAddr = builder.create<fir::BoxAddrOp>(loc, addr);
+    fir::HeapType heapType =
+        fir::HeapType::get(fir::BoxValue(addr).getBaseTy());
+    mlir::Value heapVal =
+        builder.createConvert(loc, heapType, boxAddr.getResult());
+    builder.create<fir::FreeMemOp>(loc, heapVal);
+  });
+  rewriter.eraseOp(copyOut);
+
+  mlir::Value tempBox = copyIn.getTempBox();
+
+  rewriter.replaceOp(copyIn, {addr, builder.genNot(loc, isContiguous)});
+
+  // The TempBox is only needed for flang-rt calls which we're no longer
+  // generating. It should have no uses left at this stage.
+  if (!tempBox.getUses().empty())
+    return mlir::failure();
----------------
vzakhari wrote:

I am not sure if it is correct to return `failure` here after the rewrites made above.

I think we should not bother about getting rid of the temporary alloca here.  It does not seem to be a part of this pass.

https://github.com/llvm/llvm-project/pull/138718