ed07412888
This patch relies on #140235 and #139724 to speed-up compilations of files with derived type array global with initial value. Currently, such derived type global init was lowered to an llvm.mlir.insertvalue chain in the LLVM IR dialect because there was no way to represent such value via attributes. This chain was later folded in LLVM dialect to LLVM IR using LLVM IR (not dialect) folding. This insert chain generation and folding is very expensive for big arrays. For instance, this patch brings down the compilation of FM_lib fmsave.f95 from 50s to 0.5s.
211 lines
8.5 KiB
C++
211 lines
8.5 KiB
C++
//===-- LLVMInsertChainFolder.cpp -----------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "flang/Optimizer/CodeGen/LLVMInsertChainFolder.h"
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#include "mlir/Dialect/LLVMIR/LLVMAttrs.h"
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#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
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#include "mlir/IR/Builders.h"
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#include "llvm/Support/Debug.h"
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#define DEBUG_TYPE "flang-insert-folder"
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#include <deque>
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namespace {
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// Helper class to construct the attribute elements of an aggregate value being
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// folded without creating a full mlir::Attribute representation for each step
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// of the insert value chain, which would both be expensive in terms of
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// compilation time and memory (since the intermediate Attribute would survive,
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// unused, inside the mlir context).
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class InsertChainBackwardFolder {
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// Type for the current value of an element of the aggregate value being
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// constructed by the insert chain.
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// At any point of the insert chain, the value of an element is either:
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// - nullptr: not yet known, the insert has not yet been seen.
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// - an mlir::Attribute: the element is fully defined.
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// - a nested InsertChainBackwardFolder: the element is itself an aggregate
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// and its sub-elements have been partially defined (insert with mutliple
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// indices have been seen).
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// The insertion folder assumes backward walk of the insert chain. Once an
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// element or sub-element has been defined, it is not overriden by new
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// insertions (last insert wins).
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using InFlightValue =
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llvm::PointerUnion<mlir::Attribute, InsertChainBackwardFolder *>;
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public:
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InsertChainBackwardFolder(
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mlir::Type type, std::deque<InsertChainBackwardFolder> *folderStorage)
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: values(getNumElements(type), mlir::Attribute{}),
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folderStorage{folderStorage}, type{type} {}
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/// Push
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bool pushValue(mlir::Attribute val, llvm::ArrayRef<int64_t> at);
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mlir::Attribute finalize(mlir::Attribute defaultFieldValue);
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private:
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static int64_t getNumElements(mlir::Type type) {
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if (auto structTy =
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llvm::dyn_cast_if_present<mlir::LLVM::LLVMStructType>(type))
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return structTy.getBody().size();
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if (auto arrayTy =
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llvm::dyn_cast_if_present<mlir::LLVM::LLVMArrayType>(type))
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return arrayTy.getNumElements();
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return 0;
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}
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static mlir::Type getSubElementType(mlir::Type type, int64_t field) {
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if (auto arrayTy =
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llvm::dyn_cast_if_present<mlir::LLVM::LLVMArrayType>(type))
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return arrayTy.getElementType();
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if (auto structTy =
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llvm::dyn_cast_if_present<mlir::LLVM::LLVMStructType>(type))
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return structTy.getBody()[field];
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return nullptr;
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}
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// Current element value of the aggregate value being built.
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llvm::SmallVector<InFlightValue> values;
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// std::deque is used to allocate storage for nested list and guarantee the
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// stability of the InsertChainBackwardFolder* used as element value.
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std::deque<InsertChainBackwardFolder> *folderStorage;
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// Type of the aggregate value being built.
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mlir::Type type;
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};
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} // namespace
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// Helper to fold the value being inserted by an llvm.insert_value.
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// This may call tryFoldingLLVMInsertChain if the value is an aggregate and
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// was itself constructed by a different insert chain.
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// Returns a nullptr Attribute if the value could not be folded.
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static mlir::Attribute getAttrIfConstant(mlir::Value val,
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mlir::OpBuilder &rewriter) {
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if (auto cst = val.getDefiningOp<mlir::LLVM::ConstantOp>())
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return cst.getValue();
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if (auto insert = val.getDefiningOp<mlir::LLVM::InsertValueOp>()) {
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llvm::FailureOr<mlir::Attribute> attr =
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fir::tryFoldingLLVMInsertChain(val, rewriter);
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if (succeeded(attr))
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return *attr;
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return nullptr;
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}
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if (val.getDefiningOp<mlir::LLVM::ZeroOp>())
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return mlir::LLVM::ZeroAttr::get(val.getContext());
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if (val.getDefiningOp<mlir::LLVM::UndefOp>())
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return mlir::LLVM::UndefAttr::get(val.getContext());
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if (mlir::Operation *op = val.getDefiningOp()) {
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unsigned resNum = llvm::cast<mlir::OpResult>(val).getResultNumber();
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llvm::SmallVector<mlir::Value> results;
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if (mlir::succeeded(rewriter.tryFold(op, results)) &&
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results.size() > resNum) {
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if (auto cst = results[resNum].getDefiningOp<mlir::LLVM::ConstantOp>())
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return cst.getValue();
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}
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}
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if (auto trunc = val.getDefiningOp<mlir::LLVM::TruncOp>())
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if (auto attr = getAttrIfConstant(trunc.getArg(), rewriter))
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if (auto intAttr = llvm::dyn_cast<mlir::IntegerAttr>(attr))
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return mlir::IntegerAttr::get(trunc.getType(), intAttr.getInt());
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LLVM_DEBUG(llvm::dbgs() << "cannot fold insert value operand: " << val
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<< "\n");
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return nullptr;
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}
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mlir::Attribute
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InsertChainBackwardFolder::finalize(mlir::Attribute defaultFieldValue) {
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llvm::SmallVector<mlir::Attribute> attrs = llvm::map_to_vector(
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values, [&](InFlightValue inFlight) -> mlir::Attribute {
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if (!inFlight)
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return defaultFieldValue;
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if (auto attr = llvm::dyn_cast<mlir::Attribute>(inFlight))
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return attr;
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return llvm::cast<InsertChainBackwardFolder *>(inFlight)->finalize(
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defaultFieldValue);
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});
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return mlir::ArrayAttr::get(type.getContext(), attrs);
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}
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bool InsertChainBackwardFolder::pushValue(mlir::Attribute val,
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llvm::ArrayRef<int64_t> at) {
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if (at.size() == 0 || at[0] >= static_cast<int64_t>(values.size()))
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return false;
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InFlightValue &inFlight = values[at[0]];
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if (!inFlight) {
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if (at.size() == 1) {
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inFlight = val;
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return true;
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}
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// This is the first insert to a nested field. Create a
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// InsertChainBackwardFolder for the current element value.
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mlir::Type subType = getSubElementType(type, at[0]);
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if (!subType)
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return false;
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InsertChainBackwardFolder &inFlightList =
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folderStorage->emplace_back(subType, folderStorage);
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inFlight = &inFlightList;
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return inFlightList.pushValue(val, at.drop_front());
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}
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// Keep last inserted value if already set.
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if (llvm::isa<mlir::Attribute>(inFlight))
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return true;
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auto *inFlightList = llvm::cast<InsertChainBackwardFolder *>(inFlight);
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if (at.size() == 1) {
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if (!llvm::isa<mlir::LLVM::ZeroAttr, mlir::LLVM::UndefAttr>(val)) {
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LLVM_DEBUG(llvm::dbgs()
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<< "insert chain sub-element partially overwritten initial "
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"value is not zero or undef\n");
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return false;
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}
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inFlight = inFlightList->finalize(val);
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return true;
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}
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return inFlightList->pushValue(val, at.drop_front());
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}
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llvm::FailureOr<mlir::Attribute>
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fir::tryFoldingLLVMInsertChain(mlir::Value val, mlir::OpBuilder &rewriter) {
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if (auto cst = val.getDefiningOp<mlir::LLVM::ConstantOp>())
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return cst.getValue();
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if (auto insert = val.getDefiningOp<mlir::LLVM::InsertValueOp>()) {
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LLVM_DEBUG(llvm::dbgs() << "trying to fold insert chain:" << val << "\n");
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if (auto structTy =
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llvm::dyn_cast<mlir::LLVM::LLVMStructType>(insert.getType())) {
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mlir::LLVM::InsertValueOp currentInsert = insert;
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mlir::LLVM::InsertValueOp lastInsert;
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std::deque<InsertChainBackwardFolder> folderStorage;
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InsertChainBackwardFolder inFlightList(structTy, &folderStorage);
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while (currentInsert) {
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mlir::Attribute attr =
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getAttrIfConstant(currentInsert.getValue(), rewriter);
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if (!attr)
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return llvm::failure();
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if (!inFlightList.pushValue(attr, currentInsert.getPosition()))
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return llvm::failure();
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lastInsert = currentInsert;
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currentInsert = currentInsert.getContainer()
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.getDefiningOp<mlir::LLVM::InsertValueOp>();
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}
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mlir::Attribute defaultVal;
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if (lastInsert) {
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if (lastInsert.getContainer().getDefiningOp<mlir::LLVM::ZeroOp>())
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defaultVal = mlir::LLVM::ZeroAttr::get(val.getContext());
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else if (lastInsert.getContainer().getDefiningOp<mlir::LLVM::UndefOp>())
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defaultVal = mlir::LLVM::UndefAttr::get(val.getContext());
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}
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if (!defaultVal) {
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LLVM_DEBUG(llvm::dbgs()
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<< "insert chain initial value is not Zero or Undef\n");
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return llvm::failure();
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}
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return inFlightList.finalize(defaultVal);
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}
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}
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return llvm::failure();
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}
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