bff94d774c
Alloca operations were being emitted into the entry block of the current function unconditionally, even if the variable they represented was declared in a different scope. This change upstreams the code for handling insertion of the alloca into the proper lexcial scope. It also adds a CIR-to-CIR transformation to hoist allocas to the function entry block, which is necessary to produce the expected LLVM IR during lowering.
85 lines
2.8 KiB
C++
85 lines
2.8 KiB
C++
//===----------------------------------------------------------------------===//
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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 "PassDetail.h"
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#include "mlir/Dialect/Func/IR/FuncOps.h"
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#include "mlir/IR/PatternMatch.h"
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#include "mlir/Support/LogicalResult.h"
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#include "mlir/Transforms/DialectConversion.h"
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#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
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#include "clang/CIR/Dialect/IR/CIRDialect.h"
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#include "clang/CIR/Dialect/Passes.h"
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#include "clang/CIR/MissingFeatures.h"
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#include "llvm/Support/TimeProfiler.h"
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using namespace mlir;
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using namespace cir;
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namespace {
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struct HoistAllocasPass : public HoistAllocasBase<HoistAllocasPass> {
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HoistAllocasPass() = default;
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void runOnOperation() override;
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};
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static void process(mlir::ModuleOp mod, cir::FuncOp func) {
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if (func.getRegion().empty())
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return;
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// Hoist all static allocas to the entry block.
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mlir::Block &entryBlock = func.getRegion().front();
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mlir::Operation *insertPoint = &*entryBlock.begin();
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// Post-order is the default, but the code below requires it, so
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// let's not depend on the default staying that way.
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func.getBody().walk<mlir::WalkOrder::PostOrder>([&](cir::AllocaOp alloca) {
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if (alloca->getBlock() == &entryBlock)
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return;
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// Don't hoist allocas with dynamic alloca size.
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assert(!cir::MissingFeatures::opAllocaDynAllocSize());
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// Hoist allocas into the entry block.
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// Preserving the `const` attribute on hoisted allocas can cause LLVM to
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// incorrectly introduce invariant group metadata in some circumstances.
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// The incubator performs some analysis to determine whether the attribute
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// can be preserved, but it only runs this analysis when optimizations are
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// enabled. Until we start tracking the optimization level, we can just
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// always remove the `const` attribute.
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assert(!cir::MissingFeatures::optInfoAttr());
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if (alloca.getConstant())
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alloca.setConstant(false);
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alloca->moveBefore(insertPoint);
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});
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}
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void HoistAllocasPass::runOnOperation() {
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llvm::TimeTraceScope scope("Hoist Allocas");
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llvm::SmallVector<Operation *, 16> ops;
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Operation *op = getOperation();
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auto mod = mlir::dyn_cast<mlir::ModuleOp>(op);
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if (!mod)
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mod = op->getParentOfType<mlir::ModuleOp>();
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// If we ever introduce nested cir.function ops, we'll need to make this
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// walk in post-order and recurse into nested functions.
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getOperation()->walk<mlir::WalkOrder::PreOrder>([&](cir::FuncOp op) {
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process(mod, op);
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return mlir::WalkResult::skip();
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});
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}
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} // namespace
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std::unique_ptr<Pass> mlir::createHoistAllocasPass() {
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return std::make_unique<HoistAllocasPass>();
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}
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