| 1 | //===----------------------------------------------------------------------===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | |
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| 9 | #include "PassDetail.h" |
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| 10 | #include "mlir/Dialect/Func/IR/FuncOps.h" |
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| 11 | #include "mlir/IR/PatternMatch.h" |
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| 12 | #include "mlir/Support/LogicalResult.h" |
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| 13 | #include "mlir/Transforms/DialectConversion.h" |
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| 14 | #include "mlir/Transforms/GreedyPatternRewriteDriver.h" |
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| 15 | #include "clang/CIR/Dialect/IR/CIRDialect.h" |
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| 16 | #include "clang/CIR/Dialect/Passes.h" |
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| 17 | #include "clang/CIR/MissingFeatures.h" |
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| 18 | #include "llvm/Support/TimeProfiler.h" |
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| 19 | |
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| 20 | using namespace mlir; |
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| 21 | using namespace cir; |
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| 22 | |
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| 23 | namespace { |
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| 24 | |
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| 25 | struct HoistAllocasPass : public HoistAllocasBase<HoistAllocasPass> { |
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| 26 | |
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| 27 | HoistAllocasPass() = default; |
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| 28 | void runOnOperation() override; |
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| 29 | }; |
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| 30 | |
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| 31 | static void process(mlir::ModuleOp mod, cir::FuncOp func) { |
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| 32 | if (func.getRegion().empty()) |
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| 33 | return; |
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| 34 | |
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| 35 | // Hoist all static allocas to the entry block. |
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| 36 | mlir::Block &entryBlock = func.getRegion().front(); |
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| 37 | mlir::Operation *insertPoint = &*entryBlock.begin(); |
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| 38 | |
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| 39 | // Post-order is the default, but the code below requires it, so |
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| 40 | // let's not depend on the default staying that way. |
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| 41 | func.getBody().walk<mlir::WalkOrder::PostOrder>([&](cir::AllocaOp alloca) { |
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| 42 | if (alloca->getBlock() == &entryBlock) |
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| 43 | return; |
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| 44 | // Don't hoist allocas with dynamic alloca size. |
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| 45 | assert(!cir::MissingFeatures::opAllocaDynAllocSize()); |
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| 46 | |
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| 47 | // Hoist allocas into the entry block. |
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| 48 | |
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| 49 | // Preserving the `const` attribute on hoisted allocas can cause LLVM to |
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| 50 | // incorrectly introduce invariant group metadata in some circumstances. |
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| 51 | // The incubator performs some analysis to determine whether the attribute |
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| 52 | // can be preserved, but it only runs this analysis when optimizations are |
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| 53 | // enabled. Until we start tracking the optimization level, we can just |
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| 54 | // always remove the `const` attribute. |
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| 55 | assert(!cir::MissingFeatures::optInfoAttr()); |
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| 56 | if (alloca.getConstant()) |
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| 57 | alloca.setConstant(false); |
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| 58 | |
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| 59 | alloca->moveBefore(insertPoint); |
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| 60 | }); |
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| 61 | } |
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| 62 | |
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| 63 | void HoistAllocasPass::runOnOperation() { |
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| 64 | llvm::TimeTraceScope scope("Hoist Allocas" ); |
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| 65 | llvm::SmallVector<Operation *, 16> ops; |
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| 66 | |
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| 67 | Operation *op = getOperation(); |
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| 68 | auto mod = mlir::dyn_cast<mlir::ModuleOp>(op); |
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| 69 | if (!mod) |
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| 70 | mod = op->getParentOfType<mlir::ModuleOp>(); |
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| 71 | |
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| 72 | // If we ever introduce nested cir.function ops, we'll need to make this |
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| 73 | // walk in post-order and recurse into nested functions. |
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| 74 | getOperation()->walk<mlir::WalkOrder::PreOrder>([&](cir::FuncOp op) { |
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| 75 | process(mod, op); |
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| 76 | return mlir::WalkResult::skip(); |
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| 77 | }); |
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| 78 | } |
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| 79 | |
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| 80 | } // namespace |
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| 81 | |
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| 82 | std::unique_ptr<Pass> mlir::createHoistAllocasPass() { |
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| 83 | return std::make_unique<HoistAllocasPass>(); |
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| 84 | } |
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| 85 | |
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