48b126e30b
This commit changes intrinsics that have immarg parameter attributes to model these parameters as attributes, instead of operands. Using operands only works if the operation is an `llvm.mlir.constant`, otherwise the exported LLVMIR is invalid. Reviewed By: gysit Differential Revision: https://reviews.llvm.org/D151692
433 lines
19 KiB
C++
433 lines
19 KiB
C++
//===- LLVMInlining.cpp - LLVM inlining interface and logic -----*- 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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//
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// Logic for inlining LLVM functions and the definition of the
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// LLVMInliningInterface.
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//
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//===----------------------------------------------------------------------===//
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#include "LLVMInlining.h"
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#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
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#include "mlir/IR/Matchers.h"
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#include "mlir/Interfaces/DataLayoutInterfaces.h"
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#include "mlir/Transforms/InliningUtils.h"
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#include "llvm/Support/Debug.h"
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#define DEBUG_TYPE "llvm-inliner"
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using namespace mlir;
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/// Check whether the given alloca is an input to a lifetime intrinsic,
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/// optionally passing through one or more casts on the way. This is not
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/// transitive through block arguments.
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static bool hasLifetimeMarkers(LLVM::AllocaOp allocaOp) {
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SmallVector<Operation *> stack(allocaOp->getUsers().begin(),
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allocaOp->getUsers().end());
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while (!stack.empty()) {
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Operation *op = stack.pop_back_val();
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if (isa<LLVM::LifetimeStartOp, LLVM::LifetimeEndOp>(op))
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return true;
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if (isa<LLVM::BitcastOp>(op))
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stack.append(op->getUsers().begin(), op->getUsers().end());
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}
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return false;
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}
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/// Handles alloca operations in the inlined blocks:
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/// - Moves all alloca operations with a constant size in the former entry block
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/// of the callee into the entry block of the caller, so they become part of
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/// the function prologue/epilogue during code generation.
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/// - Inserts lifetime intrinsics that limit the scope of inlined static allocas
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/// to the inlined blocks.
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/// - Inserts StackSave and StackRestore operations if dynamic allocas were
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/// inlined.
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static void
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handleInlinedAllocas(Operation *call,
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iterator_range<Region::iterator> inlinedBlocks) {
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Block *calleeEntryBlock = &(*inlinedBlocks.begin());
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Block *callerEntryBlock = &(*calleeEntryBlock->getParent()->begin());
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if (calleeEntryBlock == callerEntryBlock)
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// Nothing to do.
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return;
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SmallVector<std::tuple<LLVM::AllocaOp, IntegerAttr, bool>> allocasToMove;
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bool shouldInsertLifetimes = false;
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bool hasDynamicAlloca = false;
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// Conservatively only move static alloca operations that are part of the
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// entry block and do not inspect nested regions, since they may execute
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// conditionally or have other unknown semantics.
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for (auto allocaOp : calleeEntryBlock->getOps<LLVM::AllocaOp>()) {
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IntegerAttr arraySize;
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if (!matchPattern(allocaOp.getArraySize(), m_Constant(&arraySize))) {
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hasDynamicAlloca = true;
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continue;
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}
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bool shouldInsertLifetime =
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arraySize.getValue() != 0 && !hasLifetimeMarkers(allocaOp);
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shouldInsertLifetimes |= shouldInsertLifetime;
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allocasToMove.emplace_back(allocaOp, arraySize, shouldInsertLifetime);
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}
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// Check the remaining inlined blocks for dynamic allocas as well.
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for (Block &block : llvm::drop_begin(inlinedBlocks)) {
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if (hasDynamicAlloca)
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break;
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hasDynamicAlloca =
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llvm::any_of(block.getOps<LLVM::AllocaOp>(), [](auto allocaOp) {
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return !matchPattern(allocaOp.getArraySize(), m_Constant());
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});
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}
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if (allocasToMove.empty() && !hasDynamicAlloca)
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return;
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OpBuilder builder(calleeEntryBlock, calleeEntryBlock->begin());
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Value stackPtr;
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if (hasDynamicAlloca) {
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// This may result in multiple stacksave/stackrestore intrinsics in the same
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// scope if some are already present in the body of the caller. This is not
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// invalid IR, but LLVM cleans these up in InstCombineCalls.cpp, along with
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// other cases where the stacksave/stackrestore is redundant.
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stackPtr = builder.create<LLVM::StackSaveOp>(
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call->getLoc(), LLVM::LLVMPointerType::get(call->getContext()));
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}
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builder.setInsertionPoint(callerEntryBlock, callerEntryBlock->begin());
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for (auto &[allocaOp, arraySize, shouldInsertLifetime] : allocasToMove) {
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auto newConstant = builder.create<LLVM::ConstantOp>(
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allocaOp->getLoc(), allocaOp.getArraySize().getType(), arraySize);
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// Insert a lifetime start intrinsic where the alloca was before moving it.
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if (shouldInsertLifetime) {
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OpBuilder::InsertionGuard insertionGuard(builder);
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builder.setInsertionPoint(allocaOp);
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builder.create<LLVM::LifetimeStartOp>(
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allocaOp.getLoc(), arraySize.getValue().getLimitedValue(),
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allocaOp.getResult());
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}
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allocaOp->moveAfter(newConstant);
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allocaOp.getArraySizeMutable().assign(newConstant.getResult());
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}
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if (!shouldInsertLifetimes && !hasDynamicAlloca)
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return;
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// Insert a lifetime end intrinsic before each return in the callee function.
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for (Block &block : inlinedBlocks) {
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if (!block.getTerminator()->hasTrait<OpTrait::ReturnLike>())
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continue;
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builder.setInsertionPoint(block.getTerminator());
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if (hasDynamicAlloca)
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builder.create<LLVM::StackRestoreOp>(call->getLoc(), stackPtr);
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for (auto &[allocaOp, arraySize, shouldInsertLifetime] : allocasToMove) {
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if (shouldInsertLifetime)
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builder.create<LLVM::LifetimeEndOp>(
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allocaOp.getLoc(), arraySize.getValue().getLimitedValue(),
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allocaOp.getResult());
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}
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}
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}
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/// If `requestedAlignment` is higher than the alignment specified on `alloca`,
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/// realigns `alloca` if this does not exceed the natural stack alignment.
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/// Returns the post-alignment of `alloca`, whether it was realigned or not.
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static unsigned tryToEnforceAllocaAlignment(LLVM::AllocaOp alloca,
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unsigned requestedAlignment,
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DataLayout const &dataLayout) {
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unsigned allocaAlignment = alloca.getAlignment().value_or(1);
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if (requestedAlignment <= allocaAlignment)
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// No realignment necessary.
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return allocaAlignment;
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unsigned naturalStackAlignmentBits = dataLayout.getStackAlignment();
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// If the natural stack alignment is not specified, the data layout returns
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// zero. Optimistically allow realignment in this case.
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if (naturalStackAlignmentBits == 0 ||
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// If the requested alignment exceeds the natural stack alignment, this
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// will trigger a dynamic stack realignment, so we prefer to copy...
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8 * requestedAlignment <= naturalStackAlignmentBits ||
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// ...unless the alloca already triggers dynamic stack realignment. Then
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// we might as well further increase the alignment to avoid a copy.
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8 * allocaAlignment > naturalStackAlignmentBits) {
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alloca.setAlignment(requestedAlignment);
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allocaAlignment = requestedAlignment;
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}
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return allocaAlignment;
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}
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/// Tries to find and return the alignment of the pointer `value` by looking for
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/// an alignment attribute on the defining allocation op or function argument.
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/// If the found alignment is lower than `requestedAlignment`, tries to realign
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/// the pointer, then returns the resulting post-alignment, regardless of
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/// whether it was realigned or not. If no existing alignment attribute is
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/// found, returns 1 (i.e., assume that no alignment is guaranteed).
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static unsigned tryToEnforceAlignment(Value value, unsigned requestedAlignment,
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DataLayout const &dataLayout) {
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if (Operation *definingOp = value.getDefiningOp()) {
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if (auto alloca = dyn_cast<LLVM::AllocaOp>(definingOp))
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return tryToEnforceAllocaAlignment(alloca, requestedAlignment,
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dataLayout);
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if (auto addressOf = dyn_cast<LLVM::AddressOfOp>(definingOp))
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if (auto global = SymbolTable::lookupNearestSymbolFrom<LLVM::GlobalOp>(
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definingOp, addressOf.getGlobalNameAttr()))
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return global.getAlignment().value_or(1);
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// We don't currently handle this operation; assume no alignment.
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return 1;
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}
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// Since there is no defining op, this is a block argument. Probably this
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// comes directly from a function argument, so check that this is the case.
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Operation *parentOp = value.getParentBlock()->getParentOp();
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if (auto func = dyn_cast<LLVM::LLVMFuncOp>(parentOp)) {
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// Use the alignment attribute set for this argument in the parent function
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// if it has been set.
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auto blockArg = llvm::cast<BlockArgument>(value);
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if (Attribute alignAttr = func.getArgAttr(
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blockArg.getArgNumber(), LLVM::LLVMDialect::getAlignAttrName()))
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return cast<IntegerAttr>(alignAttr).getValue().getLimitedValue();
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}
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// We didn't find anything useful; assume no alignment.
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return 1;
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}
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/// Introduces a new alloca and copies the memory pointed to by `argument` to
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/// the address of the new alloca, then returns the value of the new alloca.
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static Value handleByValArgumentInit(OpBuilder &builder, Location loc,
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Value argument, Type elementType,
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unsigned elementTypeSize,
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unsigned targetAlignment) {
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// Allocate the new value on the stack.
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Value allocaOp;
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{
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// Since this is a static alloca, we can put it directly in the entry block,
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// so they can be absorbed into the prologue/epilogue at code generation.
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OpBuilder::InsertionGuard insertionGuard(builder);
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Block *entryBlock = &(*argument.getParentRegion()->begin());
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builder.setInsertionPointToStart(entryBlock);
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Value one = builder.create<LLVM::ConstantOp>(loc, builder.getI64Type(),
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builder.getI64IntegerAttr(1));
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allocaOp = builder.create<LLVM::AllocaOp>(
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loc, argument.getType(), elementType, one, targetAlignment);
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}
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// Copy the pointee to the newly allocated value.
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Value copySize = builder.create<LLVM::ConstantOp>(
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loc, builder.getI64Type(), builder.getI64IntegerAttr(elementTypeSize));
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builder.create<LLVM::MemcpyOp>(loc, allocaOp, argument, copySize,
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/*isVolatile=*/false);
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return allocaOp;
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}
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/// Handles a function argument marked with the byval attribute by introducing a
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/// memcpy or realigning the defining operation, if required either due to the
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/// pointee being writeable in the callee, and/or due to an alignment mismatch.
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/// `requestedAlignment` specifies the alignment set in the "align" argument
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/// attribute (or 1 if no align attribute was set).
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static Value handleByValArgument(OpBuilder &builder, Operation *callable,
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Value argument, Type elementType,
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unsigned requestedAlignment) {
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auto func = cast<LLVM::LLVMFuncOp>(callable);
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LLVM::MemoryEffectsAttr memoryEffects = func.getMemoryAttr();
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// If there is no memory effects attribute, assume that the function is
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// not read-only.
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bool isReadOnly = memoryEffects &&
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memoryEffects.getArgMem() != LLVM::ModRefInfo::ModRef &&
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memoryEffects.getArgMem() != LLVM::ModRefInfo::Mod;
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// Check if there's an alignment mismatch requiring us to copy.
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DataLayout dataLayout = DataLayout::closest(callable);
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unsigned minimumAlignment = dataLayout.getTypeABIAlignment(elementType);
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if (isReadOnly) {
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if (requestedAlignment <= minimumAlignment)
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return argument;
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unsigned currentAlignment =
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tryToEnforceAlignment(argument, requestedAlignment, dataLayout);
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if (currentAlignment >= requestedAlignment)
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return argument;
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}
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unsigned targetAlignment = std::max(requestedAlignment, minimumAlignment);
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return handleByValArgumentInit(builder, func.getLoc(), argument, elementType,
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dataLayout.getTypeSize(elementType),
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targetAlignment);
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}
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namespace {
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struct LLVMInlinerInterface : public DialectInlinerInterface {
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using DialectInlinerInterface::DialectInlinerInterface;
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LLVMInlinerInterface(Dialect *dialect)
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: DialectInlinerInterface(dialect),
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// Cache set of StringAttrs for fast lookup in `isLegalToInline`.
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disallowedFunctionAttrs({
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StringAttr::get(dialect->getContext(), "noduplicate"),
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StringAttr::get(dialect->getContext(), "noinline"),
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StringAttr::get(dialect->getContext(), "optnone"),
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StringAttr::get(dialect->getContext(), "presplitcoroutine"),
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StringAttr::get(dialect->getContext(), "returns_twice"),
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StringAttr::get(dialect->getContext(), "strictfp"),
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}) {}
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bool isLegalToInline(Operation *call, Operation *callable,
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bool wouldBeCloned) const final {
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if (!wouldBeCloned)
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return false;
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auto callOp = dyn_cast<LLVM::CallOp>(call);
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if (!callOp) {
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LLVM_DEBUG(llvm::dbgs()
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<< "Cannot inline: call is not an LLVM::CallOp\n");
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return false;
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}
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auto funcOp = dyn_cast<LLVM::LLVMFuncOp>(callable);
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if (!funcOp) {
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LLVM_DEBUG(llvm::dbgs()
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<< "Cannot inline: callable is not an LLVM::LLVMFuncOp\n");
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return false;
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}
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// TODO: Generate aliasing metadata from noalias argument/result attributes.
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if (auto attrs = funcOp.getArgAttrs()) {
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for (DictionaryAttr attrDict : attrs->getAsRange<DictionaryAttr>()) {
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if (attrDict.contains(LLVM::LLVMDialect::getInAllocaAttrName())) {
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LLVM_DEBUG(llvm::dbgs() << "Cannot inline " << funcOp.getSymName()
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<< ": inalloca arguments not supported\n");
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return false;
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}
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}
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}
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// TODO: Handle exceptions.
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if (funcOp.getPersonality()) {
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LLVM_DEBUG(llvm::dbgs() << "Cannot inline " << funcOp.getSymName()
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<< ": unhandled function personality\n");
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return false;
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}
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if (funcOp.getPassthrough()) {
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// TODO: Used attributes should not be passthrough.
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if (llvm::any_of(*funcOp.getPassthrough(), [&](Attribute attr) {
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auto stringAttr = dyn_cast<StringAttr>(attr);
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if (!stringAttr)
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return false;
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if (disallowedFunctionAttrs.contains(stringAttr)) {
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LLVM_DEBUG(llvm::dbgs()
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<< "Cannot inline " << funcOp.getSymName()
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<< ": found disallowed function attribute "
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<< stringAttr << "\n");
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return true;
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}
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return false;
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}))
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return false;
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}
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return true;
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}
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bool isLegalToInline(Region *, Region *, bool, IRMapping &) const final {
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return true;
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}
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/// Conservative allowlist of operations supported so far.
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bool isLegalToInline(Operation *op, Region *, bool, IRMapping &) const final {
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if (isPure(op))
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return true;
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// Some attributes on memory operations require handling during
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// inlining. Since this is not yet implemented, refuse to inline memory
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// operations that have any of these attributes.
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if (auto iface = dyn_cast<LLVM::AliasAnalysisOpInterface>(op)) {
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if (iface.getAliasScopesOrNull() || iface.getNoAliasScopesOrNull()) {
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LLVM_DEBUG(llvm::dbgs()
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<< "Cannot inline: unhandled alias analysis metadata\n");
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return false;
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}
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}
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if (auto iface = dyn_cast<LLVM::AccessGroupOpInterface>(op)) {
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if (iface.getAccessGroupsOrNull()) {
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LLVM_DEBUG(llvm::dbgs()
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<< "Cannot inline: unhandled access group metadata\n");
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return false;
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}
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}
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// clang-format off
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if (isa<LLVM::AllocaOp,
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LLVM::AssumeOp,
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LLVM::AtomicRMWOp,
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LLVM::AtomicCmpXchgOp,
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LLVM::CallOp,
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LLVM::DbgDeclareOp,
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LLVM::DbgValueOp,
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LLVM::FenceOp,
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LLVM::InlineAsmOp,
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LLVM::LifetimeEndOp,
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LLVM::LifetimeStartOp,
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LLVM::LoadOp,
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LLVM::MemcpyOp,
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LLVM::MemmoveOp,
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LLVM::MemsetOp,
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LLVM::StackRestoreOp,
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LLVM::StackSaveOp,
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LLVM::StoreOp,
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LLVM::UnreachableOp>(op))
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return true;
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// clang-format on
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LLVM_DEBUG(llvm::dbgs()
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<< "Cannot inline: unhandled side effecting operation \""
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<< op->getName() << "\"\n");
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return false;
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}
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/// Handle the given inlined return by replacing it with a branch. This
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/// overload is called when the inlined region has more than one block.
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void handleTerminator(Operation *op, Block *newDest) const final {
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// Only return needs to be handled here.
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auto returnOp = dyn_cast<LLVM::ReturnOp>(op);
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if (!returnOp)
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return;
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// Replace the return with a branch to the dest.
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OpBuilder builder(op);
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builder.create<LLVM::BrOp>(op->getLoc(), returnOp.getOperands(), newDest);
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op->erase();
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}
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/// Handle the given inlined return by replacing the uses of the call with the
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/// operands of the return. This overload is called when the inlined region
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/// only contains one block.
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void handleTerminator(Operation *op,
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ArrayRef<Value> valuesToRepl) const final {
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// Return will be the only terminator present.
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auto returnOp = cast<LLVM::ReturnOp>(op);
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// Replace the values directly with the return operands.
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assert(returnOp.getNumOperands() == valuesToRepl.size());
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for (const auto &[dst, src] :
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llvm::zip(valuesToRepl, returnOp.getOperands()))
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dst.replaceAllUsesWith(src);
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}
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Value handleArgument(OpBuilder &builder, Operation *call, Operation *callable,
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Value argument,
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DictionaryAttr argumentAttrs) const final {
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if (std::optional<NamedAttribute> attr =
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argumentAttrs.getNamed(LLVM::LLVMDialect::getByValAttrName())) {
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Type elementType = cast<TypeAttr>(attr->getValue()).getValue();
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unsigned requestedAlignment = 1;
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if (std::optional<NamedAttribute> alignAttr =
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argumentAttrs.getNamed(LLVM::LLVMDialect::getAlignAttrName())) {
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requestedAlignment = cast<IntegerAttr>(alignAttr->getValue())
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.getValue()
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.getLimitedValue();
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}
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return handleByValArgument(builder, callable, argument, elementType,
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requestedAlignment);
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}
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return argument;
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}
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void processInlinedCallBlocks(
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Operation *call,
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iterator_range<Region::iterator> inlinedBlocks) const override {
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handleInlinedAllocas(call, inlinedBlocks);
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}
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// Keeping this (immutable) state on the interface allows us to look up
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// StringAttrs instead of looking up strings, since StringAttrs are bound to
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// the current context and thus cannot be initialized as static fields.
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const DenseSet<StringAttr> disallowedFunctionAttrs;
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};
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} // end anonymous namespace
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void LLVM::detail::addLLVMInlinerInterface(LLVM::LLVMDialect *dialect) {
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dialect->addInterfaces<LLVMInlinerInterface>();
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}
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