8e70273509
As part of the "RemoveDIs" project, BasicBlock::iterator now carries a debug-info bit that's needed when getFirstNonPHI and similar feed into instruction insertion positions. Call-sites where that's necessary were updated a year ago; but to ensure some type safety however, we'd like to have all calls to moveBefore use iterators. This patch adds a (guaranteed dereferenceable) iterator-taking moveBefore, and changes a bunch of call-sites where it's obviously safe to change to use it by just calling getIterator() on an instruction pointer. A follow-up patch will contain less-obviously-safe changes. We'll eventually deprecate and remove the instruction-pointer insertBefore, but not before adding concise documentation of what considerations are needed (very few).
93 lines
3.1 KiB
C++
93 lines
3.1 KiB
C++
//===-- BPFASpaceCastSimplifyPass.cpp - BPF addrspacecast simplications --===//
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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 "BPF.h"
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#include <optional>
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#define DEBUG_TYPE "bpf-aspace-simplify"
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using namespace llvm;
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namespace {
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struct CastGEPCast {
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AddrSpaceCastInst *OuterCast;
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// Match chain of instructions:
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// %inner = addrspacecast N->M
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// %gep = getelementptr %inner, ...
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// %outer = addrspacecast M->N %gep
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// Where I is %outer.
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static std::optional<CastGEPCast> match(Value *I) {
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auto *OuterCast = dyn_cast<AddrSpaceCastInst>(I);
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if (!OuterCast)
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return std::nullopt;
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auto *GEP = dyn_cast<GetElementPtrInst>(OuterCast->getPointerOperand());
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if (!GEP)
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return std::nullopt;
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auto *InnerCast = dyn_cast<AddrSpaceCastInst>(GEP->getPointerOperand());
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if (!InnerCast)
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return std::nullopt;
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if (InnerCast->getSrcAddressSpace() != OuterCast->getDestAddressSpace())
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return std::nullopt;
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if (InnerCast->getDestAddressSpace() != OuterCast->getSrcAddressSpace())
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return std::nullopt;
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return CastGEPCast{OuterCast};
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}
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static PointerType *changeAddressSpace(PointerType *Ty, unsigned AS) {
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return Ty->get(Ty->getContext(), AS);
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}
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// Assuming match(this->OuterCast) is true, convert:
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// (addrspacecast M->N (getelementptr (addrspacecast N->M ptr) ...))
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// To:
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// (getelementptr ptr ...)
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GetElementPtrInst *rewrite() {
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auto *GEP = cast<GetElementPtrInst>(OuterCast->getPointerOperand());
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auto *InnerCast = cast<AddrSpaceCastInst>(GEP->getPointerOperand());
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unsigned AS = OuterCast->getDestAddressSpace();
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auto *NewGEP = cast<GetElementPtrInst>(GEP->clone());
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NewGEP->setName(GEP->getName());
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NewGEP->insertAfter(OuterCast->getIterator());
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NewGEP->setOperand(0, InnerCast->getPointerOperand());
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auto *GEPTy = cast<PointerType>(GEP->getType());
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NewGEP->mutateType(changeAddressSpace(GEPTy, AS));
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OuterCast->replaceAllUsesWith(NewGEP);
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OuterCast->eraseFromParent();
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if (GEP->use_empty())
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GEP->eraseFromParent();
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if (InnerCast->use_empty())
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InnerCast->eraseFromParent();
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return NewGEP;
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}
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};
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} // anonymous namespace
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PreservedAnalyses BPFASpaceCastSimplifyPass::run(Function &F,
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FunctionAnalysisManager &AM) {
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SmallVector<CastGEPCast, 16> WorkList;
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bool Changed = false;
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for (BasicBlock &BB : F) {
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for (Instruction &I : BB)
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if (auto It = CastGEPCast::match(&I))
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WorkList.push_back(It.value());
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Changed |= !WorkList.empty();
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while (!WorkList.empty()) {
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CastGEPCast InsnChain = WorkList.pop_back_val();
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GetElementPtrInst *NewGEP = InsnChain.rewrite();
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for (User *U : NewGEP->users())
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if (auto It = CastGEPCast::match(U))
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WorkList.push_back(It.value());
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}
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}
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return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
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}
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