llvm/llvm/lib/Target/BPF/BPFAdjustOpt.cpp

//===---------------- BPFAdjustOpt.cpp - Adjust Optimization --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Adjust optimization to make the code more kernel verifier friendly.
//
//===----------------------------------------------------------------------===//

#include "BPF.h"
#include "BPFCORE.h"
#include "BPFTargetMachine.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicsBPF.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"

#define DEBUG_TYPE …

usingnamespacellvm;
usingnamespacellvm::PatternMatch;

static cl::opt<bool>
    DisableBPFserializeICMP("bpf-disable-serialize-icmp", cl::Hidden,
                            cl::desc("BPF: Disable Serializing ICMP insns."),
                            cl::init(false));

static cl::opt<bool> DisableBPFavoidSpeculation(
    "bpf-disable-avoid-speculation", cl::Hidden,
    cl::desc("BPF: Disable Avoiding Speculative Code Motion."),
    cl::init(false));

namespace {
class BPFAdjustOptImpl { … };

} // End anonymous namespace

bool BPFAdjustOptImpl::run() { … }

// Commit acabad9ff6bf ("[InstCombine] try to canonicalize icmp with
// trunc op into mask and cmp") added a transformation to
// convert "(conv)a < power_2_const" to "a & <const>" in certain
// cases and bpf kernel verifier has to handle the resulted code
// conservatively and this may reject otherwise legitimate program.
// Here, we change related icmp code to a builtin which will
// be restored to original icmp code later to prevent that
// InstCombine transformatin.
bool BPFAdjustOptImpl::adjustICmpToBuiltin() { … }

bool BPFAdjustOptImpl::insertPassThrough() { … }

// To avoid combining conditionals in the same basic block by
// instrcombine optimization.
bool BPFAdjustOptImpl::serializeICMPInBB(Instruction &I) { … }

// To avoid combining conditionals in the same basic block by
// instrcombine optimization.
bool BPFAdjustOptImpl::serializeICMPCrossBB(BasicBlock &BB) { … }

// To avoid speculative hoisting certain computations out of
// a basic block.
bool BPFAdjustOptImpl::avoidSpeculation(Instruction &I) { … }

void BPFAdjustOptImpl::adjustBasicBlock(BasicBlock &BB) { … }

void BPFAdjustOptImpl::adjustInst(Instruction &I) { … }

PreservedAnalyses BPFAdjustOptPass::run(Module &M, ModuleAnalysisManager &AM) { … }