/*
* Copyright 2016 laf-intel
* extended for floating point by Heiko Eißfeldt
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <list>
#include <string>
#include <fstream>
#include <sys/time.h>
#include "llvm/Config/llvm-config.h"
#include "llvm/Pass.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/IRBuilder.h"
#if LLVM_VERSION_MAJOR > 3 || \
(LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR > 4)
#include "llvm/IR/Verifier.h"
#include "llvm/IR/DebugInfo.h"
#else
#include "llvm/Analysis/Verifier.h"
#include "llvm/DebugInfo.h"
#define nullptr 0
#endif
using namespace llvm;
#include "afl-llvm-common.h"
// uncomment this toggle function verification at each step. horribly slow, but
// helps to pinpoint a potential problem in the splitting code.
//#define VERIFY_TOO_MUCH 1
namespace {
class SplitComparesTransform : public ModulePass {
public:
static char ID;
SplitComparesTransform() : ModulePass(ID), enableFPSplit(0) {
initInstrumentList();
}
bool runOnModule(Module &M) override;
#if LLVM_VERSION_MAJOR >= 4
StringRef getPassName() const override {
#else
const char *getPassName() const override {
#endif
return "AFL_SplitComparesTransform";
}
private:
int enableFPSplit;
unsigned target_bitwidth = 8;
size_t count = 0;
size_t splitFPCompares(Module &M);
bool simplifyFPCompares(Module &M);
size_t nextPowerOfTwo(size_t in);
using CmpWorklist = SmallVector<CmpInst *, 8>;
/// simplify the comparison and then split the comparison until the
/// target_bitwidth is reached.
bool simplifyAndSplit(CmpInst *I, Module &M);
/// simplify a non-strict comparison (e.g., less than or equals)
bool simplifyOrEqualsCompare(CmpInst *IcmpInst, Module &M,
CmpWorklist &worklist);
/// simplify a signed comparison (signed less or greater than)
bool simplifySignedCompare(CmpInst *IcmpInst, Module &M,
CmpWorklist &worklist);
/// splits an icmp into nested icmps recursivly until target_bitwidth is
/// reached
bool splitCompare(CmpInst *I, Module &M, CmpWorklist &worklist);
/// print an error to llvm's errs stream, but only if not ordered to be quiet
void reportError(const StringRef msg, Instruction *I, Module &M) {
if (!be_quiet) {
errs() << "[AFL++ SplitComparesTransform] ERROR: " << msg << "\n";
if (debug) {
if (I) {
errs() << "Instruction = " << *I << "\n";
if (auto BB = I->getParent()) {
if (auto F = BB->getParent()) {
if (F->hasName()) {
errs() << "|-> in function " << F->getName() << " ";
}
}
}
}
auto n = M.getName();
if (n.size() > 0) { errs() << "in module " << n << "\n"; }
}
}
}
bool isSupportedBitWidth(unsigned bitw) {
// IDK whether the icmp code works on other bitwidths. I guess not? So we
// try to avoid dealing with other weird icmp's that llvm might use (looking
// at you `icmp i0`).
switch (bitw) {
case 8:
case 16:
case 32:
case 64:
case 128:
case 256:
return true;
default:
return false;
}
}
};
} // namespace
char SplitComparesTransform::ID = 0;
/// This function splits FCMP instructions with xGE or xLE predicates into two
/// FCMP instructions with predicate xGT or xLT and EQ
bool SplitComparesTransform::simplifyFPCompares(Module &M) {
LLVMContext & C = M.getContext();
std::vector<Instruction *> fcomps;
IntegerType * Int1Ty = IntegerType::getInt1Ty(C);
/* iterate over all functions, bbs and instruction and add
* all integer comparisons with >= and <= predicates to the icomps vector */
for (auto &F : M) {
if (!isInInstrumentList(&F)) continue;
for (auto &BB : F) {
for (auto &IN : BB) {
CmpInst *selectcmpInst = nullptr;
if ((selectcmpInst = dyn_cast<CmpInst>(&IN))) {
if (enableFPSplit &&
(selectcmpInst->getPredicate() == CmpInst::FCMP_OGE ||
selectcmpInst->getPredicate() == CmpInst::FCMP_UGE ||
selectcmpInst->getPredicate() == CmpInst::FCMP_OLE ||
selectcmpInst->getPredicate() == CmpInst::FCMP_ULE)) {
auto op0 = selectcmpInst->getOperand(0);
auto op1 = selectcmpInst->getOperand(1);
Type *TyOp0 = op0->getType();
Type *TyOp1 = op1->getType();
/* this is probably not needed but we do it anyway */
if (TyOp0 != TyOp1) { continue; }
if (TyOp0->isArrayTy() || TyOp0->isVectorTy()) { continue; }
fcomps.push_back(selectcmpInst);
}
}
}
}
}
if (!fcomps.size()) { return false; }
/* transform for floating point */
for (auto &FcmpInst : fcomps) {
BasicBlock *bb = FcmpInst->getParent();
auto op0 = FcmpInst->getOperand(0);
auto op1 = FcmpInst->getOperand(1);
/* find out what the new predicate is going to be */
auto cmp_inst = dyn_cast<CmpInst>(FcmpInst);
if (!cmp_inst) { continue; }
auto pred = cmp_inst->getPredicate();
CmpInst::Predicate new_pred;
switch (pred) {
case CmpInst::FCMP_UGE:
new_pred = CmpInst::FCMP_UGT;
break;
case CmpInst::FCMP_OGE:
new_pred = CmpInst::FCMP_OGT;
break;
case CmpInst::FCMP_ULE:
new_pred = CmpInst::FCMP_ULT;
break;
case CmpInst::FCMP_OLE:
new_pred = CmpInst::FCMP_OLT;
break;
default: // keep the compiler happy
continue;
}
/* split before the fcmp instruction */
BasicBlock *end_bb = bb->splitBasicBlock(BasicBlock::iterator(FcmpInst));
/* the old bb now contains a unconditional jump to the new one (end_bb)
* we need to delete it later */
/* create the FCMP instruction with new_pred and add it to the old basic
* block bb it is now at the position where the old FcmpInst was */
Instruction *fcmp_np;
fcmp_np = CmpInst::Create(Instruction::FCmp, new_pred, op0, op1);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()),
fcmp_np);
/* create a new basic block which holds the new EQ fcmp */
Instruction *fcmp_eq;
/* insert middle_bb before end_bb */
BasicBlock *middle_bb =
BasicBlock::Create(C, "injected", end_bb->getParent(), end_bb);
fcmp_eq = CmpInst::Create(Instruction::FCmp, CmpInst::FCMP_OEQ, op0, op1);
middle_bb->getInstList().push_back(fcmp_eq);
/* add an unconditional branch to the end of middle_bb with destination
* end_bb */
BranchInst::Create(end_bb, middle_bb);
/* replace the uncond branch with a conditional one, which depends on the
* new_pred fcmp. True goes to end, false to the middle (injected) bb */
auto term = bb->getTerminator();
BranchInst::Create(end_bb, middle_bb, fcmp_np, bb);
term->eraseFromParent();
/* replace the old FcmpInst (which is the first inst in end_bb) with a PHI
* inst to wire up the loose ends */
PHINode *PN = PHINode::Create(Int1Ty, 2, "");
/* the first result depends on the outcome of fcmp_eq */
PN->addIncoming(fcmp_eq, middle_bb);
/* if the source was the original bb we know that the fcmp_np yielded true
* hence we can hardcode this value */
PN->addIncoming(ConstantInt::get(Int1Ty, 1), bb);
/* replace the old FcmpInst with our new and shiny PHI inst */
BasicBlock::iterator ii(FcmpInst);
ReplaceInstWithInst(FcmpInst->getParent()->getInstList(), ii, PN);
}
return true;
}
/// This function splits ICMP instructions with xGE or xLE predicates into two
/// ICMP instructions with predicate xGT or xLT and EQ
bool SplitComparesTransform::simplifyOrEqualsCompare(CmpInst * IcmpInst,
Module & M,
CmpWorklist &worklist) {
LLVMContext &C = M.getContext();
IntegerType *Int1Ty = IntegerType::getInt1Ty(C);
/* find out what the new predicate is going to be */
auto cmp_inst = dyn_cast<CmpInst>(IcmpInst);
if (!cmp_inst) { return false; }
BasicBlock *bb = IcmpInst->getParent();
auto op0 = IcmpInst->getOperand(0);
auto op1 = IcmpInst->getOperand(1);
CmpInst::Predicate pred = cmp_inst->getPredicate();
CmpInst::Predicate new_pred;
switch (pred) {
case CmpInst::ICMP_UGE:
new_pred = CmpInst::ICMP_UGT;
break;
case CmpInst::ICMP_SGE:
new_pred = CmpInst::ICMP_SGT;
break;
case CmpInst::ICMP_ULE:
new_pred = CmpInst::ICMP_ULT;
break;
case CmpInst::ICMP_SLE:
new_pred = CmpInst::ICMP_SLT;
break;
default: // keep the compiler happy
return false;
}
/* split before the icmp instruction */
BasicBlock *end_bb = bb->splitBasicBlock(BasicBlock::iterator(IcmpInst));
/* the old bb now contains a unconditional jump to the new one (end_bb)
* we need to delete it later */
/* create the ICMP instruction with new_pred and add it to the old basic
* block bb it is now at the position where the old IcmpInst was */
CmpInst *icmp_np = CmpInst::Create(Instruction::ICmp, new_pred, op0, op1);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), icmp_np);
/* create a new basic block which holds the new EQ icmp */
CmpInst *icmp_eq;
/* insert middle_bb before end_bb */
BasicBlock *middle_bb =
BasicBlock::Create(C, "injected", end_bb->getParent(), end_bb);
icmp_eq = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, op0, op1);
middle_bb->getInstList().push_back(icmp_eq);
/* add an unconditional branch to the end of middle_bb with destination
* end_bb */
BranchInst::Create(end_bb, middle_bb);
/* replace the uncond branch with a conditional one, which depends on the
* new_pred icmp. True goes to end, false to the middle (injected) bb */
auto term = bb->getTerminator();
BranchInst::Create(end_bb, middle_bb, icmp_np, bb);
term->eraseFromParent();
/* replace the old IcmpInst (which is the first inst in end_bb) with a PHI
* inst to wire up the loose ends */
PHINode *PN = PHINode::Create(Int1Ty, 2, "");
/* the first result depends on the outcome of icmp_eq */
PN->addIncoming(icmp_eq, middle_bb);
/* if the source was the original bb we know that the icmp_np yielded true
* hence we can hardcode this value */
PN->addIncoming(ConstantInt::get(Int1Ty, 1), bb);
/* replace the old IcmpInst with our new and shiny PHI inst */
BasicBlock::iterator ii(IcmpInst);
ReplaceInstWithInst(IcmpInst->getParent()->getInstList(), ii, PN);
worklist.push_back(icmp_np);
worklist.push_back(icmp_eq);
return true;
}
/// Simplify a signed comparison operator by splitting it into a unsigned and
/// bit comparison. add all resulting comparisons to
/// the worklist passed as a reference.
bool SplitComparesTransform::simplifySignedCompare(CmpInst *IcmpInst, Module &M,
CmpWorklist &worklist) {
LLVMContext &C = M.getContext();
IntegerType *Int1Ty = IntegerType::getInt1Ty(C);
BasicBlock *bb = IcmpInst->getParent();
auto op0 = IcmpInst->getOperand(0);
auto op1 = IcmpInst->getOperand(1);
IntegerType *intTyOp0 = dyn_cast<IntegerType>(op0->getType());
if (!intTyOp0) { return false; }
unsigned bitw = intTyOp0->getBitWidth();
IntegerType *IntType = IntegerType::get(C, bitw);
/* get the new predicate */
auto cmp_inst = dyn_cast<CmpInst>(IcmpInst);
if (!cmp_inst) { return false; }
auto pred = cmp_inst->getPredicate();
CmpInst::Predicate new_pred;
if (pred == CmpInst::ICMP_SGT) {
new_pred = CmpInst::ICMP_UGT;
} else {
new_pred = CmpInst::ICMP_ULT;
}
BasicBlock *end_bb = bb->splitBasicBlock(BasicBlock::iterator(IcmpInst));
/* create a 1 bit compare for the sign bit. to do this shift and trunc
* the original operands so only the first bit remains.*/
Value *s_op0, *t_op0, *s_op1, *t_op1, *icmp_sign_bit;
IRBuilder<> IRB(bb->getTerminator());
s_op0 = IRB.CreateLShr(op0, ConstantInt::get(IntType, bitw - 1));
t_op0 = IRB.CreateTruncOrBitCast(s_op0, Int1Ty);
s_op1 = IRB.CreateLShr(op1, ConstantInt::get(IntType, bitw - 1));
t_op1 = IRB.CreateTruncOrBitCast(s_op1, Int1Ty);
/* compare of the sign bits */
icmp_sign_bit = IRB.CreateICmp(CmpInst::ICMP_EQ, t_op0, t_op1);
/* create a new basic block which is executed if the signedness bit is
* different */
CmpInst * icmp_inv_sig_cmp;
BasicBlock *sign_bb =
BasicBlock::Create(C, "sign", end_bb->getParent(), end_bb);
if (pred == CmpInst::ICMP_SGT) {
/* if we check for > and the op0 positive and op1 negative then the final
* result is true. if op0 negative and op1 pos, the cmp must result
* in false
*/
icmp_inv_sig_cmp =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULT, t_op0, t_op1);
} else {
/* just the inverse of the above statement */
icmp_inv_sig_cmp =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_UGT, t_op0, t_op1);
}
sign_bb->getInstList().push_back(icmp_inv_sig_cmp);
BranchInst::Create(end_bb, sign_bb);
/* create a new bb which is executed if signedness is equal */
CmpInst * icmp_usign_cmp;
BasicBlock *middle_bb =
BasicBlock::Create(C, "injected", end_bb->getParent(), end_bb);
/* we can do a normal unsigned compare now */
icmp_usign_cmp = CmpInst::Create(Instruction::ICmp, new_pred, op0, op1);
middle_bb->getInstList().push_back(icmp_usign_cmp);
BranchInst::Create(end_bb, middle_bb);
auto term = bb->getTerminator();
/* if the sign is eq do a normal unsigned cmp, else we have to check the
* signedness bit */
BranchInst::Create(middle_bb, sign_bb, icmp_sign_bit, bb);
term->eraseFromParent();
PHINode *PN = PHINode::Create(Int1Ty, 2, "");
PN->addIncoming(icmp_usign_cmp, middle_bb);
PN->addIncoming(icmp_inv_sig_cmp, sign_bb);
BasicBlock::iterator ii(IcmpInst);
ReplaceInstWithInst(IcmpInst->getParent()->getInstList(), ii, PN);
// save for later
worklist.push_back(icmp_usign_cmp);
// signed comparisons are not supported by the splitting code, so we must not
// add it to the worklist.
// worklist.push_back(icmp_inv_sig_cmp);
return true;
}
bool SplitComparesTransform::splitCompare(CmpInst *cmp_inst, Module &M,
CmpWorklist &worklist) {
auto pred = cmp_inst->getPredicate();
switch (pred) {
case CmpInst::ICMP_EQ:
case CmpInst::ICMP_NE:
case CmpInst::ICMP_UGT:
case CmpInst::ICMP_ULT:
break;
default:
// unsupported predicate!
return false;
}
auto op0 = cmp_inst->getOperand(0);
auto op1 = cmp_inst->getOperand(1);
// get bitwidth by checking the bitwidth of the first operator
IntegerType *intTyOp0 = dyn_cast<IntegerType>(op0->getType());
if (!intTyOp0) {
// not an integer type
return false;
}
unsigned bitw = intTyOp0->getBitWidth();
if (bitw == target_bitwidth) {
// already the target bitwidth so we have to do nothing here.
return true;
}
LLVMContext &C = M.getContext();
IntegerType *Int1Ty = IntegerType::getInt1Ty(C);
BasicBlock * bb = cmp_inst->getParent();
IntegerType *OldIntType = IntegerType::get(C, bitw);
IntegerType *NewIntType = IntegerType::get(C, bitw / 2);
BasicBlock * end_bb = bb->splitBasicBlock(BasicBlock::iterator(cmp_inst));
CmpInst * icmp_high, *icmp_low;
/* create the comparison of the top halves of the original operands */
Value *s_op0, *op0_high, *s_op1, *op1_high;
IRBuilder<> IRB(bb->getTerminator());
s_op0 = IRB.CreateBinOp(Instruction::LShr, op0,
ConstantInt::get(OldIntType, bitw / 2));
op0_high = IRB.CreateTruncOrBitCast(s_op0, NewIntType);
s_op1 = IRB.CreateBinOp(Instruction::LShr, op1,
ConstantInt::get(OldIntType, bitw / 2));
op1_high = IRB.CreateTruncOrBitCast(s_op1, NewIntType);
icmp_high = cast<CmpInst>(IRB.CreateICmp(pred, op0_high, op1_high));
PHINode *PN = nullptr;
/* now we have to destinguish between == != and > < */
switch (pred) {
case CmpInst::ICMP_EQ:
case CmpInst::ICMP_NE: {
/* transformation for == and != icmps */
/* create a compare for the lower half of the original operands */
BasicBlock *cmp_low_bb =
BasicBlock::Create(C, "" /*"injected"*/, end_bb->getParent(), end_bb);
Value * op0_low, *op1_low;
IRBuilder<> Builder(cmp_low_bb);
op0_low = Builder.CreateTrunc(op0, NewIntType);
op1_low = Builder.CreateTrunc(op1, NewIntType);
icmp_low = cast<CmpInst>(Builder.CreateICmp(pred, op0_low, op1_low));
BranchInst::Create(end_bb, cmp_low_bb);
/* dependent on the cmp of the high parts go to the end or go on with
* the comparison */
auto term = bb->getTerminator();
if (pred == CmpInst::ICMP_EQ) {
BranchInst::Create(cmp_low_bb, end_bb, icmp_high, bb);
} else {
// CmpInst::ICMP_NE
BranchInst::Create(end_bb, cmp_low_bb, icmp_high, bb);
}
term->eraseFromParent();
/* create the PHI and connect the edges accordingly */
PN = PHINode::Create(Int1Ty, 2, "");
PN->addIncoming(icmp_low, cmp_low_bb);
Value *val = nullptr;
if (pred == CmpInst::ICMP_EQ) {
val = ConstantInt::get(Int1Ty, 0);
} else {
/* CmpInst::ICMP_NE */
val = ConstantInt::get(Int1Ty, 1);
}
PN->addIncoming(val, icmp_high->getParent());
break;
}
case CmpInst::ICMP_UGT:
case CmpInst::ICMP_ULT: {
/* transformations for < and > */
/* create a basic block which checks for the inverse predicate.
* if this is true we can go to the end if not we have to go to the
* bb which checks the lower half of the operands */
Instruction *op0_low, *op1_low;
CmpInst * icmp_inv_cmp = nullptr;
BasicBlock * inv_cmp_bb =
BasicBlock::Create(C, "inv_cmp", end_bb->getParent(), end_bb);
if (pred == CmpInst::ICMP_UGT) {
icmp_inv_cmp = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULT,
op0_high, op1_high);
} else {
icmp_inv_cmp = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_UGT,
op0_high, op1_high);
}
inv_cmp_bb->getInstList().push_back(icmp_inv_cmp);
worklist.push_back(icmp_inv_cmp);
auto term = bb->getTerminator();
term->eraseFromParent();
BranchInst::Create(end_bb, inv_cmp_bb, icmp_high, bb);
/* create a bb which handles the cmp of the lower halves */
BasicBlock *cmp_low_bb =
BasicBlock::Create(C, "" /*"injected"*/, end_bb->getParent(), end_bb);
op0_low = new TruncInst(op0, NewIntType);
cmp_low_bb->getInstList().push_back(op0_low);
op1_low = new TruncInst(op1, NewIntType);
cmp_low_bb->getInstList().push_back(op1_low);
icmp_low = CmpInst::Create(Instruction::ICmp, pred, op0_low, op1_low);
cmp_low_bb->getInstList().push_back(icmp_low);
BranchInst::Create(end_bb, cmp_low_bb);
BranchInst::Create(end_bb, cmp_low_bb, icmp_inv_cmp, inv_cmp_bb);
PN = PHINode::Create(Int1Ty, 3);
PN->addIncoming(icmp_low, cmp_low_bb);
PN->addIncoming(ConstantInt::get(Int1Ty, 1), bb);
PN->addIncoming(ConstantInt::get(Int1Ty, 0), inv_cmp_bb);
break;
}
default:
return false;
}
BasicBlock::iterator ii(cmp_inst);
ReplaceInstWithInst(cmp_inst->getParent()->getInstList(), ii, PN);
// We split the comparison into low and high. If this isn't our target
// bitwidth we recursivly split the low and high parts again until we have
// target bitwidth.
if ((bitw / 2) > target_bitwidth) {
worklist.push_back(icmp_high);
worklist.push_back(icmp_low);
}
return true;
}
bool SplitComparesTransform::simplifyAndSplit(CmpInst *I, Module &M) {
CmpWorklist worklist;
auto op0 = I->getOperand(0);
auto op1 = I->getOperand(1);
if (!op0 || !op1) { return false; }
auto op0Ty = dyn_cast<IntegerType>(op0->getType());
if (!op0Ty || !isa<IntegerType>(op1->getType())) { return true; }
unsigned bitw = op0Ty->getBitWidth();
#ifdef VERIFY_TOO_MUCH
auto F = I->getParent()->getParent();
#endif
// we run the comparison simplification on all compares regardless of their
// bitwidth.
if (I->getPredicate() == CmpInst::ICMP_UGE ||
I->getPredicate() == CmpInst::ICMP_SGE ||
I->getPredicate() == CmpInst::ICMP_ULE ||
I->getPredicate() == CmpInst::ICMP_SLE) {
if (!simplifyOrEqualsCompare(I, M, worklist)) {
reportError(
"Failed to simplify inequality or equals comparison "
"(UGE,SGE,ULE,SLE)",
I, M);
}
} else if (I->getPredicate() == CmpInst::ICMP_SGT ||
I->getPredicate() == CmpInst::ICMP_SLT) {
if (!simplifySignedCompare(I, M, worklist)) {
reportError("Failed to simplify signed comparison (SGT,SLT)", I, M);
}
}
#ifdef VERIFY_TOO_MUCH
if (verifyFunction(*F, &errs())) {
reportError("simpliyfing compare lead to broken function", nullptr, M);
}
#endif
// the simplification methods replace the original CmpInst and push the
// resulting new CmpInst into the worklist. If the worklist is empty then
// we only have to split the original CmpInst.
if (worklist.size() == 0) { worklist.push_back(I); }
while (!worklist.empty()) {
CmpInst *cmp = worklist.pop_back_val();
// we split the simplified compares into comparisons with smaller bitwidths
// if they are larger than our target_bitwidth.
if (bitw > target_bitwidth) {
if (!splitCompare(cmp, M, worklist)) {
reportError("Failed to split comparison", cmp, M);
}
#ifdef VERIFY_TOO_MUCH
if (verifyFunction(*F, &errs())) {
reportError("splitting compare lead to broken function", nullptr, M);
}
#endif
}
}
count++;
return true;
}
size_t SplitComparesTransform::nextPowerOfTwo(size_t in) {
--in;
in |= in >> 1;
in |= in >> 2;
in |= in >> 4;
// in |= in >> 8;
// in |= in >> 16;
return in + 1;
}
/* splits fcmps into two nested fcmps with sign compare and the rest */
size_t SplitComparesTransform::splitFPCompares(Module &M) {
size_t count = 0;
LLVMContext &C = M.getContext();
#if LLVM_VERSION_MAJOR > 3 || \
(LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR > 7)
const DataLayout &dl = M.getDataLayout();
/* define unions with floating point and (sign, exponent, mantissa) triples
*/
if (dl.isLittleEndian()) {
} else if (dl.isBigEndian()) {
} else {
return count;
}
#endif
std::vector<CmpInst *> fcomps;
/* get all EQ, NE, GT, and LT fcmps. if the other two
* functions were executed only these four predicates should exist */
for (auto &F : M) {
if (!isInInstrumentList(&F)) continue;
for (auto &BB : F) {
for (auto &IN : BB) {
CmpInst *selectcmpInst = nullptr;
if ((selectcmpInst = dyn_cast<CmpInst>(&IN))) {
if (selectcmpInst->getPredicate() == CmpInst::FCMP_OEQ ||
selectcmpInst->getPredicate() == CmpInst::FCMP_UEQ ||
selectcmpInst->getPredicate() == CmpInst::FCMP_ONE ||
selectcmpInst->getPredicate() == CmpInst::FCMP_UNE ||
selectcmpInst->getPredicate() == CmpInst::FCMP_UGT ||
selectcmpInst->getPredicate() == CmpInst::FCMP_OGT ||
selectcmpInst->getPredicate() == CmpInst::FCMP_ULT ||
selectcmpInst->getPredicate() == CmpInst::FCMP_OLT) {
auto op0 = selectcmpInst->getOperand(0);
auto op1 = selectcmpInst->getOperand(1);
Type *TyOp0 = op0->getType();
Type *TyOp1 = op1->getType();
if (TyOp0 != TyOp1) { continue; }
if (TyOp0->isArrayTy() || TyOp0->isVectorTy()) { continue; }
fcomps.push_back(selectcmpInst);
}
}
}
}
}
if (!fcomps.size()) { return count; }
IntegerType *Int1Ty = IntegerType::getInt1Ty(C);
for (auto &FcmpInst : fcomps) {
BasicBlock *bb = FcmpInst->getParent();
auto op0 = FcmpInst->getOperand(0);
auto op1 = FcmpInst->getOperand(1);
unsigned op_size;
op_size = op0->getType()->getPrimitiveSizeInBits();
if (op_size != op1->getType()->getPrimitiveSizeInBits()) { continue; }
const unsigned int sizeInBits = op0->getType()->getPrimitiveSizeInBits();
// BUG FIXME TODO: u64 does not work for > 64 bit ... e.g. 80 and 128 bit
if (sizeInBits > 64) { continue; }
const unsigned int precision = sizeInBits == 32 ? 24
: sizeInBits == 64 ? 53
: sizeInBits == 128 ? 113
: sizeInBits == 16 ? 11
: sizeInBits == 80 ? 65
: sizeInBits - 8;
const unsigned shiftR_exponent = precision - 1;
const unsigned long long mask_fraction =
(1ULL << (shiftR_exponent - 1)) | ((1ULL << (shiftR_exponent - 1)) - 1);
const unsigned long long mask_exponent =
(1ULL << (sizeInBits - precision)) - 1;
// round up sizes to the next power of two
// this should help with integer compare splitting
size_t exTySizeBytes = ((sizeInBits - precision + 7) >> 3);
size_t frTySizeBytes = ((precision - 1ULL + 7) >> 3);
IntegerType *IntExponentTy =
IntegerType::get(C, nextPowerOfTwo(exTySizeBytes) << 3);
IntegerType *IntFractionTy =
IntegerType::get(C, nextPowerOfTwo(frTySizeBytes) << 3);
// errs() << "Fractions: IntFractionTy size " <<
// IntFractionTy->getPrimitiveSizeInBits() << ", op_size " << op_size <<
// ", mask " << mask_fraction <<
// ", precision " << precision << "\n";
BasicBlock *end_bb = bb->splitBasicBlock(BasicBlock::iterator(FcmpInst));
/* create the integers from floats directly */
Instruction *b_op0, *b_op1;
b_op0 = CastInst::Create(Instruction::BitCast, op0,
IntegerType::get(C, op_size));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), b_op0);
b_op1 = CastInst::Create(Instruction::BitCast, op1,
IntegerType::get(C, op_size));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), b_op1);
/* isolate signs of value of floating point type */
/* create a 1 bit compare for the sign bit. to do this shift and trunc
* the original operands so only the first bit remains.*/
Instruction *s_s0, *t_s0, *s_s1, *t_s1, *icmp_sign_bit;
s_s0 =
BinaryOperator::Create(Instruction::LShr, b_op0,
ConstantInt::get(b_op0->getType(), op_size - 1));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), s_s0);
t_s0 = new TruncInst(s_s0, Int1Ty);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), t_s0);
s_s1 =
BinaryOperator::Create(Instruction::LShr, b_op1,
ConstantInt::get(b_op1->getType(), op_size - 1));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), s_s1);
t_s1 = new TruncInst(s_s1, Int1Ty);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), t_s1);
/* compare of the sign bits */
icmp_sign_bit =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, t_s0, t_s1);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()),
icmp_sign_bit);
/* create a new basic block which is executed if the signedness bits are
* equal */
BasicBlock *signequal_bb =
BasicBlock::Create(C, "signequal", end_bb->getParent(), end_bb);
BranchInst::Create(end_bb, signequal_bb);
/* create a new bb which is executed if exponents are satisfying the compare
*/
BasicBlock *middle_bb =
BasicBlock::Create(C, "injected", end_bb->getParent(), end_bb);
BranchInst::Create(end_bb, middle_bb);
auto term = bb->getTerminator();
/* if the signs are different goto end_bb else to signequal_bb */
BranchInst::Create(signequal_bb, end_bb, icmp_sign_bit, bb);
term->eraseFromParent();
/* insert code for equal signs */
/* isolate the exponents */
Instruction *s_e0, *m_e0, *t_e0, *s_e1, *m_e1, *t_e1;
s_e0 = BinaryOperator::Create(
Instruction::LShr, b_op0,
ConstantInt::get(b_op0->getType(), shiftR_exponent));
s_e1 = BinaryOperator::Create(
Instruction::LShr, b_op1,
ConstantInt::get(b_op1->getType(), shiftR_exponent));
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()), s_e0);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()), s_e1);
t_e0 = new TruncInst(s_e0, IntExponentTy);
t_e1 = new TruncInst(s_e1, IntExponentTy);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()), t_e0);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()), t_e1);
if (sizeInBits - precision < exTySizeBytes * 8) {
m_e0 = BinaryOperator::Create(
Instruction::And, t_e0,
ConstantInt::get(t_e0->getType(), mask_exponent));
m_e1 = BinaryOperator::Create(
Instruction::And, t_e1,
ConstantInt::get(t_e1->getType(), mask_exponent));
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()), m_e0);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()), m_e1);
} else {
m_e0 = t_e0;
m_e1 = t_e1;
}
/* compare the exponents of the operands */
Instruction *icmp_exponents_equal;
Instruction *icmp_exponent_result;
BasicBlock * signequal2_bb = signequal_bb;
switch (FcmpInst->getPredicate()) {
case CmpInst::FCMP_UEQ:
case CmpInst::FCMP_OEQ:
icmp_exponent_result =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, m_e0, m_e1);
break;
case CmpInst::FCMP_ONE:
case CmpInst::FCMP_UNE:
icmp_exponent_result =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_NE, m_e0, m_e1);
break;
/* compare the exponents of the operands (signs are equal)
* if exponents are equal -> proceed to mantissa comparison
* else get result depending on sign
*/
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT:
Instruction *icmp_exponent;
icmp_exponents_equal =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, m_e0, m_e1);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()),
icmp_exponents_equal);
// shortcut for unequal exponents
signequal2_bb = signequal_bb->splitBasicBlock(
BasicBlock::iterator(signequal_bb->getTerminator()));
/* if the exponents are equal goto middle_bb else to signequal2_bb */
term = signequal_bb->getTerminator();
BranchInst::Create(middle_bb, signequal2_bb, icmp_exponents_equal,
signequal_bb);
term->eraseFromParent();
icmp_exponent =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_UGT, m_e0, m_e1);
signequal2_bb->getInstList().insert(
BasicBlock::iterator(signequal2_bb->getTerminator()),
icmp_exponent);
icmp_exponent_result =
BinaryOperator::Create(Instruction::Xor, icmp_exponent, t_s0);
break;
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_ULT:
icmp_exponents_equal =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, m_e0, m_e1);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()),
icmp_exponents_equal);
// shortcut for unequal exponents
signequal2_bb = signequal_bb->splitBasicBlock(
BasicBlock::iterator(signequal_bb->getTerminator()));
/* if the exponents are equal goto middle_bb else to signequal2_bb */
term = signequal_bb->getTerminator();
BranchInst::Create(middle_bb, signequal2_bb, icmp_exponents_equal,
signequal_bb);
term->eraseFromParent();
icmp_exponent =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULT, m_e0, m_e1);
signequal2_bb->getInstList().insert(
BasicBlock::iterator(signequal2_bb->getTerminator()),
icmp_exponent);
icmp_exponent_result =
BinaryOperator::Create(Instruction::Xor, icmp_exponent, t_s0);
break;
default:
continue;
}
signequal2_bb->getInstList().insert(
BasicBlock::iterator(signequal2_bb->getTerminator()),
icmp_exponent_result);
{
term = signequal2_bb->getTerminator();
switch (FcmpInst->getPredicate()) {
case CmpInst::FCMP_UEQ:
case CmpInst::FCMP_OEQ:
/* if the exponents are satifying the compare do a fraction cmp in
* middle_bb */
BranchInst::Create(middle_bb, end_bb, icmp_exponent_result,
signequal2_bb);
break;
case CmpInst::FCMP_ONE:
case CmpInst::FCMP_UNE:
/* if the exponents are satifying the compare do a fraction cmp in
* middle_bb */
BranchInst::Create(end_bb, middle_bb, icmp_exponent_result,
signequal2_bb);
break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT:
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_ULT:
BranchInst::Create(end_bb, signequal2_bb);
break;
default:
continue;
}
term->eraseFromParent();
}
/* isolate the mantissa aka fraction */
Instruction *t_f0, *t_f1;
bool needTrunc = IntFractionTy->getPrimitiveSizeInBits() < op_size;
if (precision - 1 < frTySizeBytes * 8) {
Instruction *m_f0, *m_f1;
m_f0 = BinaryOperator::Create(
Instruction::And, b_op0,
ConstantInt::get(b_op0->getType(), mask_fraction));
m_f1 = BinaryOperator::Create(
Instruction::And, b_op1,
ConstantInt::get(b_op1->getType(), mask_fraction));
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), m_f0);
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), m_f1);
if (needTrunc) {
t_f0 = new TruncInst(m_f0, IntFractionTy);
t_f1 = new TruncInst(m_f1, IntFractionTy);
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), t_f0);
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), t_f1);
} else {
t_f0 = m_f0;
t_f1 = m_f1;
}
} else {
if (needTrunc) {
t_f0 = new TruncInst(b_op0, IntFractionTy);
t_f1 = new TruncInst(b_op1, IntFractionTy);
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), t_f0);
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), t_f1);
} else {
t_f0 = b_op0;
t_f1 = b_op1;
}
}
/* compare the fractions of the operands */
Instruction *icmp_fraction_result;
BasicBlock * middle2_bb = middle_bb;
PHINode * PN2 = nullptr;
switch (FcmpInst->getPredicate()) {
case CmpInst::FCMP_UEQ:
case CmpInst::FCMP_OEQ:
icmp_fraction_result =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, t_f0, t_f1);
middle2_bb->getInstList().insert(
BasicBlock::iterator(middle2_bb->getTerminator()),
icmp_fraction_result);
break;
case CmpInst::FCMP_UNE:
case CmpInst::FCMP_ONE:
icmp_fraction_result =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_NE, t_f0, t_f1);
middle2_bb->getInstList().insert(
BasicBlock::iterator(middle2_bb->getTerminator()),
icmp_fraction_result);
break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT:
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_ULT: {
Instruction *icmp_fraction_result2;
middle2_bb = middle_bb->splitBasicBlock(
BasicBlock::iterator(middle_bb->getTerminator()));
BasicBlock *negative_bb = BasicBlock::Create(
C, "negative_value", middle2_bb->getParent(), middle2_bb);
BasicBlock *positive_bb = BasicBlock::Create(
C, "positive_value", negative_bb->getParent(), negative_bb);
if (FcmpInst->getPredicate() == CmpInst::FCMP_OGT ||
FcmpInst->getPredicate() == CmpInst::FCMP_UGT) {
negative_bb->getInstList().push_back(
icmp_fraction_result = CmpInst::Create(
Instruction::ICmp, CmpInst::ICMP_ULT, t_f0, t_f1));
positive_bb->getInstList().push_back(
icmp_fraction_result2 = CmpInst::Create(
Instruction::ICmp, CmpInst::ICMP_UGT, t_f0, t_f1));
} else {
negative_bb->getInstList().push_back(
icmp_fraction_result = CmpInst::Create(
Instruction::ICmp, CmpInst::ICMP_UGT, t_f0, t_f1));
positive_bb->getInstList().push_back(
icmp_fraction_result2 = CmpInst::Create(
Instruction::ICmp, CmpInst::ICMP_ULT, t_f0, t_f1));
}
BranchInst::Create(middle2_bb, negative_bb);
BranchInst::Create(middle2_bb, positive_bb);
term = middle_bb->getTerminator();
BranchInst::Create(negative_bb, positive_bb, t_s0, middle_bb);
term->eraseFromParent();
PN2 = PHINode::Create(Int1Ty, 2, "");
PN2->addIncoming(icmp_fraction_result, negative_bb);
PN2->addIncoming(icmp_fraction_result2, positive_bb);
middle2_bb->getInstList().insert(
BasicBlock::iterator(middle2_bb->getTerminator()), PN2);
} break;
default:
continue;
}
PHINode *PN = PHINode::Create(Int1Ty, 3, "");
switch (FcmpInst->getPredicate()) {
case CmpInst::FCMP_UEQ:
case CmpInst::FCMP_OEQ:
/* unequal signs cannot be equal values */
/* goto false branch */
PN->addIncoming(ConstantInt::get(Int1Ty, 0), bb);
/* unequal exponents cannot be equal values, too */
PN->addIncoming(ConstantInt::get(Int1Ty, 0), signequal_bb);
/* fractions comparison */
PN->addIncoming(icmp_fraction_result, middle2_bb);
break;
case CmpInst::FCMP_ONE:
case CmpInst::FCMP_UNE:
/* unequal signs are unequal values */
/* goto true branch */
PN->addIncoming(ConstantInt::get(Int1Ty, 1), bb);
/* unequal exponents are unequal values, too */
PN->addIncoming(icmp_exponent_result, signequal_bb);
/* fractions comparison */
PN->addIncoming(icmp_fraction_result, middle2_bb);
break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT:
/* if op1 is negative goto true branch,
else go on comparing */
PN->addIncoming(t_s1, bb);
PN->addIncoming(icmp_exponent_result, signequal2_bb);
PN->addIncoming(PN2, middle2_bb);
break;
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_ULT:
/* if op0 is negative goto true branch,
else go on comparing */
PN->addIncoming(t_s0, bb);
PN->addIncoming(icmp_exponent_result, signequal2_bb);
PN->addIncoming(PN2, middle2_bb);
break;
default:
continue;
}
BasicBlock::iterator ii(FcmpInst);
ReplaceInstWithInst(FcmpInst->getParent()->getInstList(), ii, PN);
++count;
}
return count;
}
bool SplitComparesTransform::runOnModule(Module &M) {
char *bitw_env = getenv("AFL_LLVM_LAF_SPLIT_COMPARES_BITW");
if (!bitw_env) bitw_env = getenv("LAF_SPLIT_COMPARES_BITW");
if (bitw_env) { target_bitwidth = atoi(bitw_env); }
enableFPSplit = getenv("AFL_LLVM_LAF_SPLIT_FLOATS") != NULL;
if ((isatty(2) && getenv("AFL_QUIET") == NULL) ||
getenv("AFL_DEBUG") != NULL) {
errs() << "Split-compare-pass by laf.intel@gmail.com, extended by "
"heiko@hexco.de (splitting icmp to "
<< target_bitwidth << " bit)\n";
if (getenv("AFL_DEBUG") != NULL && !debug) { debug = 1; }
} else {
be_quiet = 1;
}
if (enableFPSplit) {
count = splitFPCompares(M);
/*
if (!be_quiet) {
errs() << "Split-floatingpoint-compare-pass: " << count
<< " FP comparisons split\n";
}
*/
simplifyFPCompares(M);
}
std::vector<CmpInst *> worklist;
/* iterate over all functions, bbs and instruction search for all integer
* compare instructions. Save them into the worklist for later. */
for (auto &F : M) {
if (!isInInstrumentList(&F)) continue;
for (auto &BB : F) {
for (auto &IN : BB) {
if (auto CI = dyn_cast<CmpInst>(&IN)) {
auto op0 = CI->getOperand(0);
auto op1 = CI->getOperand(1);
if (!op0 || !op1) { return false; }
auto iTy1 = dyn_cast<IntegerType>(op0->getType());
if (iTy1 && isa<IntegerType>(op1->getType())) {
unsigned bitw = iTy1->getBitWidth();
if (isSupportedBitWidth(bitw)) { worklist.push_back(CI); }
}
}
}
}
}
// now that we have a list of all integer comparisons we can start replacing
// them with the splitted alternatives.
for (auto CI : worklist) {
simplifyAndSplit(CI, M);
}
bool brokenDebug = false;
if (verifyModule(M, &errs()
#if LLVM_VERSION_MAJOR > 3 || \
(LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR >= 9)
,
&brokenDebug // 9th May 2016
#endif
)) {
reportError(
"Module Verifier failed! Consider reporting a bug with the AFL++ "
"project.",
nullptr, M);
}
if (brokenDebug) {
reportError("Module Verifier reported broken Debug Infos - Stripping!",
nullptr, M);
StripDebugInfo(M);
}
return true;
}
static void registerSplitComparesPass(const PassManagerBuilder &,
legacy::PassManagerBase &PM) {
PM.add(new SplitComparesTransform());
}
static RegisterStandardPasses RegisterSplitComparesPass(
PassManagerBuilder::EP_OptimizerLast, registerSplitComparesPass);
static RegisterStandardPasses RegisterSplitComparesTransPass0(
PassManagerBuilder::EP_EnabledOnOptLevel0, registerSplitComparesPass);
#if LLVM_VERSION_MAJOR >= 11
static RegisterStandardPasses RegisterSplitComparesTransPassLTO(
PassManagerBuilder::EP_FullLinkTimeOptimizationLast,
registerSplitComparesPass);
#endif
static RegisterPass<SplitComparesTransform> X("splitcompares",
"AFL++ split compares",
true /* Only looks at CFG */,
true /* Analysis Pass */);
