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split-compares-pass.so.cc
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/*
* 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
*
* http://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"
namespace {
class SplitComparesTransform : public ModulePass {
public:
static char ID;
SplitComparesTransform() : ModulePass(ID) {
initInstrumentList();
}
bool runOnModule(Module &M) override;
#if LLVM_VERSION_MAJOR >= 4
StringRef getPassName() const override {
#else
const char *getPassName() const override {
#endif
return "simplifies and splits ICMP instructions";
}
protected:
int be_quiet = 0;
private:
int enableFPSplit;
size_t splitIntCompares(Module &M, unsigned bitw);
size_t splitFPCompares(Module &M);
bool simplifyCompares(Module &M);
bool simplifyIntSignedness(Module &M);
size_t nextPowerOfTwo(size_t in);
};
} // namespace
char SplitComparesTransform::ID = 0;
/* This function splits ICMP instructions with xGE or xLE predicates into two
* ICMP instructions with predicate xGT or xLT and EQ */
bool SplitComparesTransform::simplifyCompares(Module &M) {
LLVMContext & C = M.getContext();
std::vector<Instruction *> icomps;
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 (selectcmpInst->getPredicate() == CmpInst::ICMP_UGE ||
selectcmpInst->getPredicate() == CmpInst::ICMP_SGE ||
selectcmpInst->getPredicate() == CmpInst::ICMP_ULE ||
selectcmpInst->getPredicate() == CmpInst::ICMP_SLE) {
auto op0 = selectcmpInst->getOperand(0);
auto op1 = selectcmpInst->getOperand(1);
IntegerType *intTyOp0 = dyn_cast<IntegerType>(op0->getType());
IntegerType *intTyOp1 = dyn_cast<IntegerType>(op1->getType());
/* this is probably not needed but we do it anyway */
if (!intTyOp0 || !intTyOp1) { continue; }
icomps.push_back(selectcmpInst);
}
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 (!icomps.size() && !fcomps.size()) { return false; }
for (auto &IcmpInst : icomps) {
BasicBlock *bb = IcmpInst->getParent();
auto op0 = IcmpInst->getOperand(0);
auto op1 = IcmpInst->getOperand(1);
/* find out what the new predicate is going to be */
auto pred = dyn_cast<CmpInst>(IcmpInst)->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
continue;
}
/* 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 */
Instruction *icmp_np;
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 */
Instruction *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);
}
/* now 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 pred = dyn_cast<CmpInst>(FcmpInst)->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 icmp 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 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 */
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 icmp. 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 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(fcmp_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(FcmpInst);
ReplaceInstWithInst(FcmpInst->getParent()->getInstList(), ii, PN);
}
return true;
}
/* this function transforms signed compares to equivalent unsigned compares */
bool SplitComparesTransform::simplifyIntSignedness(Module &M) {
LLVMContext & C = M.getContext();
std::vector<Instruction *> icomps;
IntegerType * Int1Ty = IntegerType::getInt1Ty(C);
/* iterate over all functions, bbs and instructions and add
* all signed compares to icomps vector */
for (auto &F : M) {
for (auto &BB : F) {
for (auto &IN : BB) {
CmpInst *selectcmpInst = nullptr;
if ((selectcmpInst = dyn_cast<CmpInst>(&IN))) {
if (selectcmpInst->getPredicate() == CmpInst::ICMP_SGT ||
selectcmpInst->getPredicate() == CmpInst::ICMP_SLT) {
auto op0 = selectcmpInst->getOperand(0);
auto op1 = selectcmpInst->getOperand(1);
IntegerType *intTyOp0 = dyn_cast<IntegerType>(op0->getType());
IntegerType *intTyOp1 = dyn_cast<IntegerType>(op1->getType());
/* see above */
if (!intTyOp0 || !intTyOp1) { continue; }
/* i think this is not possible but to lazy to look it up */
if (intTyOp0->getBitWidth() != intTyOp1->getBitWidth()) {
continue;
}
icomps.push_back(selectcmpInst);
}
}
}
}
}
if (!icomps.size()) { return false; }
for (auto &IcmpInst : icomps) {
BasicBlock *bb = IcmpInst->getParent();
auto op0 = IcmpInst->getOperand(0);
auto op1 = IcmpInst->getOperand(1);
IntegerType *intTyOp0 = dyn_cast<IntegerType>(op0->getType());
unsigned bitw = intTyOp0->getBitWidth();
IntegerType *IntType = IntegerType::get(C, bitw);
/* get the new predicate */
auto pred = dyn_cast<CmpInst>(IcmpInst)->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.*/
Instruction *s_op0, *t_op0, *s_op1, *t_op1, *icmp_sign_bit;
s_op0 = BinaryOperator::Create(Instruction::LShr, op0,
ConstantInt::get(IntType, bitw - 1));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), s_op0);
t_op0 = new TruncInst(s_op0, Int1Ty);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), t_op0);
s_op1 = BinaryOperator::Create(Instruction::LShr, op1,
ConstantInt::get(IntType, bitw - 1));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), s_op1);
t_op1 = new TruncInst(s_op1, Int1Ty);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), t_op1);
/* compare of the sign bits */
icmp_sign_bit =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, t_op0, t_op1);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()),
icmp_sign_bit);
/* create a new basic block which is executed if the signedness bit is
* different */
Instruction *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 */
Instruction *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);
}
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) {
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_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();
const unsigned int precision =
sizeInBits == 32
? 24
: sizeInBits == 64
? 53
: sizeInBits == 128 ? 113
: sizeInBits == 16 ? 11
/* sizeInBits == 80 */
: 65;
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 equal */
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_exponent_result;
switch (FcmpInst->getPredicate()) {
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;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT:
Instruction *icmp_exponent;
icmp_exponent =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_UGT, m_e0, m_e1);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_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_exponent =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULT, m_e0, m_e1);
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()), icmp_exponent);
icmp_exponent_result =
BinaryOperator::Create(Instruction::Xor, icmp_exponent, t_s0);
break;
default:
continue;
}
signequal_bb->getInstList().insert(
BasicBlock::iterator(signequal_bb->getTerminator()),
icmp_exponent_result);
{
auto term = signequal_bb->getTerminator();
/* if the exponents are different do a fraction cmp */
BranchInst::Create(middle_bb, end_bb, icmp_exponent_result, signequal_bb);
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;
switch (FcmpInst->getPredicate()) {
case CmpInst::FCMP_OEQ:
icmp_fraction_result =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, t_f0, t_f1);
break;
case CmpInst::FCMP_UNE:
case CmpInst::FCMP_ONE:
icmp_fraction_result =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_NE, t_f0, t_f1);
break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT:
Instruction *icmp_fraction;
icmp_fraction =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_UGT, t_f0, t_f1);
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), icmp_fraction);
icmp_fraction_result =
BinaryOperator::Create(Instruction::Xor, icmp_fraction, t_s0);
break;
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_ULT:
icmp_fraction =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULT, t_f0, t_f1);
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), icmp_fraction);
icmp_fraction_result =
BinaryOperator::Create(Instruction::Xor, icmp_fraction, t_s0);
break;
default:
continue;
}
middle_bb->getInstList().insert(
BasicBlock::iterator(middle_bb->getTerminator()), icmp_fraction_result);
PHINode *PN = PHINode::Create(Int1Ty, 3, "");
switch (FcmpInst->getPredicate()) {
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, middle_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(ConstantInt::get(Int1Ty, 1), signequal_bb);
/* fractions comparison */
PN->addIncoming(icmp_fraction_result, middle_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, signequal_bb);
PN->addIncoming(icmp_fraction_result, middle_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, signequal_bb);
PN->addIncoming(icmp_fraction_result, middle_bb);
break;
default:
continue;
}
BasicBlock::iterator ii(FcmpInst);
ReplaceInstWithInst(FcmpInst->getParent()->getInstList(), ii, PN);
++count;
}
return count;
}
/* splits icmps of size bitw into two nested icmps with bitw/2 size each */
size_t SplitComparesTransform::splitIntCompares(Module &M, unsigned bitw) {
size_t count = 0;
LLVMContext &C = M.getContext();
IntegerType *Int1Ty = IntegerType::getInt1Ty(C);
IntegerType *OldIntType = IntegerType::get(C, bitw);
IntegerType *NewIntType = IntegerType::get(C, bitw / 2);
std::vector<Instruction *> icomps;
if (bitw % 2) { return 0; }
/* not supported yet */
if (bitw > 64) { return 0; }
/* get all EQ, NE, UGT, and ULT icmps of width bitw. if the
* functions simplifyCompares() and simplifyIntSignedness()
* were executed only these four predicates should exist */
for (auto &F : M) {
for (auto &BB : F) {
for (auto &IN : BB) {
CmpInst *selectcmpInst = nullptr;
if ((selectcmpInst = dyn_cast<CmpInst>(&IN))) {
if (selectcmpInst->getPredicate() == CmpInst::ICMP_EQ ||
selectcmpInst->getPredicate() == CmpInst::ICMP_NE ||
selectcmpInst->getPredicate() == CmpInst::ICMP_UGT ||
selectcmpInst->getPredicate() == CmpInst::ICMP_ULT) {
auto op0 = selectcmpInst->getOperand(0);
auto op1 = selectcmpInst->getOperand(1);
IntegerType *intTyOp0 = dyn_cast<IntegerType>(op0->getType());
IntegerType *intTyOp1 = dyn_cast<IntegerType>(op1->getType());
if (!intTyOp0 || !intTyOp1) { continue; }
/* check if the bitwidths are the one we are looking for */
if (intTyOp0->getBitWidth() != bitw ||
intTyOp1->getBitWidth() != bitw) {
continue;
}
icomps.push_back(selectcmpInst);
}
}
}
}
}
if (!icomps.size()) { return 0; }
for (auto &IcmpInst : icomps) {
BasicBlock *bb = IcmpInst->getParent();
auto op0 = IcmpInst->getOperand(0);
auto op1 = IcmpInst->getOperand(1);
auto pred = dyn_cast<CmpInst>(IcmpInst)->getPredicate();
BasicBlock *end_bb = bb->splitBasicBlock(BasicBlock::iterator(IcmpInst));
/* create the comparison of the top halves of the original operands */
Instruction *s_op0, *op0_high, *s_op1, *op1_high, *icmp_high;
s_op0 = BinaryOperator::Create(Instruction::LShr, op0,
ConstantInt::get(OldIntType, bitw / 2));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), s_op0);
op0_high = new TruncInst(s_op0, NewIntType);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()),
op0_high);
s_op1 = BinaryOperator::Create(Instruction::LShr, op1,
ConstantInt::get(OldIntType, bitw / 2));
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), s_op1);
op1_high = new TruncInst(s_op1, NewIntType);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()),
op1_high);
icmp_high = CmpInst::Create(Instruction::ICmp, pred, op0_high, op1_high);
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()),
icmp_high);
/* now we have to destinguish between == != and > < */
if (pred == CmpInst::ICMP_EQ || pred == CmpInst::ICMP_NE) {
/* transformation for == and != icmps */
/* create a compare for the lower half of the original operands */
Instruction *op0_low, *op1_low, *icmp_low;
BasicBlock * cmp_low_bb =