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split-compares-pass.so.cc
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/*
* Copyright 2016 laf-intel
* extended for floating point by Heiko Eißfeldt
* adapted to new pass manager 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"
#if LLVM_MAJOR >= 11
#include "llvm/Passes/PassPlugin.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/IR/PassManager.h"
#else
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#endif
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/IR/Module.h"
#if LLVM_VERSION_MAJOR >= 14 /* how about stable interfaces? */
#include "llvm/Passes/OptimizationLevel.h"
#endif
#include "llvm/IR/IRBuilder.h"
#if LLVM_VERSION_MAJOR >= 4 || \
(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 {
#if LLVM_MAJOR >= 11
class SplitComparesTransform : public PassInfoMixin<SplitComparesTransform> {
public:
// static char ID;
SplitComparesTransform() : enableFPSplit(0) {
#else
class SplitComparesTransform : public ModulePass {
public:
static char ID;
SplitComparesTransform() : ModulePass(ID), enableFPSplit(0) {
#endif
initInstrumentList();
}
#if LLVM_MAJOR >= 11
PreservedAnalyses run(Module &M, ModuleAnalysisManager &MAM);
#else
bool runOnModule(Module &M) override;
#endif
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
#if LLVM_MAJOR >= 11
extern "C" ::llvm::PassPluginLibraryInfo LLVM_ATTRIBUTE_WEAK
llvmGetPassPluginInfo() {
return {LLVM_PLUGIN_API_VERSION, "splitcompares", "v0.1",
/* lambda to insert our pass into the pass pipeline. */
[](PassBuilder &PB) {
#if 1
#if LLVM_VERSION_MAJOR <= 13
using OptimizationLevel = typename PassBuilder::OptimizationLevel;
#endif
PB.registerOptimizerLastEPCallback(
[](ModulePassManager &MPM, OptimizationLevel OL) {
MPM.addPass(SplitComparesTransform());
});
/* TODO LTO registration */
#else
using PipelineElement = typename PassBuilder::PipelineElement;
PB.registerPipelineParsingCallback([](StringRef Name,
ModulePassManager &MPM,
ArrayRef<PipelineElement>) {
if (Name == "splitcompares") {
MPM.addPass(SplitComparesTransform());
return true;
} else {
return false;
}
});
#endif
}};
}
#else
char SplitComparesTransform::ID = 0;
#endif
/// 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, MNAME)) 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);
#if LLVM_MAJOR >= 16
fcmp_np->insertInto(bb, BasicBlock::iterator(bb->getTerminator()));
#else
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()),
fcmp_np);
#endif
/* 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);
#if LLVM_MAJOR >= 16
fcmp_eq->insertInto(middle_bb, middle_bb->end());
#else
middle_bb->getInstList().push_back(fcmp_eq);
#endif
/* 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);
#if LLVM_MAJOR >= 16
ReplaceInstWithInst(FcmpInst->getParent(), ii, PN);
#else
ReplaceInstWithInst(FcmpInst->getParent()->getInstList(), ii, PN);
#endif
}
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);
#if LLVM_MAJOR >= 16
icmp_np->insertInto(bb, BasicBlock::iterator(bb->getTerminator()));
#else
bb->getInstList().insert(BasicBlock::iterator(bb->getTerminator()), icmp_np);
#endif
/* 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);
#if LLVM_MAJOR >= 16
icmp_eq->insertInto(middle_bb, middle_bb->end());
#else
middle_bb->getInstList().push_back(icmp_eq);
#endif
/* 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);
#if LLVM_MAJOR >= 16
ReplaceInstWithInst(IcmpInst->getParent(), ii, PN);
#else
ReplaceInstWithInst(IcmpInst->getParent()->getInstList(), ii, PN);
#endif
if (new_pred == CmpInst::ICMP_SGT || new_pred == CmpInst::ICMP_SLT) {
simplifySignedCompare(icmp_np, M, worklist);
}
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);
}
#if LLVM_MAJOR >= 16
icmp_inv_sig_cmp->insertInto(sign_bb, sign_bb->end());
#else
sign_bb->getInstList().push_back(icmp_inv_sig_cmp);
#endif
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);
#if LLVM_MAJOR >= 16
icmp_usign_cmp->insertInto(middle_bb, middle_bb->end());
#else
middle_bb->getInstList().push_back(icmp_usign_cmp);
#endif
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);
#if LLVM_MAJOR >= 16
ReplaceInstWithInst(IcmpInst->getParent(), ii, PN);
#else
ReplaceInstWithInst(IcmpInst->getParent()->getInstList(), ii, PN);
#endif
// 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:
case CmpInst::ICMP_UGE:
case CmpInst::ICMP_ULE:
case CmpInst::ICMP_SGT:
case CmpInst::ICMP_SLT:
case CmpInst::ICMP_SGE:
case CmpInst::ICMP_SLE:
break;
default:
if (!be_quiet)
fprintf(stderr, "Error: split-compare: Unsupported predicate (%u)\n",
pred);
// 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
if (!be_quiet)
fprintf(stderr, "Error: split-compare: not an integer type\n");
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_SGE:
case CmpInst::ICMP_SLE:
case CmpInst::ICMP_SGT:
case CmpInst::ICMP_SLT:
case CmpInst::ICMP_UGE:
case CmpInst::ICMP_ULE:
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 if (pred == CmpInst::ICMP_ULT) {
icmp_inv_cmp = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_UGT,
op0_high, op1_high);
} else {
// Never gonna appen
if (!be_quiet)
fprintf(stderr,
"Error: split-compare: Equals or signed not removed: %d\n",
pred);
}
#if LLVM_MAJOR >= 16
icmp_inv_cmp->insertInto(inv_cmp_bb, inv_cmp_bb->end());
#else
inv_cmp_bb->getInstList().push_back(icmp_inv_cmp);
#endif
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);
op1_low = new TruncInst(op1, NewIntType);
icmp_low = CmpInst::Create(Instruction::ICmp, pred, op0_low, op1_low);
#if LLVM_MAJOR >= 16
op0_low->insertInto(cmp_low_bb, cmp_low_bb->end());
op1_low->insertInto(cmp_low_bb, cmp_low_bb->end());
icmp_low->insertInto(cmp_low_bb, cmp_low_bb->end());
#else
cmp_low_bb->getInstList().push_back(op0_low);
cmp_low_bb->getInstList().push_back(op1_low);
cmp_low_bb->getInstList().push_back(icmp_low);
#endif
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:
if (!be_quiet)
fprintf(stderr, "Error: split-compare: should not happen\n");
return false;
}
BasicBlock::iterator ii(cmp_inst);
#if LLVM_MAJOR >= 16
ReplaceInstWithInst(cmp_inst->getParent(), ii, PN);
#else
ReplaceInstWithInst(cmp_inst->getParent()->getInstList(), ii, PN);
#endif
// We split the comparison into low and high. If this isn't our target
// bitwidth we recursively 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 >= 4 || \
(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, MNAME)) 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);
}
}