char TrueRandomClass::randomByte(void) {
char result;
uint8_t i;
result = 0;
for (i=8; i--;) result += result + randomBit();
return result;
}
long TrueRandomClass::random(long howBig) {
long randomValue;
long maxRandomValue;
long topBit;
long bitPosition;
if (!howBig) return 0;
randomValue = 0;
if (howBig & (howBig-1)) {
// Range is not a power of 2 - use slow method
topBit = howBig-1;
topBit |= topBit>>1;
topBit |= topBit>>2;
topBit |= topBit>>4;
topBit |= topBit>>8;
topBit |= topBit>>16;
topBit = (topBit+1) >> 1;
bitPosition = topBit;
do {
// Generate the next bit of the result
if (randomBit()) randomValue |= bitPosition;
// Check if bit
if (randomValue >= howBig) {
// Number is over the top limit - start again.
randomValue = 0;
bitPosition = topBit;
} else {
// Repeat for next bit
bitPosition >>= 1;
}
} while (bitPosition);
} else {
long TrueRandomClass::random() {
long result;
uint8_t i;
result = 0;
for (i=31; i--;) result += result + randomBit();
return result;
}
int TrueRandomClass::rand() {
int result;
uint8_t i;
result = 0;
for (i=15; i--;) result += result + randomBit();
return result;
}
static void randomize(const Instruction &Instr, const Variable &Var,
llvm::MCOperand &AssignedValue,
const llvm::BitVector &ForbiddenRegs) {
const Operand &Op = Instr.getPrimaryOperand(Var);
switch (Op.getExplicitOperandInfo().OperandType) {
case llvm::MCOI::OperandType::OPERAND_IMMEDIATE:
// FIXME: explore immediate values too.
AssignedValue = llvm::MCOperand::createImm(1);
break;
case llvm::MCOI::OperandType::OPERAND_REGISTER: {
assert(Op.isReg());
auto AllowedRegs = Op.getRegisterAliasing().sourceBits();
assert(AllowedRegs.size() == ForbiddenRegs.size());
for (auto I : ForbiddenRegs.set_bits())
AllowedRegs.reset(I);
AssignedValue = llvm::MCOperand::createReg(randomBit(AllowedRegs));
break;
}
default:
break;
}
}
llvm::Expected<std::vector<CodeTemplate>>
UopsSnippetGenerator::generateCodeTemplates(const Instruction &Instr) const {
CodeTemplate CT;
const llvm::BitVector *ScratchSpaceAliasedRegs = nullptr;
if (Instr.hasMemoryOperands()) {
const auto &ET = State.getExegesisTarget();
CT.ScratchSpacePointerInReg =
ET.getScratchMemoryRegister(State.getTargetMachine().getTargetTriple());
if (CT.ScratchSpacePointerInReg == 0)
return llvm::make_error<BenchmarkFailure>(
"Infeasible : target does not support memory instructions");
ScratchSpaceAliasedRegs =
&State.getRATC().getRegister(CT.ScratchSpacePointerInReg).aliasedBits();
// If the instruction implicitly writes to ScratchSpacePointerInReg , abort.
// FIXME: We could make a copy of the scratch register.
for (const auto &Op : Instr.Operands) {
if (Op.isDef() && Op.isImplicitReg() &&
ScratchSpaceAliasedRegs->test(Op.getImplicitReg()))
return llvm::make_error<BenchmarkFailure>(
"Infeasible : memory instruction uses scratch memory register");
}
}
const AliasingConfigurations SelfAliasing(Instr, Instr);
InstructionTemplate IT(Instr);
if (SelfAliasing.empty()) {
CT.Info = "instruction is parallel, repeating a random one.";
CT.Instructions.push_back(std::move(IT));
instantiateMemoryOperands(CT.ScratchSpacePointerInReg, CT.Instructions);
return getSingleton(std::move(CT));
}
if (SelfAliasing.hasImplicitAliasing()) {
CT.Info = "instruction is serial, repeating a random one.";
CT.Instructions.push_back(std::move(IT));
instantiateMemoryOperands(CT.ScratchSpacePointerInReg, CT.Instructions);
return getSingleton(std::move(CT));
}
const auto TiedVariables = getVariablesWithTiedOperands(Instr);
if (!TiedVariables.empty()) {
CT.Info = "instruction has tied variables, using static renaming.";
CT.Instructions = generateSnippetUsingStaticRenaming(
State, IT, TiedVariables, ScratchSpaceAliasedRegs);
instantiateMemoryOperands(CT.ScratchSpacePointerInReg, CT.Instructions);
return getSingleton(std::move(CT));
}
const auto &ReservedRegisters = State.getRATC().reservedRegisters();
// No tied variables, we pick random values for defs.
llvm::BitVector Defs(State.getRegInfo().getNumRegs());
for (const auto &Op : Instr.Operands) {
if (Op.isReg() && Op.isExplicit() && Op.isDef() && !Op.isMemory()) {
auto PossibleRegisters = Op.getRegisterAliasing().sourceBits();
remove(PossibleRegisters, ReservedRegisters);
// Do not use the scratch memory address register.
if (ScratchSpaceAliasedRegs)
remove(PossibleRegisters, *ScratchSpaceAliasedRegs);
assert(PossibleRegisters.any() && "No register left to choose from");
const auto RandomReg = randomBit(PossibleRegisters);
Defs.set(RandomReg);
IT.getValueFor(Op) = llvm::MCOperand::createReg(RandomReg);
}
}
// And pick random use values that are not reserved and don't alias with defs.
const auto DefAliases = getAliasedBits(State.getRegInfo(), Defs);
for (const auto &Op : Instr.Operands) {
if (Op.isReg() && Op.isExplicit() && Op.isUse() && !Op.isMemory()) {
auto PossibleRegisters = Op.getRegisterAliasing().sourceBits();
remove(PossibleRegisters, ReservedRegisters);
// Do not use the scratch memory address register.
if (ScratchSpaceAliasedRegs)
remove(PossibleRegisters, *ScratchSpaceAliasedRegs);
remove(PossibleRegisters, DefAliases);
assert(PossibleRegisters.any() && "No register left to choose from");
const auto RandomReg = randomBit(PossibleRegisters);
IT.getValueFor(Op) = llvm::MCOperand::createReg(RandomReg);
}
}
CT.Info =
"instruction has no tied variables picking Uses different from defs";
CT.Instructions.push_back(std::move(IT));
instantiateMemoryOperands(CT.ScratchSpacePointerInReg, CT.Instructions);
return getSingleton(std::move(CT));
}