Review comments.

This commit is contained in:
chriseth 2019-02-18 15:16:14 +01:00
parent 5eb155b894
commit 0e471ab811
3 changed files with 19 additions and 12 deletions

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@ -3,7 +3,6 @@ set(sources
EVMInstructionInterpreter.cpp
Interpreter.h
Interpreter.cpp
)
add_library(yulInterpreter ${sources})

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@ -50,6 +50,9 @@ u256 exp256(u256 _base, u256 _exponent)
return result;
}
/// Reads 32 bytes from @a _data at position @a _offset bytes while
/// interpreting @a _data to be padded with an infinite number of zero
/// bytes beyond its end.
u256 readZeroExtended(bytes const& _data, u256 const& _offset)
{
if (_offset >= _data.size())
@ -70,6 +73,10 @@ u256 readZeroExtended(bytes const& _data, u256 const& _offset)
}
}
/// Copy @a _size bytes of @a _source at offset @a _sourceOffset to
/// @a _target at offset @a _targetOffset. Behaves as if @a _source would
/// continue with an infinite sequence of zero bytes beyond its end.
/// Asserts the target is large enough to hold the copied segment.
void copyZeroExtended(
bytes& _target, bytes const& _source,
size_t _targetOffset, size_t _sourceOffset, size_t _size
@ -137,11 +144,11 @@ u256 EVMInstructionInterpreter::eval(
case Instruction::XOR:
return arg[0] ^ arg[1];
case Instruction::BYTE:
return arg[0] >= 32 ? 0 : (arg[1] >> unsigned(8 * (31 - (arg[0] & 0xff)))) & 0xff;
return arg[0] >= 32 ? 0 : (arg[1] >> unsigned(8 * (31 - arg[0]))) & 0xff;
case Instruction::SHL:
return arg[0] > 255 ? 0 : (arg[1] << unsigned(arg[0] & 0xff));
return arg[0] > 255 ? 0 : (arg[1] << unsigned(arg[0]));
case Instruction::SHR:
return arg[0] > 255 ? 0 : (arg[1] >> unsigned(arg[0] & 0xff));
return arg[0] > 255 ? 0 : (arg[1] >> unsigned(arg[0]));
case Instruction::SAR:
{
static u256 const hibit = u256(1) << 255;
@ -149,7 +156,7 @@ u256 EVMInstructionInterpreter::eval(
return arg[1] & hibit ? u256(-1) : 0;
else
{
unsigned amount = unsigned(arg[0] & 0xff);
unsigned amount = unsigned(arg[0]);
u256 v = arg[1] >> amount;
if (arg[1] & hibit)
v |= u256(-1) << (256 - amount);
@ -165,7 +172,7 @@ u256 EVMInstructionInterpreter::eval(
return arg[0];
else
{
unsigned testBit = unsigned(arg[0] & 0xff) * 8 + 7;
unsigned testBit = unsigned(arg[0]) * 8 + 7;
u256 ret = arg[1];
u256 mask = ((u256(1) << testBit) - 1);
if (boost::multiprecision::bit_test(ret, testBit))

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@ -45,19 +45,20 @@ struct InterpreterState;
* Interprets EVM instructions based on the current state and logs instructions with
* side-effects.
*
* Since this is mainly meant to be used for testing, it is focused on a single
* contract only, does not do any gas counting and differs from the correct
* implementation in the following ways:
* Since this is mainly meant to be used for differential fuzz testing, it is focused
* on a single contract only, does not do any gas counting and differs from the correct
* implementation in many ways:
*
* - If memory access to a "large" memory position is performed, a deterministic
* value is returned. Data that is stored in a "large" memory position is not
* retained.
* value is returned. Data that is stored in a "large" memory position is not
* retained.
* - The blockhash instruction returns a fixed value if the argument is in range.
* - Extcodesize returns a deterministic value depending on the address.
* - Extcodecopy copies a deterministic value depending on the address.
* - And many other things
* - TODO
*
* The main focus is that the generated execution trace is the same for equivalent executions
* and likely to be different for non-eqivalent executions.
*/
class EVMInstructionInterpreter
{