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Make small push value parsing endianness independent #178

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merged 3 commits into from
Sep 17, 2019
Merged

Make small push value parsing endianness independent #178

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2142392
Fix cast to broad in scope
chfast Sep 16, 2019
408ad24
Make small push value parsing endianness independent
chfast Sep 16, 2019
95b9b04
Find single push_end value
chfast Sep 17, 2019
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30 changes: 12 additions & 18 deletions lib/evmone/analysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -23,13 +23,6 @@ struct block_analysis
explicit block_analysis(size_t index) noexcept : begin_block_index{index} {}
};

inline constexpr uint64_t load64be(const unsigned char* data) noexcept
{
return uint64_t{data[7]} | (uint64_t{data[6]} << 8) | (uint64_t{data[5]} << 16) |
(uint64_t{data[4]} << 24) | (uint64_t{data[3]} << 32) | (uint64_t{data[2]} << 40) |
(uint64_t{data[1]} << 48) | (uint64_t{data[0]} << 56);
}

code_analysis analyze(evmc_revision rev, const uint8_t* code, size_t code_size) noexcept
{
static constexpr auto stack_req_max = std::numeric_limits<int16_t>::max();
Expand Down Expand Up @@ -91,22 +84,23 @@ code_analysis analyze(evmc_revision rev, const uint8_t* code, size_t code_size)

case ANY_SMALL_PUSH:
{
const auto push_size = size_t(opcode - OP_PUSH1 + 1);
const auto push_end = code_pos + push_size;

uint8_t value_bytes[8]{};
auto insert_pos = &value_bytes[sizeof(value_bytes) - push_size];

// TODO: Consier the same endianness-specific loop as in ANY_LARGE_PUSH case.
while (code_pos < push_end && code_pos < code_end)
*insert_pos++ = *code_pos++;
instr.arg.small_push_value = load64be(value_bytes);
const auto push_size = static_cast<size_t>(opcode - OP_PUSH1) + 1;
const auto push_end = std::min(code_pos + push_size, code_end);

uint64_t value = 0;
auto insert_bit_pos = (push_size - 1) * 8;
while (code_pos < push_end)
{
value |= uint64_t{*code_pos++} << insert_bit_pos;
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Could it still be in a separate helper function maybe?

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The load64be was only doing bswap. I would need to extract whole case:.

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I pushed an example how it could look like, but it is up to 30% slower.

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Wow then let's leave it, if it's so much slower (why, can't be inlined sometimes?)

push_end change looks fine, though

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I think returning multiple values and using tuple and std::tie messes it up. But I'm only guessing. I'd need much more time to investigate.

insert_bit_pos -= 8;
}
instr.arg.small_push_value = value;
break;
}

case ANY_LARGE_PUSH:
{
const auto push_size = size_t(opcode - OP_PUSH1 + 1);
const auto push_size = static_cast<size_t>(opcode - OP_PUSH1) + 1;
const auto push_end = code_pos + push_size;

auto& push_value = analysis.push_values.emplace_back();
Expand Down