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Optimize JUMPDEST analysis #306

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Apr 22, 2021
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Optimize JUMPDEST analysis #306

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17 changes: 11 additions & 6 deletions lib/evmone/baseline.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12,16 +12,21 @@ namespace evmone
{
JumpdestMap build_jumpdest_map(const uint8_t* code, size_t code_size)
{
JumpdestMap m(code_size);
// Bitmask for PUSH opcode identification.
// It clears the lower 5 bits of a byte.
// The opcode is PUSH iff remaining byte value is 0x60 (OP_PUSH1).
constexpr auto push_op_mask = 0xE0;

JumpdestMap map(code_size); // Allocate and init bitmap with zeros.
for (size_t i = 0; i < code_size; ++i)
{
const auto op = code[i];
if (op == OP_JUMPDEST)
m[i] = true;
else if (op >= OP_PUSH1 && op <= OP_PUSH32)
i += op - size_t{OP_PUSH1 - 1};
if ((op & push_op_mask) == OP_PUSH1) // If any PUSH opcode.
i += op - size_t{OP_PUSH1 - 1}; // Skip PUSH data.
else if (INTX_UNLIKELY(op == OP_JUMPDEST))
map[i] = true;
}
return m;
return map;
}

namespace
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