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Merge pull request #2261 from ethereum/asm-optimizer-rules

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Add more assembly optimizer rules
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Yoichi Hirai 2017-05-19 21:29:28 +02:00 committed by GitHub
commit 7e7c00f761
1 changed files with 19 additions and 10 deletions
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29
libevmasm/SimplificationRules.cpp
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@ -103,7 +103,7 @@ Rules::Rules()
{{Instruction::SMOD, {A, B}}, [=]{ return B.d() == 0 ? 0 : s2u(modWorkaround(u2s(A.d()), u2s(B.d()))); }},
{{Instruction::EXP, {A, B}}, [=]{ return u256(boost::multiprecision::powm(bigint(A.d()), bigint(B.d()), bigint(1) << 256)); }},
{{Instruction::NOT, {A}}, [=]{ return ~A.d(); }},
{{Instruction::LT, {A, B}}, [=]() { return A.d() < B.d() ? u256(1) : 0; }},
{{Instruction::LT, {A, B}}, [=]() -> u256 { return A.d() < B.d() ? 1 : 0; }},
{{Instruction::GT, {A, B}}, [=]() -> u256 { return A.d() > B.d() ? 1 : 0; }},
{{Instruction::SLT, {A, B}}, [=]() -> u256 { return u2s(A.d()) < u2s(B.d()) ? 1 : 0; }},
{{Instruction::SGT, {A, B}}, [=]() -> u256 { return u2s(A.d()) > u2s(B.d()) ? 1 : 0; }},
@ -124,23 +124,26 @@ Rules::Rules()
return u256(boost::multiprecision::bit_test(B.d(), testBit) ? B.d() | ~mask : B.d() & mask);
}},
// invariants involving known constants
// invariants involving known constants (commutative instructions will be checked with swapped operants too)
{{Instruction::ADD, {X, 0}}, [=]{ return X; }},
{{Instruction::SUB, {X, 0}}, [=]{ return X; }},
{{Instruction::MUL, {X, 1}}, [=]{ return X; }},
{{Instruction::DIV, {X, 1}}, [=]{ return X; }},
{{Instruction::SDIV, {X, 1}}, [=]{ return X; }},
{{Instruction::OR, {X, 0}}, [=]{ return X; }},
{{Instruction::XOR, {X, 0}}, [=]{ return X; }},
{{Instruction::AND, {X, ~u256(0)}}, [=]{ return X; }},
{{Instruction::AND, {X, 0}}, [=]{ return u256(0); }},
{{Instruction::MUL, {X, 0}}, [=]{ return u256(0); }},
{{Instruction::MUL, {X, 1}}, [=]{ return X; }},
{{Instruction::DIV, {X, 0}}, [=]{ return u256(0); }},
{{Instruction::DIV, {0, X}}, [=]{ return u256(0); }},
{{Instruction::DIV, {X, 1}}, [=]{ return X; }},
{{Instruction::SDIV, {X, 0}}, [=]{ return u256(0); }},
{{Instruction::SDIV, {0, X}}, [=]{ return u256(0); }},
{{Instruction::SDIV, {X, 1}}, [=]{ return X; }},
{{Instruction::AND, {X, ~u256(0)}}, [=]{ return X; }},
{{Instruction::AND, {X, 0}}, [=]{ return u256(0); }},
{{Instruction::OR, {X, 0}}, [=]{ return X; }},
{{Instruction::OR, {X, ~u256(0)}}, [=]{ return ~u256(0); }},
{{Instruction::XOR, {X, 0}}, [=]{ return X; }},
{{Instruction::MOD, {X, 0}}, [=]{ return u256(0); }},
{{Instruction::MOD, {0, X}}, [=]{ return u256(0); }},
{{Instruction::OR, {X, ~u256(0)}}, [=]{ return ~u256(0); }},
{{Instruction::EQ, {X, 0}}, [=]() -> Pattern { return {Instruction::ISZERO, {X}}; } },
// operations involving an expression and itself
{{Instruction::AND, {X, X}}, [=]{ return X; }},
{{Instruction::OR, {X, X}}, [=]{ return X; }},
@ -153,6 +156,7 @@ Rules::Rules()
{{Instruction::SGT, {X, X}}, [=]{ return u256(0); }},
{{Instruction::MOD, {X, X}}, [=]{ return u256(0); }},
// logical instruction combinations
{{Instruction::NOT, {{Instruction::NOT, {X}}}}, [=]{ return X; }},
{{Instruction::XOR, {{{X}, {Instruction::XOR, {X, Y}}}}}, [=]{ return Y; }},
{{Instruction::OR, {{{X}, {Instruction::AND, {X, Y}}}}}, [=]{ return X; }},
@ -160,6 +164,7 @@ Rules::Rules()
{{Instruction::AND, {{{X}, {Instruction::NOT, {X}}}}}, [=]{ return u256(0); }},
{{Instruction::OR, {{{X}, {Instruction::NOT, {X}}}}}, [=]{ return ~u256(0); }},
});
// Double negation of opcodes with binary result
for (auto const& op: vector<Instruction>{
Instruction::EQ,
@ -172,14 +177,17 @@ Rules::Rules()
{Instruction::ISZERO, {{Instruction::ISZERO, {{op, {X, Y}}}}}},
[=]() -> Pattern { return {op, {X, Y}}; }
});
addRule({
{Instruction::ISZERO, {{Instruction::ISZERO, {{Instruction::ISZERO, {X}}}}}},
[=]() -> Pattern { return {Instruction::ISZERO, {X}}; }
});
addRule({
{Instruction::ISZERO, {{Instruction::XOR, {X, Y}}}},
[=]() -> Pattern { return { Instruction::EQ, {X, Y} }; }
});
// Associative operations
for (auto const& opFun: vector<pair<Instruction,function<u256(u256 const&,u256 const&)>>>{
{Instruction::ADD, plus<u256>()},
@ -210,6 +218,7 @@ Rules::Rules()
[=]() -> Pattern { return {op, {{op, {X, Y}}, A}}; }
}});
}
// move constants across subtractions
addRules(vector<pair<Pattern, function<Pattern()>>>{
{