Merge pull request #7122 from sifmelcara/expression-inliner-avoid-dup-expr

[Yul] ExpressionInliner: avoid duplicating expressions
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Leonardo 2019-08-06 11:08:38 +02:00 committed by GitHub
commit cd563e526a
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4 changed files with 68 additions and 17 deletions

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@ -14,6 +14,7 @@ Compiler Features:
* Standard JSON Interface: Compile only selected sources and contracts.
* Standard JSON Interface: Provide secondary error locations (e.g. the source position of other conflicting declarations).
* SMTChecker: Do not erase knowledge about storage pointers if another storage pointer is assigned.
* Yul Optimizer: Do not inline function if it would result in expressions being duplicated that are not cheap.

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@ -21,11 +21,12 @@
#include <libyul/optimiser/ExpressionInliner.h>
#include <libyul/optimiser/InlinableExpressionFunctionFinder.h>
#include <libyul/optimiser/Metrics.h>
#include <libyul/optimiser/NameCollector.h>
#include <libyul/optimiser/Substitution.h>
#include <libyul/optimiser/Semantics.h>
#include <libyul/AsmData.h>
#include <boost/algorithm/cxx11/all_of.hpp>
#include <libyul/AsmData.h>
using namespace std;
using namespace dev;
@ -40,7 +41,6 @@ void ExpressionInliner::run()
(*this)(m_block);
}
void ExpressionInliner::operator()(FunctionDefinition& _fun)
{
ASTModifier::operator()(_fun);
@ -52,21 +52,28 @@ void ExpressionInliner::visit(Expression& _expression)
if (_expression.type() == typeid(FunctionCall))
{
FunctionCall& funCall = boost::get<FunctionCall>(_expression);
if (!m_inlinableFunctions.count(funCall.functionName.name))
return;
FunctionDefinition const& fun = *m_inlinableFunctions.at(funCall.functionName.name);
bool movable = boost::algorithm::all_of(
funCall.arguments,
[=](Expression const& _arg) { return SideEffectsCollector(m_dialect, _arg).movable(); }
);
if (m_inlinableFunctions.count(funCall.functionName.name) && movable)
map<YulString, Expression const*> substitutions;
for (size_t i = 0; i < funCall.arguments.size(); i++)
{
FunctionDefinition const& fun = *m_inlinableFunctions.at(funCall.functionName.name);
map<YulString, Expression const*> substitutions;
for (size_t i = 0; i < fun.parameters.size(); ++i)
substitutions[fun.parameters[i].name] = &funCall.arguments[i];
_expression = Substitution(substitutions).translate(*boost::get<Assignment>(fun.body.statements.front()).value);
Expression const& arg = funCall.arguments[i];
YulString paraName = fun.parameters[i].name;
// TODO Add metric! This metric should perform well on a pair of functions who
// call each other recursively.
if (!SideEffectsCollector(m_dialect, arg).movable())
return;
size_t refs = ReferencesCounter::countReferences(fun.body)[paraName];
size_t cost = CodeCost::codeCost(m_dialect, arg);
if (refs > 1 && cost > 1)
return;
substitutions[paraName] = &arg;
}
_expression = Substitution(substitutions).translate(*boost::get<Assignment>(fun.body.statements.front()).value);
}
}

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@ -38,7 +38,10 @@ struct Dialect;
* - have a body like r := <functional expression>
* - neither reference themselves nor r in the right hand side
*
* Furthermore, the arguments of the function call cannot have any side-effects.
* Furthermore, for all parameters, all of the following need to be true
* - the argument is movable
* - the parameter is either referenced less than twice in the function body, or the argument is rather cheap
* ("cost" of at most 1 like a constant up to 0xff)
*
* This component can only be used on sources with unique names.
*/
@ -66,5 +69,4 @@ private:
Dialect const& m_dialect;
};
}

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@ -0,0 +1,41 @@
{
// references parameter 1 times in function body
function ref1(a) -> x { x := add(a, 1) }
// references parameter 3 times in function body
function ref3(a) -> x { x := add(a, mul(a, a)) }
let y1 := ref1(calldatasize())
let y2 := ref3(calldatasize())
let y3 := ref1(0xff)
let y4 := ref3(0xff)
let y5 := ref1(0x123)
let y6 := ref3(0x123)
let y7 := ref1(mload(42))
let y8 := ref3(mload(42))
let y9 := ref1(ref3(7))
let y10:= ref3(ref1(7))
let y11:= ref1(y1)
let y12:= ref3(y1)
}
// ====
// step: expressionInliner
// ----
// {
// function ref1(a) -> x
// { x := add(a, 1) }
// function ref3(a_1) -> x_2
// {
// x_2 := add(a_1, mul(a_1, a_1))
// }
// let y1 := add(calldatasize(), 1)
// let y2 := add(calldatasize(), mul(calldatasize(), calldatasize()))
// let y3 := add(0xff, 1)
// let y4 := add(0xff, mul(0xff, 0xff))
// let y5 := add(0x123, 1)
// let y6 := ref3(0x123)
// let y7 := ref1(mload(42))
// let y8 := ref3(mload(42))
// let y9 := add(add(7, mul(7, 7)), 1)
// let y10 := ref3(add(7, 1))
// let y11 := add(y1, 1)
// let y12 := add(y1, mul(y1, y1))
// }