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Add upper bound for computing constants.

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This commit is contained in:
chriseth 2017-03-03 16:17:21 +01:00
parent 05dac99922
commit ddc4918f36
2 changed files with 5 additions and 1 deletions
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4
libevmasm/ConstantOptimiser.cpp
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@ -194,7 +194,7 @@ AssemblyItems ComputeMethod::findRepresentation(u256 const& _value)
// Is not always better, try literal and decomposition method.
AssemblyItems routine{u256(_value)};
bigint bestGas = gasNeeded(routine);
for (unsigned bits = 255; bits > 8; --bits)
for (unsigned bits = 255; bits > 8 && m_maxSteps > 0; --bits)
{
unsigned gapDetector = unsigned(_value >> (bits - 8)) & 0x1ff;
if (gapDetector != 0xff && gapDetector != 0x100)
@ -219,6 +219,8 @@ AssemblyItems ComputeMethod::findRepresentation(u256 const& _value)
else if (lowerPart < 0)
newRoutine.push_back(Instruction::SUB);
if (m_maxSteps > 0)
m_maxSteps--;
bigint newGas = gasNeeded(newRoutine);
if (newGas < bestGas)
{

2
libevmasm/ConstantOptimiser.h
View File

@ -143,6 +143,8 @@ protected:
AssemblyItems findRepresentation(u256 const& _value);
bigint gasNeeded(AssemblyItems const& _routine);
/// Counter for the complexity of optimization, will stop when it reaches zero.
size_t m_maxSteps = 10000;
AssemblyItems m_routine;
};