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Introduce ceil division helper function.

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This commit is contained in:
chriseth 2021-05-05 10:12:12 +02:00
parent 9d156b52c4
commit 72fc4d4a32
2 changed files with 26 additions and 6 deletions
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25
libsolidity/codegen/YulUtilFunctions.cpp
View File

@ -541,6 +541,18 @@ string YulUtilFunctions::roundUpFunction()
});
}
string YulUtilFunctions::divide32CeilFunction()
{
return m_functionCollector.createFunction(
"divide_by_32_ceil",
[&](vector<string>& _args, vector<string>& _ret) {
_args = {"value"};
_ret = {"result"};
return "result := div(add(value, 31), 32)";
}
);
}
string YulUtilFunctions::overflowCheckedIntAddFunction(IntegerType const& _type)
{
string functionName = "checked_add_" + _type.identifier();
@ -1257,14 +1269,14 @@ string YulUtilFunctions::cleanUpDynamicByteArrayEndSlotsFunction(ArrayType const
return Whiskers(R"(
if gt(len, 31) {
let dataArea := <dataLocation>(array)
let deleteStart := add(dataArea, div(<roundUp>(startIndex), 32))
let deleteStart := add(dataArea, <div32Ceil>(startIndex))
// If we are clearing array to be short byte array, we want to clear only data starting from array data area.
if lt(startIndex, 32) { deleteStart := dataArea }
<clearStorageRange>(deleteStart, add(dataArea, div(add(len, 31), 32)))
<clearStorageRange>(deleteStart, add(dataArea, <div32Ceil>(len)))
}
)")
("dataLocation", arrayDataAreaFunction(_type))
("roundUp", roundUpFunction())
("div32Ceil", divide32CeilFunction())
("clearStorageRange", clearStorageRangeFunction(*_type.baseType()))
.render();
});
@ -1279,13 +1291,13 @@ string YulUtilFunctions::decreaseByteArraySizeFunction(ArrayType const& _type)
switch lt(newLen, 32)
case 0 {
let arrayDataStart := <dataPosition>(array)
let deleteStart := add(arrayDataStart, div(add(newLen, 31), 32))
let deleteStart := add(arrayDataStart, <div32Ceil>(newLen))
// we have to partially clear last slot that is still used
let offset := and(newLen, 0x1f)
if offset { <partialClearStorageSlot>(sub(deleteStart, 1), offset) }
<clearStorageRange>(deleteStart, add(arrayDataStart, div(add(oldLen, 31), 32)))
<clearStorageRange>(deleteStart, add(arrayDataStart, <div32Ceil>(oldLen)))
sstore(array, or(mul(2, newLen), 1))
}
@ -1294,7 +1306,7 @@ string YulUtilFunctions::decreaseByteArraySizeFunction(ArrayType const& _type)
case 1 {
let arrayDataStart := <dataPosition>(array)
// clear whole old array, as we are transforming to short bytes array
<clearStorageRange>(add(arrayDataStart, 1), add(arrayDataStart, div(add(oldLen, 31), 32)))
<clearStorageRange>(add(arrayDataStart, 1), add(arrayDataStart, <div32Ceil>(oldLen)))
<transitLongToShort>(array, newLen)
}
default {
@ -1307,6 +1319,7 @@ string YulUtilFunctions::decreaseByteArraySizeFunction(ArrayType const& _type)
("partialClearStorageSlot", partialClearStorageSlotFunction())
("clearStorageRange", clearStorageRangeFunction(*_type.baseType()))
("transitLongToShort", byteArrayTransitLongToShortFunction(_type))
("div32Ceil", divide32CeilFunction())
("encodeUsedSetLen", shortByteArrayEncodeUsedAreaSetLengthFunction())
.render();
});

7
libsolidity/codegen/YulUtilFunctions.h
View File

@ -126,9 +126,16 @@ public:
/// @returns the name of a function that rounds its input to the next multiple
/// of 32 or the input if it is a multiple of 32.
/// Ignores overflow.
/// signature: (value) -> result
std::string roundUpFunction();
/// @returns the name of a function that divides by 32 and rounds up during the division.
/// In other words, on input x it returns the smallest y such that y * 32 >= x.
/// Ignores overflow.
/// signature: (x) -> y
std::string divide32CeilFunction();
/// signature: (x, y) -> sum
std::string overflowCheckedIntAddFunction(IntegerType const& _type);
/// signature: (x, y) -> sum