cerc-io/solidity
11
0
Fork 0
mirror of https://github.com/ethereum/solidity synced 2023-10-03 13:03:40 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Improved stack shuffling in corner cases.

Browse Source
This commit is contained in:
Daniel Kirchner
2022-01-21 15:41:30 +01:00
parent 76540b338e
commit de28f31716
4 changed files with 92 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
libyul/backends/evm/StackHelpers.h
+36 -1
View File
@@ -262,6 +262,11 @@ private:
if (ops.sourceMultiplicity(ops.sourceSize() - 1 - swapDepth) < 0)
{
ops.swap(swapDepth);
if (ops.targetIsArbitrary(sourceTop))
// Usually we keep a slot that is to-be-removed, if the current top is arbitrary.
// However, since we are in a stack-too-deep situation, pop it immediately
// to compress the stack (we can always push back junk in the end).
ops.pop();
return true;
}
// Otherwise we rely on stack compression or stack-to-memory.
@@ -321,14 +326,44 @@ private:
yulAssert(ops.sourceMultiplicity(i) == 0 && (ops.targetIsArbitrary(i) || ops.targetMultiplicity(i) == 0), "");
yulAssert(ops.isCompatible(sourceTop, sourceTop), "");
auto swappableOffsets = ranges::views::iota(size > 17 ? size - 17 : 0u, size);
// If we find a lower slot that is out of position, but also compatible with the top, swap that up.
for (size_t offset: swappableOffsets)
if (!ops.isCompatible(offset, offset) && ops.isCompatible(sourceTop, offset))
{
ops.swap(size - offset - 1);
return true;
}
// Swap up any reachable slot that is still out of position.
for (size_t offset: swappableOffsets)
if (!ops.isCompatible(offset, offset) && !ops.sourceIsSame(offset, sourceTop))
{
ops.swap(size - offset - 1);
return true;
}
// We are in a stack-too-deep situation and try to reduce the stack size.
// If the current top is merely kept since the target slot is arbitrary, pop it.
if (ops.targetIsArbitrary(sourceTop) && ops.sourceMultiplicity(sourceTop) <= 0)
{
ops.pop();
return true;
}
// If any reachable slot is merely kept, since the target slot is arbitrary, swap it up and pop it.
for (size_t offset: swappableOffsets)
if (ops.targetIsArbitrary(offset) && ops.sourceMultiplicity(offset) <= 0)
{
ops.swap(size - offset - 1);
ops.pop();
return true;
}
// We cannot avoid a stack-too-deep error. Repeat the above without restricting to reachable slots.
for (size_t offset: ranges::views::iota(0u, size))
if (!ops.isCompatible(offset, offset) && ops.isCompatible(sourceTop, offset))
{
ops.swap(size - offset - 1);
return true;
}
// Swap up any slot that is still out of position.
for (size_t offset: ranges::views::iota(0u, size))
if (!ops.isCompatible(offset, offset) && !ops.sourceIsSame(offset, sourceTop))
{