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SSA: Remove unnecessary shuffling logic #16591

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Merged
blishko merged 1 commit into from
Apr 13, 2026
+1 −36
Merged

SSA: Remove unnecessary shuffling logic #16591

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37 changes: 1 addition & 36 deletions libyul/backends/evm/ssa/StackShuffler.h
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Original file line number Diff line number Diff line change
Expand Up @@ -415,42 +415,7 @@ class StackShuffler
// if the stack top isn't where it likes to be right now, try to put it somewhere more sensible
if (!_state.isArgsCompatible(stackTop, stackTop))
{
// if the stack top should go into the tail but isn't there yet and we have enough of it in args
if (
_state.requiredInTail(_stack[stackTop]) &&
_state.countInTail(_stack[stackTop]) == 0 &&
_state.countInArgs(_stack[stackTop]) > _state.targetArgsCount(_stack[stackTop])
)
{
// try swapping it with something in the tail that also fixes the top
for (StackOffset offset: _state.stackTailRange())
if (_stack.isValidSwapTarget(offset) && _state.isArgsCompatible(offset, stackTop))
{
_stack.swap(offset);
return {ShuffleHelperResult::Status::StackModified};
}
// otherwise try swapping it with something that needs to go into args
for (StackOffset offset: _state.stackTailRange())
if (_stack.isValidSwapTarget(offset) && _state.countInArgs(_stack[offset]) < _state.targetArgsCount(_stack[offset]))
{
_stack.swap(offset);
return {ShuffleHelperResult::Status::StackModified};
}
// otherwise try swapping it with something that can be popped
for (StackOffset offset: _state.stackTailRange())
if (_stack.isValidSwapTarget(offset) && _stack.canBeFreelyGenerated(_stack[offset]) && !_stack[offset].isLiteralValueID())
{
_stack.swap(offset);
return {ShuffleHelperResult::Status::StackModified};
}
// otherwise try swapping it with a literal
for (StackOffset offset: _state.stackTailRange())
if (_stack.isValidSwapTarget(offset) && _stack[offset].isLiteralValueID())
{
_stack.swap(offset);
return {ShuffleHelperResult::Status::StackModified};
}
}
yulAssert(!_state.requiredInTail(_stack[stackTop]) || _state.countInTail(_stack[stackTop]) > 0);
// try finding a slot that is compatible with the top and also admits the current top:
// - could be that the top slot is used elsewhere in the args (exclude junk)
// - could be that the top slot is something that is only required in the tail
Expand Down