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Report stack too deep and conditionally aggressively compress stack in StackLayoutGenerator.

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This commit is contained in:
Daniel Kirchner
2021-09-06 09:08:04 +02:00
parent 8447b32d52
commit e022ba1bfb
3 changed files with 168 additions and 16 deletions
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libyul/backends/evm/StackLayoutGenerator.h
+22 -2
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@@ -47,7 +47,23 @@ struct StackLayout
class StackLayoutGenerator
{
public:
struct StackTooDeep
{
/// Number of slots that need to be saved.
size_t deficit = 0;
/// Set of variables, eliminating which would decrease the stack deficit.
std::vector<YulString> variableChoices;
};
static StackLayout run(CFG const& _cfg);
/// @returns a map from function names to the stack too deep errors occurring in that function.
/// Requires @a _cfg to be a control flow graph generated from disambiguated Yul.
/// The empty string is mapped to the stack too deep errors of the main entry point.
static std::map<YulString, std::vector<StackTooDeep>> reportStackTooDeep(CFG const& _cfg);
/// @returns all stack too deep errors in the function named @a _functionName.
/// Requires @a _cfg to be a control flow graph generated from disambiguated Yul.
/// If @a _functionName is empty, the stack too deep errors of the main entry point are reported instead.
static std::vector<StackTooDeep> reportStackTooDeep(CFG const& _cfg, YulString _functionName);
private:
StackLayoutGenerator(StackLayout& _context);
@@ -55,11 +71,11 @@ private:
/// @returns the optimal entry stack layout, s.t. @a _operation can be applied to it and
/// the result can be transformed to @a _exitStack with minimal stack shuffling.
/// Simultaneously stores the entry layout required for executing the operation in m_layout.
Stack propagateStackThroughOperation(Stack _exitStack, CFG::Operation const& _operation);
Stack propagateStackThroughOperation(Stack _exitStack, CFG::Operation const& _operation, bool _aggressiveStackCompression = false);
/// @returns the desired stack layout at the entry of @a _block, assuming the layout after
/// executing the block should be @a _exitStack.
Stack propagateStackThroughBlock(Stack _exitStack, CFG::BasicBlock const& _block);
Stack propagateStackThroughBlock(Stack _exitStack, CFG::BasicBlock const& _block, bool _aggressiveStackCompression = false);
/// Main algorithm walking the graph from entry to exit and propagating back the stack layouts to the entries.
/// Iteratively reruns itself along backwards jumps until the layout is stabilized.
@@ -86,6 +102,10 @@ private:
/// stack shuffling when starting from the returned layout.
static Stack combineStack(Stack const& _stack1, Stack const& _stack2);
/// Walks through the CFG and reports any stack too deep errors that would occur when generating code for it
/// without countermeasures.
std::vector<StackTooDeep> reportStackTooDeep(CFG::BasicBlock const& _entry) const;
/// @returns a copy of @a _stack stripped of all duplicates and slots that can be freely generated.
/// Attempts to create a layout that requires a minimal amount of operations to reconstruct the original
/// stack @a _stack.