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JIT: Cleanup redundant local address exposure in RewriteUses #90727

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JIT: Cleanup redundant local address exposure in RewriteUses #90727

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d5fac54
Cleanup redundant stack local addr exposure in RewriteUses
hez2010 Aug 17, 2023
a9795f7
Fix format
hez2010 Aug 17, 2023
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102 changes: 99 additions & 3 deletions src/coreclr/jit/objectalloc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -756,6 +756,7 @@ void ObjectAllocator::RewriteUses()
class RewriteUsesVisitor final : public GenTreeVisitor<RewriteUsesVisitor>
{
ObjectAllocator* m_allocator;
LocalToLocalMap* m_varSet;

public:
enum
Expand All @@ -765,8 +766,8 @@ void ObjectAllocator::RewriteUses()
ComputeStack = true,
};

RewriteUsesVisitor(ObjectAllocator* allocator)
: GenTreeVisitor<RewriteUsesVisitor>(allocator->comp), m_allocator(allocator)
RewriteUsesVisitor(ObjectAllocator* allocator, LocalToLocalMap* varSet)
: GenTreeVisitor<RewriteUsesVisitor>(allocator->comp), m_allocator(allocator), m_varSet(varSet)
{
}

Expand All @@ -792,6 +793,7 @@ void ObjectAllocator::RewriteUses()
newType = TYP_I_IMPL;
tree = m_compiler->gtNewLclVarAddrNode(newLclNum);
*use = tree;
m_varSet->AddOrUpdate(newLclNum, lclNum);
}
else
{
Expand All @@ -815,12 +817,106 @@ void ObjectAllocator::RewriteUses()
}
};

class RemoveAddrLclVisitor final : public GenTreeVisitor<RemoveAddrLclVisitor>
{
ObjectAllocator* m_allocator;
LocalToLocalMap* m_varSet;
LocalToLclOffMap* m_varUpdateSet;
BasicBlock* m_block;
Statement* m_stmt;

public:
enum
{
DoPreOrder = true,
DoLclVarsOnly = true,
ComputeStack = true,
};

RemoveAddrLclVisitor(ObjectAllocator* allocator,
LocalToLocalMap* varSet,
LocalToLclOffMap* varUpdateSet,
BasicBlock* block,
Statement* stmt)
: GenTreeVisitor<RemoveAddrLclVisitor>(allocator->comp)
, m_allocator(allocator)
, m_varSet(varSet)
, m_varUpdateSet(varUpdateSet)
, m_block(block)
, m_stmt(stmt)
{
}

Compiler::fgWalkResult PreOrderVisit(GenTree** use, GenTree* user)
{
GenTree* tree = *use;
assert(tree->OperIsAnyLocal());

const unsigned int lclNum = tree->AsLclVarCommon()->GetLclNum();
unsigned int oldLclNum;
LclVarDsc* lclVarDsc;

if (m_varSet->TryGetValue(lclNum, &oldLclNum))
{
lclVarDsc = m_compiler->lvaGetDesc(oldLclNum);
}
else
{
oldLclNum = lclNum;
lclVarDsc = m_compiler->lvaGetDesc(lclNum);
}

if ((oldLclNum < BitVecTraits::GetSize(&m_allocator->m_bitVecTraits)) &&
m_allocator->MayLclVarPointToStack(oldLclNum))
{
if (tree->OperIsLocalStore())
{
GenTree* data = tree->Data();
if (data->OperIs(GT_LCL_ADDR) &&
!m_compiler->optIsVarAssigned(m_block, m_compiler->fgLastBB, tree, lclNum))
{
unsigned long long lclNumAndOff = data->AsLclVarCommon()->GetLclNum();
lclNumAndOff = (lclNumAndOff << 16) | data->AsLclVarCommon()->GetLclOffs();
m_varUpdateSet->AddOrUpdate(lclNum, lclNumAndOff);
m_compiler->fgRemoveStmt(m_block, m_stmt);
return Compiler::fgWalkResult::WALK_ABORT;
}
}
}

unsigned long long newLclNumAndOff;
if (m_varUpdateSet->TryGetValue(lclNum, &newLclNumAndOff))
{
uint16_t newLclOff = (uint16_t)(newLclNumAndOff & 0xFFFF);
unsigned int newLclNum = (unsigned int)(newLclNumAndOff >> 16);
tree->ReplaceWith(m_compiler->gtNewLclAddrNode(newLclNum, newLclOff), m_compiler);
}

return Compiler::fgWalkResult::WALK_CONTINUE;
}
};

LocalToLocalMap* localMap =
new (comp->getAllocator(CMK_ObjectAllocator)) LocalToLocalMap(comp->getAllocator(CMK_ObjectAllocator));

for (BasicBlock* const block : comp->Blocks())
{
for (Statement* const stmt : block->Statements())
{
RewriteUsesVisitor rewriteUsesVisitor(this);
RewriteUsesVisitor rewriteUsesVisitor(this, localMap);
rewriteUsesVisitor.WalkTree(stmt->GetRootNodePointer(), nullptr);
}
}

LocalToLclOffMap* updateMap =
new (comp->getAllocator(CMK_ObjectAllocator)) LocalToLclOffMap(comp->getAllocator(CMK_ObjectAllocator));

for (BasicBlock* const block : comp->Blocks())
{
for (Statement* const stmt : block->Statements())
{
RemoveAddrLclVisitor removeAddrLclVisitor(this, localMap, updateMap, block, stmt);
removeAddrLclVisitor.WalkTree(stmt->GetRootNodePointer(), nullptr);
}
}
}
3 changes: 2 additions & 1 deletion src/coreclr/jit/objectalloc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,8 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

class ObjectAllocator final : public Phase
{
typedef SmallHashTable<unsigned int, unsigned int, 8U> LocalToLocalMap;
typedef SmallHashTable<unsigned int, unsigned int, 8U> LocalToLocalMap;
typedef SmallHashTable<unsigned int, unsigned long long, 8U> LocalToLclOffMap;

//===============================================================================
// Data members
Expand Down
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