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JIT: Expand recognition of struct field offset pattern #122297

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JIT: Expand recognition of struct field offset pattern #122297

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48 changes: 35 additions & 13 deletions src/coreclr/jit/lclmorph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1142,21 +1142,43 @@ class LocalAddressVisitor final : public GenTreeVisitor<LocalAddressVisitor>
{
Value& rhs = TopValue(0);
Value& lhs = TopValue(1);
if (m_compiler->opts.OptimizationEnabled() && lhs.IsAddress() && rhs.IsAddress() &&
(lhs.LclNum() == rhs.LclNum()) && (rhs.Offset() <= lhs.Offset()) &&
FitsIn<int>(lhs.Offset() - rhs.Offset()))
if (m_compiler->opts.OptimizationEnabled() && lhs.IsAddress() && rhs.IsAddress())
{
// TODO-Bug: Due to inlining we may end up with incorrectly typed SUB trees here.
assert(node->TypeIs(TYP_I_IMPL, TYP_BYREF));
LclVarDsc* lhsDsc = m_compiler->lvaGetDesc(lhs.LclNum());
LclVarDsc* rhsDsc = m_compiler->lvaGetDesc(rhs.LclNum());

ssize_t result = (ssize_t)(lhs.Offset() - rhs.Offset());
node->BashToConst(result, TYP_I_IMPL);
INDEBUG(lhs.Consume());
INDEBUG(rhs.Consume());
PopValue();
PopValue();
m_stmtModified = true;
break;
unsigned lhsLclNum = lhs.LclNum();
unsigned rhsLclNum = rhs.LclNum();

unsigned lhsOffset = lhs.Offset();
unsigned rhsOffset = rhs.Offset();

if (lhsDsc->lvIsStructField)
{
lhsLclNum = lhsDsc->lvParentLcl;
lhsOffset += lhsDsc->lvFldOffset;
}

if (rhsDsc->lvIsStructField)
{
rhsLclNum = rhsDsc->lvParentLcl;
rhsOffset += rhsDsc->lvFldOffset;
}

if ((lhsLclNum == rhsLclNum) && (rhsOffset <= lhsOffset) && FitsIn<int>(lhsOffset - rhsOffset))
{
// TODO-Bug: Due to inlining we may end up with incorrectly typed SUB trees here.
assert(node->TypeIs(TYP_I_IMPL, TYP_BYREF));

ssize_t result = (ssize_t)(lhsOffset - rhsOffset);
node->BashToConst(result, TYP_I_IMPL);
INDEBUG(lhs.Consume());
INDEBUG(rhs.Consume());
PopValue();
PopValue();
m_stmtModified = true;
break;
}
}

EscapeValue(TopValue(0), node);
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