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Fold "FrozenObjectHandle(REF) + CNS" to a byref constant #85888

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merged 7 commits into from
May 9, 2023
Merged

Fold "FrozenObjectHandle(REF) + CNS" to a byref constant #85888

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8bdd54b
Fold "FrozenObjectHandle(REF) + CNS" to a byref constant
EgorBo May 7, 2023
3e57605
Address Single's suggestion
EgorBo May 7, 2023
ee2c656
Generalize it
EgorBo May 7, 2023
153cdbb
fix tests
EgorBo May 7, 2023
41cebff
check opts
EgorBo May 7, 2023
e4d0549
Merge branch 'main' of github.com:dotnet/runtime into fold-frozen-obj…
EgorBo May 8, 2023
9e5e43b
clean up
EgorBo May 8, 2023
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16 changes: 16 additions & 0 deletions src/coreclr/jit/lower.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6247,6 +6247,22 @@ GenTree* Lowering::LowerAdd(GenTreeOp* node)
return next;
}

// Fold ADD(CNS1, CNS2). We mainly target a very specific pattern - byref ADD(frozen_handle, cns_offset)
// We could do this folding earlier, but that is not trivial as we'll have to introduce a way to restore
// the original object from a byref constant for optimizations.
if (comp->opts.OptimizationEnabled() && op1->IsCnsIntOrI() && op2->IsCnsIntOrI() && !node->gtOverflow() &&
(op1->IsIconHandle(GTF_ICON_OBJ_HDL) || op2->IsIconHandle(GTF_ICON_OBJ_HDL)) &&
!op1->AsIntCon()->ImmedValNeedsReloc(comp) && !op2->AsIntCon()->ImmedValNeedsReloc(comp))
{
assert(node->TypeIs(TYP_I_IMPL, TYP_BYREF));

// TODO-CQ: we should allow this for AOT too. For that we need to guarantee that the new constant
// will be lowered as the original handle with offset in a reloc.
BlockRange().Remove(op1);
BlockRange().Remove(op2);
node->BashToConst(op1->AsIntCon()->IconValue() + op2->AsIntCon()->IconValue(), node->TypeGet());
}

#ifdef TARGET_XARCH
if (BlockRange().TryGetUse(node, &use))
{
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