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Merged
EgorBo merged 4 commits into from
Mar 4, 2026
Merged

Improve range analysis for checked bounds in GlobalAP #125056

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1eb00ef
"(uint)normalLclVN < span.Length" means normalLclVN's range is [0..…
Mar 2, 2026
a2152b1
fix a few regressions
Mar 3, 2026
4073e24
Update rangecheck.cpp
EgorBo Mar 3, 2026
e04f59f
Merge branch 'main' into improve-range-analysis
EgorBo Mar 3, 2026
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34 changes: 34 additions & 0 deletions src/coreclr/jit/rangecheck.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1025,6 +1025,40 @@ void RangeCheck::MergeEdgeAssertions(Compiler* comp,
continue;
}
}
// If we're not allowed to emit keBinOpArray, we still can deduce something useful from
// O2K_CHECKED_BOUND_ADD_CNS for never negative checked bounds
//
// Example: "(uint)normalLclVN < span.Length" means normalLclVN's range is [0..INT32_MAX-1]
// Example: "(uint)normalLclVN <= array.Length" means normalLclVN's range is [0..Array.MaxLength]
//
else if (!canUseCheckedBounds && curAssertion.IsRelop() && (curAssertion.GetOp1().GetVN() == normalLclVN) &&
(curAssertion.GetOp2().KindIs(Compiler::O2K_CHECKED_BOUND_ADD_CNS)) &&
(curAssertion.GetOp2().IsCheckedBoundNeverNegative()) &&
(curAssertion.GetOp2().GetCheckedBoundConstant() == 0))
{
// We can assume that the checked bound is within [0..INT32_MAX] thanks to IsCheckedBoundNeverNegative,
// but let's see if we can do better: we could call GetRangeFromAssertions on the checked bound's VN,
// but that may lead to infinite recursion. Also, the checked bound is usually either arr.Length or
// span.Length anyway.
ValueNum checkedBoundVN = curAssertion.GetOp2().GetCheckedBound();

int maxValue = INT32_MAX;
if (comp->vnStore->IsVNArrLen(checkedBoundVN))
{
maxValue = CORINFO_Array_MaxLength;
}
else
{
int cns;
if (comp->vnStore->IsVNIntegralConstant(checkedBoundVN, &cns) && (cns >= 0))
{
maxValue = cns;
}
}

cmpOper = Compiler::AssertionDsc::ToCompareOper(curAssertion.GetKind(), &isUnsigned);
limit = Limit(Limit::keConstant, maxValue);
}
// Current assertion is of the form "i <relop> (checkedBndVN + cns)"
else if (curAssertion.KindIs(Compiler::OAK_GE, Compiler::OAK_GT, Compiler::OAK_LE, Compiler::OAK_LT) &&
curAssertion.GetOp2().KindIs(Compiler::O2K_CHECKED_BOUND_ADD_CNS))
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