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Fix Redundant bound check for span.Length == 0 pattern #101323

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merged 3 commits into from
Apr 22, 2024
Merged

Fix Redundant bound check for span.Length == 0 pattern #101323

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328ecf6
Fix Redundant bound check for span.Length == 0 pattern
EgorBo Apr 20, 2024
825f554
Fix regressions
EgorBo Apr 20, 2024
0ab503c
Formatting
EgorBo Apr 20, 2024
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33 changes: 30 additions & 3 deletions src/coreclr/jit/rangecheck.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -866,10 +866,37 @@ void RangeCheck::MergeEdgeAssertions(ValueNum normalLclVN, ASSERT_VALARG_TP asse
continue;
}

// Doesn't tighten the current bound. So skip.
if (pRange->uLimit.IsConstant() && limit.vn != arrLenVN)
// Skip if it doesn't tighten the current bound:
if (pRange->uLimit.IsConstant() && ((cmpOper == GT_LE) || (cmpOper == GT_LT)))
{
continue;
if (!limit.IsConstant() && (limit.vn != arrLenVN))
{
// If our new limit is not constant and doesn't represent the array's length - bail out.
// NOTE: it's fine to replace the current constant limit with a non-constant arrLenVN.
continue;
}
if (limit.IsConstant() && (limit.cns > pRange->uLimit.cns))
{
// The new constant limit doesn't tighten the current constant bound.
// E.g. current is "X < 10" and the new one is "X < 100"
continue;
}
}
// Same for the lower bound:
if (pRange->lLimit.IsConstant() && ((cmpOper == GT_GE) || (cmpOper == GT_GT)))
{
if (!limit.IsConstant() && (limit.vn != arrLenVN))
{
// If our new limit is not constant and doesn't represent the array's length - bail out.
// NOTE: it's fine to replace the current constant limit with a non-constant arrLenVN.
continue;
}
if (limit.IsConstant() && (limit.cns < pRange->lLimit.cns))
{
// The new constant limit doesn't tighten the current constant bound.
// E.g. current is "X > 10" and the new one is "X > 5"
continue;
}
}

// Check if the incoming limit from assertions tightens the existing upper limit.
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