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Improve handling of VNF_Cast in GetRangeFromAssertionsWorker #128923

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Improve handling of VNF_Cast in GetRangeFromAssertionsWorker #128923

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47 changes: 35 additions & 12 deletions src/coreclr/jit/rangecheck.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -728,21 +728,44 @@ Range RangeCheck::GetRangeFromAssertionsWorker(
bool srcIsUnsigned;
comp->vnStore->GetCastOperFromVN(funcApp.GetArg(1), &castToType, &srcIsUnsigned);

// GetRangeFromType returns a non-constant range if it can't be represented with Range
Range castToTypeRange = GetRangeFromType(castToType);
if (castToTypeRange.IsConstantRange())
ValueNum arg0VN = funcApp.GetArg(0);
var_types arg0Typ = comp->vnStore->TypeOfVN(arg0VN);

var_types castFromType = srcIsUnsigned ? varTypeToUnsigned(arg0Typ) : arg0Typ;

if (genTypeSize(castFromType) < genTypeSize(castToType))
{
result = castToTypeRange;
// We're going from a small type to a large type
// and so regardless of whether we zero or sign-extend
// the value is preserved within the confines of its
// original input for the destination, i.e. it always
// passes the FitsIn<fromType> check.

// Now see if we can do better by looking at the cast source.
// if its range is within the castTo range, we can use that (and the cast is basically a no-op).
if (genActualType(comp->vnStore->TypeOfVN(funcApp.GetArg(0))) == TYP_INT)
result = GetRangeFromType(castFromType);
}
else
{
// We're either going from a big type to a small type
// or between signed and unsigned types of the same size
// so we want to use toType as the range.

result = GetRangeFromType((castToType == TYP_UINT) ? TYP_INT : castToType);
}

// Now see if we can do better by looking at the cast source.
// if its range is within the castTo range, we can use that (and the cast is basically a no-op).
if (genActualType(arg0Typ) == TYP_INT)
{
Range castOpRange = GetRangeFromAssertionsWorker(comp, arg0VN, assertions, --budget, visited);

if (castOpRange.IsConstantRange())
{
Range castOpRange =
GetRangeFromAssertionsWorker(comp, funcApp.GetArg(0), assertions, --budget, visited);
if (castOpRange.IsConstantRange() &&
(castOpRange.LowerLimit().GetConstant() >= castToTypeRange.LowerLimit().GetConstant()) &&
(castOpRange.UpperLimit().GetConstant() <= castToTypeRange.UpperLimit().GetConstant()))
if (!result.IsConstantRange())
{
result = castOpRange;
}
else if ((castOpRange.LowerLimit().GetConstant() >= result.LowerLimit().GetConstant()) &&
(castOpRange.UpperLimit().GetConstant() <= result.UpperLimit().GetConstant()))
{
result = castOpRange;
}
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