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merged 4 commits into from
May 28, 2022
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Optimize better with maximum array length #69735

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b017a47
Optimize better with maximum array length
BruceForstall May 24, 2022
7f8967f
Use CORINFO_Array_MaxLength
BruceForstall May 25, 2022
99ccec0
Consider both Span and array for bounds check limit
BruceForstall May 27, 2022
eabc989
Formatting
BruceForstall May 27, 2022
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23 changes: 18 additions & 5 deletions src/coreclr/jit/assertionprop.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -39,13 +39,26 @@ bool IntegralRange::Contains(int64_t value) const
// value - the symbolic value in question
//
// Return Value:
// Integer correspoding to the symbolic value.
// Integer corresponding to the symbolic value.
//
/* static */ int64_t IntegralRange::SymbolicToRealValue(SymbolicIntegerValue value)
{
static const int64_t SymbolicToRealMap[]{INT64_MIN, INT32_MIN, INT16_MIN, INT8_MIN, 0,
1, INT8_MAX, UINT8_MAX, INT16_MAX, UINT16_MAX,
INT32_MAX, UINT32_MAX, INT64_MAX};
static const int64_t SymbolicToRealMap[]{
INT64_MIN, // SymbolicIntegerValue::LongMin
INT32_MIN, // SymbolicIntegerValue::IntMin
INT16_MIN, // SymbolicIntegerValue::ShortMin
INT8_MIN, // SymbolicIntegerValue::ByteMin
0, // SymbolicIntegerValue::Zero
1, // SymbolicIntegerValue::One
INT8_MAX, // SymbolicIntegerValue::ByteMax
UINT8_MAX, // SymbolicIntegerValue::UByteMax
INT16_MAX, // SymbolicIntegerValue::ShortMax
UINT16_MAX, // SymbolicIntegerValue::UShortMax
CORINFO_Array_MaxLength, // SymbolicIntegerValue::ArrayLenMax
INT32_MAX, // SymbolicIntegerValue::IntMax
UINT32_MAX, // SymbolicIntegerValue::UIntMax
INT64_MAX // SymbolicIntegerValue::LongMax
};

assert(sizeof(SymbolicIntegerValue) == sizeof(int32_t));
assert(SymbolicToRealMap[static_cast<int32_t>(SymbolicIntegerValue::LongMin)] == INT64_MIN);
Expand Down Expand Up @@ -145,7 +158,7 @@ bool IntegralRange::Contains(int64_t value) const
return {SymbolicIntegerValue::Zero, SymbolicIntegerValue::One};

case GT_ARR_LENGTH:
return {SymbolicIntegerValue::Zero, SymbolicIntegerValue::IntMax};
return {SymbolicIntegerValue::Zero, SymbolicIntegerValue::ArrayLenMax};

case GT_CALL:
if (node->AsCall()->NormalizesSmallTypesOnReturn())
Expand Down
1 change: 1 addition & 0 deletions src/coreclr/jit/compiler.h
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Expand Up @@ -1181,6 +1181,7 @@ enum class SymbolicIntegerValue : int32_t
UByteMax,
ShortMax,
UShortMax,
ArrayLenMax,
IntMax,
UIntMax,
LongMax,
Expand Down
24 changes: 16 additions & 8 deletions src/coreclr/jit/rangecheck.cpp
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Expand Up @@ -1056,13 +1056,7 @@ Range RangeCheck::ComputeRangeForLocalDef(BasicBlock* block,
return range;
}

// https://msdn.microsoft.com/en-us/windows/apps/hh285054.aspx
// CLR throws IDS_EE_ARRAY_DIMENSIONS_EXCEEDED if array length is > INT_MAX.
// new byte[INT_MAX]; still throws OutOfMemoryException on my system with 32 GB RAM.
// I believe practical limits are still smaller than this number.
#define ARRLEN_MAX (0x7FFFFFFF)

// Get the limit's maximum possible value, treating array length to be ARRLEN_MAX.
// Get the limit's maximum possible value.
bool RangeCheck::GetLimitMax(Limit& limit, int* pMax)
{
int& max1 = *pMax;
Expand All @@ -1077,7 +1071,21 @@ bool RangeCheck::GetLimitMax(Limit& limit, int* pMax)
int tmp = GetArrLength(limit.vn);
if (tmp <= 0)
{
tmp = ARRLEN_MAX;
// If we can't figure out the array length, use the maximum array length,
// CORINFO_Array_MaxLength (0x7FFFFFC7). However, we get here also when
// we can't find a Span/ReadOnlySpan bounds check length, and these have
// a maximum length of INT_MAX (0x7FFFFFFF). If limit.vn refers to a
// GT_ARR_LENGTH node, then it's an array length, otherwise use the INT_MAX value.

if (m_pCompiler->vnStore->IsVNArrLen(limit.vn))
{
tmp = CORINFO_Array_MaxLength;
}
else
{
const int MaxSpanLength = 0x7FFFFFFF;
tmp = MaxSpanLength;
}
}
if (IntAddOverflows(tmp, limit.GetConstant()))
{
Expand Down
4 changes: 2 additions & 2 deletions src/coreclr/jit/rangecheck.h
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Expand Up @@ -581,8 +581,8 @@ class RangeCheck
// Inspect the assertions about the current ValueNum to refine pRange
void MergeEdgeAssertions(ValueNum num, ASSERT_VALARG_TP assertions, Range* pRange);

// The maximum possible value of the given "limit." If such a value could not be determined
// return "false." For example: ARRLEN_MAX for array length.
// The maximum possible value of the given "limit". If such a value could not be determined
// return "false". For example: CORINFO_Array_MaxLength for array length.
bool GetLimitMax(Limit& limit, int* pMax);

// Does the addition of the two limits overflow?
Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/jit/valuenum.cpp
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Expand Up @@ -5749,7 +5749,7 @@ bool ValueNumStore::IsVNCheckedBound(ValueNum vn)
if (m_checkedBoundVNs.TryGetValue(vn, &dummy))
{
// This VN appeared as the conservative VN of the length argument of some
// GT_ARR_BOUND node.
// GT_BOUNDS_CHECK node.
return true;
}
if (IsVNArrLen(vn))
Expand Down