// Check if the computed range is within bounds.
bool RangeCheck::BetweenBounds(Range& range, int lower, GenTreePtr upper)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("%s BetweenBounds <%d, ", range.ToString(m_pCompiler->getAllocatorDebugOnly()), lower);
Compiler::printTreeID(upper);
printf(">\n");
}
#endif // DEBUG
// Get the VN for the upper limit.
ValueNum uLimitVN = upper->gtVNPair.GetConservative();
#ifdef DEBUG
JITDUMP("VN%04X upper bound is: ", uLimitVN);
if (m_pCompiler->verbose)
{
m_pCompiler->vnStore->vnDump(m_pCompiler, uLimitVN);
}
JITDUMP("\n");
#endif
// If the upper limit is not length, then bail.
if (!m_pCompiler->vnStore->IsVNArrLen(uLimitVN))
{
return false;
}
// Get the array reference from the length.
ValueNum arrRefVN = m_pCompiler->vnStore->GetArrForLenVn(uLimitVN);
#ifdef DEBUG
JITDUMP("Array ref VN");
if (m_pCompiler->verbose)
{
m_pCompiler->vnStore->vnDump(m_pCompiler, arrRefVN);
}
JITDUMP("\n");
#endif
// Check if array size can be obtained.
int arrSize = m_pCompiler->vnStore->GetNewArrSize(arrRefVN);
JITDUMP("Array size is: %d\n", arrSize);
// Upper limit: a.len + ucns (upper limit constant).
if (range.UpperLimit().IsBinOpArray())
{
if (range.UpperLimit().vn != arrRefVN)
{
return false;
}
int ucns = range.UpperLimit().GetConstant();
// Upper limit: a.Len + [0..n]
if (ucns >= 0)
{
return false;
}
// If lower limit is a.len return false.
if (range.LowerLimit().IsArray())
{
return false;
}
// Since upper limit is bounded by the array, return true if lower bound is good.
// TODO-CQ: I am retaining previous behavior to minimize ASM diffs, but we could
// return "true" here if GetConstant() >= 0 instead of "== 0".
if (range.LowerLimit().IsConstant() && range.LowerLimit().GetConstant() == 0)
{
return true;
}
// Check if we have the array size allocated by new.
if (arrSize <= 0)
{
return false;
}
// At this point,
// upper limit = a.len + ucns. ucns < 0
// lower limit = a.len + lcns.
if (range.LowerLimit().IsBinOpArray())
{
int lcns = range.LowerLimit().GetConstant();
if (lcns >= 0 || -lcns > arrSize)
{
return false;
}
return (range.LowerLimit().vn == arrRefVN && lcns <= ucns);
}
}
// If upper limit is constant
else if (range.UpperLimit().IsConstant())
{
if (arrSize <= 0)
{
return false;
}
int ucns = range.UpperLimit().GetConstant();
if (ucns >= arrSize)
{
return false;
}
if (range.LowerLimit().IsConstant())
{
int lcns = range.LowerLimit().GetConstant();
// Make sure lcns < ucns which is already less than arrSize.
return (lcns >= 0 && lcns <= ucns);
}
if (range.LowerLimit().IsBinOpArray())
{
int lcns = range.LowerLimit().GetConstant();
// a.len + lcns, make sure we don't subtract too much from a.len.
if (lcns >= 0 || -lcns > arrSize)
{
return false;
}
// Make sure a.len + lcns <= ucns.
return (range.LowerLimit().vn == arrRefVN && (arrSize + lcns) <= ucns);
}
}
return false;
}
// Check if the computed range is within bounds.
bool RangeCheck::BetweenBounds(Range& range, int lower, GenTree* upper)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("%s BetweenBounds <%d, ", range.ToString(m_pCompiler->getAllocatorDebugOnly()), lower);
Compiler::printTreeID(upper);
printf(">\n");
}
#endif // DEBUG
ValueNumStore* vnStore = m_pCompiler->vnStore;
// Get the VN for the upper limit.
ValueNum uLimitVN = vnStore->VNConservativeNormalValue(upper->gtVNPair);
#ifdef DEBUG
JITDUMP(FMT_VN " upper bound is: ", uLimitVN);
if (m_pCompiler->verbose)
{
vnStore->vnDump(m_pCompiler, uLimitVN);
}
JITDUMP("\n");
#endif
int arrSize = 0;
if (vnStore->IsVNConstant(uLimitVN))
{
ssize_t constVal = -1;
unsigned iconFlags = 0;
if (m_pCompiler->optIsTreeKnownIntValue(true, upper, &constVal, &iconFlags))
{
arrSize = (int)constVal;
}
}
else if (vnStore->IsVNArrLen(uLimitVN))
{
// Get the array reference from the length.
ValueNum arrRefVN = vnStore->GetArrForLenVn(uLimitVN);
// Check if array size can be obtained.
arrSize = vnStore->GetNewArrSize(arrRefVN);
}
else if (!vnStore->IsVNCheckedBound(uLimitVN))
{
// If the upper limit is not length, then bail.
return false;
}
JITDUMP("Array size is: %d\n", arrSize);
// Upper limit: len + ucns (upper limit constant).
if (range.UpperLimit().IsBinOpArray())
{
if (range.UpperLimit().vn != uLimitVN)
{
return false;
}
int ucns = range.UpperLimit().GetConstant();
// Upper limit: Len + [0..n]
if (ucns >= 0)
{
return false;
}
// Since upper limit is bounded by the array, return true if lower bound is good.
if (range.LowerLimit().IsConstant() && range.LowerLimit().GetConstant() >= 0)
{
return true;
}
// Check if we have the array size allocated by new.
if (arrSize <= 0)
{
return false;
}
// At this point,
// upper limit = len + ucns. ucns < 0
// lower limit = len + lcns.
if (range.LowerLimit().IsBinOpArray())
{
int lcns = range.LowerLimit().GetConstant();
if (lcns >= 0 || -lcns > arrSize)
{
return false;
}
return (range.LowerLimit().vn == uLimitVN && lcns <= ucns);
}
}
// If upper limit is constant
else if (range.UpperLimit().IsConstant())
{
if (arrSize <= 0)
{
return false;
}
int ucns = range.UpperLimit().GetConstant();
if (ucns >= arrSize)
{
return false;
}
if (range.LowerLimit().IsConstant())
{
int lcns = range.LowerLimit().GetConstant();
// Make sure lcns < ucns which is already less than arrSize.
return (lcns >= 0 && lcns <= ucns);
}
if (range.LowerLimit().IsBinOpArray())
{
int lcns = range.LowerLimit().GetConstant();
// len + lcns, make sure we don't subtract too much from len.
if (lcns >= 0 || -lcns > arrSize)
{
return false;
}
// Make sure a.len + lcns <= ucns.
return (range.LowerLimit().vn == uLimitVN && (arrSize + lcns) <= ucns);
}
}
return false;
}
void RangeCheck::OptimizeRangeCheck(BasicBlock* block, GenTreePtr stmt, GenTreePtr treeParent)
{
// Check if we are dealing with a bounds check node.
if (treeParent->OperGet() != GT_COMMA)
{
return;
}
// If we are not looking at array bounds check, bail.
GenTreePtr tree = treeParent->gtOp.gtOp1;
if (tree->gtOper != GT_ARR_BOUNDS_CHECK)
{
return;
}
GenTreeBoundsChk* bndsChk = tree->AsBoundsChk();
m_pCurBndsChk = bndsChk;
GenTreePtr treeIndex = bndsChk->gtIndex;
// Take care of constant index first, like a[2], for example.
ValueNum idxVn = treeIndex->gtVNPair.GetConservative();
ValueNum arrLenVn = bndsChk->gtArrLen->gtVNPair.GetConservative();
int arrSize = GetArrLength(arrLenVn);
JITDUMP("ArrSize for lengthVN:%03X = %d\n", arrLenVn, arrSize);
if (m_pCompiler->vnStore->IsVNConstant(idxVn) && arrSize > 0)
{
ssize_t idxVal = -1;
unsigned iconFlags = 0;
if (!m_pCompiler->optIsTreeKnownIntValue(true, treeIndex, &idxVal, &iconFlags))
{
return;
}
JITDUMP("[RangeCheck::OptimizeRangeCheck] Is index %d in <0, arrLenVn VN%X sz:%d>.\n", idxVal, arrLenVn, arrSize);
if (arrSize > 0 && idxVal < arrSize && idxVal >= 0)
{
JITDUMP("Removing range check\n");
m_pCompiler->optRemoveRangeCheck(treeParent, stmt, true, GTF_ASG, true /* force remove */);
return;
}
}
GetRangeMap()->RemoveAll();
GetOverflowMap()->RemoveAll();
// Get the range for this index.
SearchPath* path = new (m_pCompiler->getAllocator()) SearchPath(m_pCompiler->getAllocator());
Range range = GetRange(block, stmt, treeIndex, path, false DEBUGARG(0));
// If upper or lower limit is found to be unknown (top), or it was found to
// be unknown because of over budget or a deep search, then return early.
if (range.UpperLimit().IsUnknown() || range.LowerLimit().IsUnknown())
{
// Note: If we had stack depth too deep in the GetRange call, we'd be
// too deep even in the DoesOverflow call. So return early.
return;
}
if (DoesOverflow(block, stmt, treeIndex, path))
{
JITDUMP("Method determined to overflow.\n");
return;
}
JITDUMP("Range value %s\n", range.ToString(m_pCompiler->getAllocatorDebugOnly()));
path->RemoveAll();
Widen(block, stmt, treeIndex, path, &range);
// If upper or lower limit is unknown, then return.
if (range.UpperLimit().IsUnknown() || range.LowerLimit().IsUnknown())
{
return;
}
// Is the range between the lower and upper bound values.
if (BetweenBounds(range, 0, bndsChk->gtArrLen))
{
JITDUMP("[RangeCheck::OptimizeRangeCheck] Between bounds\n");
m_pCompiler->optRemoveRangeCheck(treeParent, stmt, true, GTF_ASG, true /* force remove */);
}
return;
}
void RangeCheck::OptimizeRangeCheck(BasicBlock* block, GenTreeStmt* stmt, GenTree* treeParent)
{
// Check if we are dealing with a bounds check node.
if (treeParent->OperGet() != GT_COMMA)
{
return;
}
// If we are not looking at array bounds check, bail.
GenTree* tree = treeParent->gtOp.gtOp1;
if (!tree->OperIsBoundsCheck())
{
return;
}
GenTreeBoundsChk* bndsChk = tree->AsBoundsChk();
m_pCurBndsChk = bndsChk;
GenTree* treeIndex = bndsChk->gtIndex;
// Take care of constant index first, like a[2], for example.
ValueNum idxVn = m_pCompiler->vnStore->VNConservativeNormalValue(treeIndex->gtVNPair);
ValueNum arrLenVn = m_pCompiler->vnStore->VNConservativeNormalValue(bndsChk->gtArrLen->gtVNPair);
int arrSize = 0;
if (m_pCompiler->vnStore->IsVNConstant(arrLenVn))
{
ssize_t constVal = -1;
unsigned iconFlags = 0;
if (m_pCompiler->optIsTreeKnownIntValue(true, bndsChk->gtArrLen, &constVal, &iconFlags))
{
arrSize = (int)constVal;
}
}
else
#ifdef FEATURE_SIMD
if (tree->gtOper != GT_SIMD_CHK
#ifdef FEATURE_HW_INTRINSICS
&& tree->gtOper != GT_HW_INTRINSIC_CHK
#endif // FEATURE_HW_INTRINSICS
)
#endif // FEATURE_SIMD
{
arrSize = GetArrLength(arrLenVn);
}
JITDUMP("ArrSize for lengthVN:%03X = %d\n", arrLenVn, arrSize);
if (m_pCompiler->vnStore->IsVNConstant(idxVn) && (arrSize > 0))
{
ssize_t idxVal = -1;
unsigned iconFlags = 0;
if (!m_pCompiler->optIsTreeKnownIntValue(true, treeIndex, &idxVal, &iconFlags))
{
return;
}
JITDUMP("[RangeCheck::OptimizeRangeCheck] Is index %d in <0, arrLenVn " FMT_VN " sz:%d>.\n", idxVal, arrLenVn,
arrSize);
if ((idxVal < arrSize) && (idxVal >= 0))
{
JITDUMP("Removing range check\n");
m_pCompiler->optRemoveRangeCheck(treeParent, stmt);
return;
}
}
GetRangeMap()->RemoveAll();
GetOverflowMap()->RemoveAll();
m_pSearchPath = new (m_alloc) SearchPath(m_alloc);
// Get the range for this index.
Range range = GetRange(block, treeIndex, false DEBUGARG(0));
// If upper or lower limit is found to be unknown (top), or it was found to
// be unknown because of over budget or a deep search, then return early.
if (range.UpperLimit().IsUnknown() || range.LowerLimit().IsUnknown())
{
// Note: If we had stack depth too deep in the GetRange call, we'd be
// too deep even in the DoesOverflow call. So return early.
return;
}
if (DoesOverflow(block, treeIndex))
{
JITDUMP("Method determined to overflow.\n");
return;
}
JITDUMP("Range value %s\n", range.ToString(m_pCompiler->getAllocatorDebugOnly()));
m_pSearchPath->RemoveAll();
Widen(block, treeIndex, &range);
// If upper or lower limit is unknown, then return.
if (range.UpperLimit().IsUnknown() || range.LowerLimit().IsUnknown())
{
return;
}
// Is the range between the lower and upper bound values.
if (BetweenBounds(range, 0, bndsChk->gtArrLen))
{
JITDUMP("[RangeCheck::OptimizeRangeCheck] Between bounds\n");
m_pCompiler->optRemoveRangeCheck(treeParent, stmt);
}
return;
}