// Merge assertions on the edge flowing into the block about a variable.
void RangeCheck::MergeEdgeAssertions(GenTreePtr tree, EXPSET_TP assertions, Range* pRange)
{
if (assertions == 0)
{
return;
}
GenTreeLclVarCommon* lcl = (GenTreeLclVarCommon*) tree;
if (lcl->gtSsaNum == SsaConfig::RESERVED_SSA_NUM)
{
return;
}
// Walk through the "assertions" to check if the apply.
unsigned index = 1;
for (EXPSET_TP mask = 1; index <= m_pCompiler->GetAssertionCount(); index++, mask <<= 1)
{
if ((assertions & mask) == 0)
{
continue;
}
Compiler::AssertionDsc* curAssertion = m_pCompiler->optGetAssertion(index);
// Current assertion is about array length.
if (!curAssertion->IsArrLenArithBound() &&
!curAssertion->IsArrLenBound())
{
continue;
}
#ifdef DEBUG
if (m_pCompiler->verbose)
{
m_pCompiler->optPrintAssertion(curAssertion, index);
}
#endif
assert(m_pCompiler->vnStore->IsVNArrLenArithBound(curAssertion->op1.vn) ||
m_pCompiler->vnStore->IsVNArrLenBound(curAssertion->op1.vn));
ValueNumStore::ArrLenArithBoundInfo info;
Limit limit(Limit::keUndef);
// Current assertion is of the form (i < a.len - cns) != 0
if (curAssertion->IsArrLenArithBound())
{
// Get i, a.len, cns and < as "info."
m_pCompiler->vnStore->GetArrLenArithBoundInfo(curAssertion->op1.vn, &info);
if (m_pCompiler->lvaTable[lcl->gtLclNum].GetPerSsaData(lcl->gtSsaNum)->m_vnPair.GetConservative()
!= info.cmpOp)
{
continue;
}
switch (info.arrOper)
{
case GT_SUB:
case GT_ADD:
{
// If the operand that operates on the array is not constant, then done.
if (!m_pCompiler->vnStore->IsVNConstant(info.arrOp) || m_pCompiler->vnStore->TypeOfVN(info.arrOp) != TYP_INT)
{
break;
}
int cons = m_pCompiler->vnStore->ConstantValue<int>(info.arrOp);
limit = Limit(Limit::keBinOpArray, info.vnArray, info.arrOper == GT_SUB ? -cons : cons);
}
}
}
// Current assertion is of the form (i < a.len) != 0
else if (curAssertion->IsArrLenBound())
{
// Get the info as "i", "<" and "a.len"
m_pCompiler->vnStore->GetArrLenBoundInfo(curAssertion->op1.vn, &info);
ValueNum lclVn = m_pCompiler->lvaTable[lcl->gtLclNum].GetPerSsaData(lcl->gtSsaNum)->m_vnPair.GetConservative();
// If we don't have the same variable we are comparing against, bail.
if (lclVn != info.cmpOp)
{
continue;
}
limit.type = Limit::keArray;
limit.vn = info.vnArray;
}
else
{
noway_assert(false);
}
if (limit.IsUndef())
{
continue;
}
// Make sure the assertion is of the form != 0 or == 0.
if (curAssertion->op2.vn != m_pCompiler->vnStore->VNZeroForType(TYP_INT))
{
continue;
}
#ifdef DEBUG
if (m_pCompiler->verbose) m_pCompiler->optPrintAssertion(curAssertion, index);
#endif
noway_assert(limit.IsBinOpArray() || limit.IsArray());
ValueNum arrLenVN = m_pCurBndsChk->gtArrLen->gtVNPair.GetConservative();
ValueNum arrRefVN = m_pCompiler->vnStore->GetArrForLenVn(arrLenVN);
// During assertion prop we add assertions of the form:
//
// (i < a.Length) == 0
// (i < a.Length) != 0
//
// At this point, we have detected that op1.vn is (i < a.Length) or (i < a.Length + cns),
// and the op2.vn is 0.
//
// Now, let us check if we are == 0 (i.e., op1 assertion is false) or != 0 (op1 assertion
// is true.),
//
// If we have an assertion of the form == 0 (i.e., equals false), then reverse relop.
// The relop has to be reversed because we have: (i < a.Length) is false which is the same
// as (i >= a.Length).
genTreeOps cmpOper = (genTreeOps) info.cmpOper;
if (curAssertion->assertionKind == Compiler::OAK_EQUAL)
{
cmpOper = GenTree::ReverseRelop(cmpOper);
}
// Bounds are inclusive, so add -1 for upper bound when "<". But make sure we won't overflow.
if (cmpOper == GT_LT && !limit.AddConstant(-1))
{
continue;
}
// Bounds are inclusive, so add +1 for lower bound when ">". But make sure we won't overflow.
if (cmpOper == GT_GT && !limit.AddConstant(1))
{
continue;
}
// Doesn't tighten the current bound. So skip.
if (pRange->uLimit.IsConstant() && limit.vn != arrRefVN)
{
continue;
}
// Check if the incoming limit from assertions tightens the existing upper limit.
if ((pRange->uLimit.IsArray() || pRange->uLimit.IsBinOpArray()) && pRange->uLimit.vn == arrRefVN)
{
// We have checked the current range's (pRange's) upper limit is either of the form:
// a.Length
// a.Length + cns
// and a == the bndsChkCandidate's arrRef
//
// We want to check if the incoming limit tightens the bound, and for that the
// we need to make sure that incoming limit is also on a.Length or a.Length + cns
// and not b.Length or some c.Length.
if (limit.vn != arrRefVN)
{
JITDUMP("Array ref did not match cur=$%x, assert=$%x\n", arrRefVN, limit.vn);
continue;
}
int curCns = (pRange->uLimit.IsBinOpArray()) ? pRange->uLimit.cns : 0;
int limCns = (limit.IsBinOpArray()) ? limit.cns : 0;
// Incoming limit doesn't tighten the existing upper limit.
if (limCns >= curCns)
{
JITDUMP("Bound limit %d doesn't tighten current bound %d\n", limCns, curCns);
continue;
}
}
else
{
// Current range's upper bound is not "a.Length or a.Length + cns" and the
// incoming limit is not on the same arrRef as the bounds check candidate.
// So we could skip this assertion. But in cases, of Dependent or Unknown
// type of upper limit, the incoming assertion still tightens the upper
// bound to a saner value. So do not skip the assertion.
}
// cmpOp (loop index i) cmpOper a.len +/- cns
switch (cmpOper)
{
case GT_LT:
pRange->uLimit = limit;
break;
case GT_GT:
pRange->lLimit = limit;
break;
case GT_GE:
pRange->lLimit = limit;
break;
case GT_LE:
pRange->uLimit = limit;
break;
}
JITDUMP("The range after edge merging:");
JITDUMP(pRange->ToString(m_pCompiler->getAllocatorDebugOnly()));
JITDUMP("\n");
}
}
// Merge assertions on the edge flowing into the block about a variable.
void RangeCheck::MergeEdgeAssertions(GenTreeLclVarCommon* lcl, ASSERT_VALARG_TP assertions, Range* pRange)
{
if (BitVecOps::IsEmpty(m_pCompiler->apTraits, assertions))
{
return;
}
if (lcl->gtSsaNum == SsaConfig::RESERVED_SSA_NUM)
{
return;
}
// Walk through the "assertions" to check if the apply.
BitVecOps::Iter iter(m_pCompiler->apTraits, assertions);
unsigned index = 0;
while (iter.NextElem(&index))
{
AssertionIndex assertionIndex = GetAssertionIndex(index);
Compiler::AssertionDsc* curAssertion = m_pCompiler->optGetAssertion(assertionIndex);
Limit limit(Limit::keUndef);
genTreeOps cmpOper = GT_NONE;
LclSsaVarDsc* ssaData = m_pCompiler->lvaTable[lcl->gtLclNum].GetPerSsaData(lcl->gtSsaNum);
ValueNum normalLclVN = m_pCompiler->vnStore->VNConservativeNormalValue(ssaData->m_vnPair);
// Current assertion is of the form (i < len - cns) != 0
if (curAssertion->IsCheckedBoundArithBound())
{
ValueNumStore::CompareCheckedBoundArithInfo info;
// Get i, len, cns and < as "info."
m_pCompiler->vnStore->GetCompareCheckedBoundArithInfo(curAssertion->op1.vn, &info);
// If we don't have the same variable we are comparing against, bail.
if (normalLclVN != info.cmpOp)
{
continue;
}
if ((info.arrOper != GT_ADD) && (info.arrOper != GT_SUB))
{
continue;
}
// If the operand that operates on the bound is not constant, then done.
if (!m_pCompiler->vnStore->IsVNInt32Constant(info.arrOp))
{
continue;
}
int cons = m_pCompiler->vnStore->ConstantValue<int>(info.arrOp);
limit = Limit(Limit::keBinOpArray, info.vnBound, info.arrOper == GT_SUB ? -cons : cons);
cmpOper = (genTreeOps)info.cmpOper;
}
// Current assertion is of the form (i < len) != 0
else if (curAssertion->IsCheckedBoundBound())
{
ValueNumStore::CompareCheckedBoundArithInfo info;
// Get the info as "i", "<" and "len"
m_pCompiler->vnStore->GetCompareCheckedBound(curAssertion->op1.vn, &info);
// If we don't have the same variable we are comparing against, bail.
if (normalLclVN != info.cmpOp)
{
continue;
}
limit = Limit(Limit::keBinOpArray, info.vnBound, 0);
cmpOper = (genTreeOps)info.cmpOper;
}
// Current assertion is of the form (i < 100) != 0
else if (curAssertion->IsConstantBound())
{
ValueNumStore::ConstantBoundInfo info;
// Get the info as "i", "<" and "100"
m_pCompiler->vnStore->GetConstantBoundInfo(curAssertion->op1.vn, &info);
// If we don't have the same variable we are comparing against, bail.
if (normalLclVN != info.cmpOpVN)
{
continue;
}
limit = Limit(Limit::keConstant, info.constVal);
cmpOper = (genTreeOps)info.cmpOper;
}
// Current assertion is not supported, ignore it
else
{
continue;
}
assert(limit.IsBinOpArray() || limit.IsConstant());
// Make sure the assertion is of the form != 0 or == 0.
if (curAssertion->op2.vn != m_pCompiler->vnStore->VNZeroForType(TYP_INT))
{
continue;
}
#ifdef DEBUG
if (m_pCompiler->verbose)
{
m_pCompiler->optPrintAssertion(curAssertion, assertionIndex);
}
#endif
ValueNum arrLenVN = m_pCompiler->vnStore->VNConservativeNormalValue(m_pCurBndsChk->gtArrLen->gtVNPair);
if (m_pCompiler->vnStore->IsVNConstant(arrLenVN))
{
// Set arrLenVN to NoVN; this will make it match the "vn" recorded on
// constant limits (where we explicitly track the constant and don't
// redundantly store its VN in the "vn" field).
arrLenVN = ValueNumStore::NoVN;
}
// During assertion prop we add assertions of the form:
//
// (i < length) == 0
// (i < length) != 0
// (i < 100) == 0
// (i < 100) != 0
//
// At this point, we have detected that op1.vn is (i < length) or (i < length + cns) or
// (i < 100) and the op2.vn is 0.
//
// Now, let us check if we are == 0 (i.e., op1 assertion is false) or != 0 (op1 assertion
// is true.),
//
// If we have an assertion of the form == 0 (i.e., equals false), then reverse relop.
// The relop has to be reversed because we have: (i < length) is false which is the same
// as (i >= length).
if (curAssertion->assertionKind == Compiler::OAK_EQUAL)
{
cmpOper = GenTree::ReverseRelop(cmpOper);
}
// Bounds are inclusive, so add -1 for upper bound when "<". But make sure we won't overflow.
if (cmpOper == GT_LT && !limit.AddConstant(-1))
{
continue;
}
// Bounds are inclusive, so add +1 for lower bound when ">". But make sure we won't overflow.
if (cmpOper == GT_GT && !limit.AddConstant(1))
{
continue;
}
// Doesn't tighten the current bound. So skip.
if (pRange->uLimit.IsConstant() && limit.vn != arrLenVN)
{
continue;
}
// Check if the incoming limit from assertions tightens the existing upper limit.
if (pRange->uLimit.IsBinOpArray() && (pRange->uLimit.vn == arrLenVN))
{
// We have checked the current range's (pRange's) upper limit is either of the form:
// length + cns
// and length == the bndsChkCandidate's arrLen
//
// We want to check if the incoming limit tightens the bound, and for that
// we need to make sure that incoming limit is also on the same length (or
// length + cns) and not some other length.
if (limit.vn != arrLenVN)
{
JITDUMP("Array length VN did not match arrLen=" FMT_VN ", limit=" FMT_VN "\n", arrLenVN, limit.vn);
continue;
}
int curCns = pRange->uLimit.cns;
int limCns = (limit.IsBinOpArray()) ? limit.cns : 0;
// Incoming limit doesn't tighten the existing upper limit.
if (limCns >= curCns)
{
JITDUMP("Bound limit %d doesn't tighten current bound %d\n", limCns, curCns);
continue;
}
}
else
{
// Current range's upper bound is not "length + cns" and the
// incoming limit is not on the same length as the bounds check candidate.
// So we could skip this assertion. But in cases, of Dependent or Unknown
// type of upper limit, the incoming assertion still tightens the upper
// bound to a saner value. So do not skip the assertion.
}
// cmpOp (loop index i) cmpOper len +/- cns
switch (cmpOper)
{
case GT_LT:
pRange->uLimit = limit;
break;
case GT_GT:
pRange->lLimit = limit;
break;
case GT_GE:
pRange->lLimit = limit;
break;
case GT_LE:
pRange->uLimit = limit;
break;
default:
// All other 'cmpOper' kinds leave lLimit/uLimit unchanged
break;
}
JITDUMP("The range after edge merging:");
JITDUMP(pRange->ToString(m_pCompiler->getAllocatorDebugOnly()));
JITDUMP("\n");
}
}