bool RangeCheck::IsBinOpMonotonicallyIncreasing(GenTreePtr op1, GenTreePtr op2, genTreeOps oper, SearchPath* path)
{
JITDUMP("[RangeCheck::IsBinOpMonotonicallyIncreasing] %p, %p\n", dspPtr(op1), dspPtr(op2));
// Check if we have a var + const.
if (op2->OperGet() == GT_LCL_VAR)
{
jitstd::swap(op1, op2);
}
if (op1->OperGet() != GT_LCL_VAR)
{
JITDUMP("Not monotonic because op1 is not lclVar.\n");
return false;
}
switch (op2->OperGet())
{
case GT_LCL_VAR:
return IsMonotonicallyIncreasing(op1, path) &&
IsMonotonicallyIncreasing(op2, path);
case GT_CNS_INT:
return oper == GT_ADD && op2->AsIntConCommon()->IconValue() >= 0 &&
IsMonotonicallyIncreasing(op1, path);
default:
JITDUMP("Not monotonic because expression is not recognized.\n");
return false;
}
}
bool RangeCheck::IsBinOpMonotonicallyIncreasing(GenTreeOp* binop)
{
assert(binop->OperIs(GT_ADD));
GenTree* op1 = binop->gtGetOp1();
GenTree* op2 = binop->gtGetOp2();
JITDUMP("[RangeCheck::IsBinOpMonotonicallyIncreasing] [%06d], [%06d]\n", Compiler::dspTreeID(op1),
Compiler::dspTreeID(op2));
// Check if we have a var + const.
if (op2->OperGet() == GT_LCL_VAR)
{
jitstd::swap(op1, op2);
}
if (op1->OperGet() != GT_LCL_VAR)
{
JITDUMP("Not monotonic because op1 is not lclVar.\n");
return false;
}
switch (op2->OperGet())
{
case GT_LCL_VAR:
// When adding two local variables, we also must ensure that any constant is non-negative.
return IsMonotonicallyIncreasing(op1, true) && IsMonotonicallyIncreasing(op2, true);
case GT_CNS_INT:
return (op2->AsIntConCommon()->IconValue() >= 0) && IsMonotonicallyIncreasing(op1, false);
default:
JITDUMP("Not monotonic because expression is not recognized.\n");
return false;
}
}
void RangeCheck::Widen(BasicBlock* block, GenTreePtr stmt, GenTreePtr tree, SearchPath* path, Range* pRange)
{
#ifdef DEBUG
if (m_pCompiler->verbose)
{
printf("[RangeCheck::Widen] BB%02d, \n", block->bbNum);
Compiler::printTreeID(tree);
printf("\n");
}
#endif // DEBUG
Range& range = *pRange;
// Try to deduce the lower bound, if it is not known already.
if (range.LowerLimit().IsDependent() || range.LowerLimit().IsUnknown())
{
// To determine the lower bound, ask if the loop increases monotonically.
bool increasing = IsMonotonicallyIncreasing(tree, path);
JITDUMP("IsMonotonicallyIncreasing %d", increasing);
if (increasing)
{
GetRangeMap()->RemoveAll();
*pRange = GetRange(block, stmt, tree, path, true DEBUGARG(0));
}
}
}
bool RangeCheck::IsMonotonicallyIncreasing(GenTreePtr expr, SearchPath* path)
{
JITDUMP("[RangeCheck::IsMonotonicallyIncreasing] %p\n", dspPtr(expr));
if (path->Lookup(expr))
{
return true;
}
// Add hashtable entry for expr.
path->Set(expr, NULL);
// Remove hashtable entry for expr when we exit the present scope.
auto code = [&] { path->Remove(expr); };
jitstd::utility::scoped_code<decltype(code)> finally(code);
// If the rhs expr is constant, then it is not part of the dependency
// loop which has to increase monotonically.
ValueNum vn = expr->gtVNPair.GetConservative();
if (m_pCompiler->vnStore->IsVNConstant(vn))
{
return true;
}
// If the rhs expr is local, then try to find the def of the local.
else if (expr->IsLocal())
{
Location* loc = GetDef(expr);
if (loc == nullptr)
{
return false;
}
GenTreePtr asg = loc->parent;
assert(asg->OperKind() & GTK_ASGOP);
switch (asg->OperGet())
{
case GT_ASG:
return IsMonotonicallyIncreasing(asg->gtGetOp2(), path);
case GT_ASG_ADD:
return IsBinOpMonotonicallyIncreasing(asg->gtGetOp1(), asg->gtGetOp2(), GT_ADD, path);
}
JITDUMP("Unknown local definition type\n");
return false;
}
else if (expr->OperGet() == GT_ADD)
{
return IsBinOpMonotonicallyIncreasing(expr->gtGetOp1(), expr->gtGetOp2(), GT_ADD, path);
}
else if (expr->OperGet() == GT_PHI)
{
for (GenTreeArgList* args = expr->gtOp.gtOp1->AsArgList();
args != nullptr; args = args->Rest())
{
// If the arg is already in the path, skip.
if (path->Lookup(args->Current()))
{
continue;
}
if (!IsMonotonicallyIncreasing(args->Current(), path))
{
JITDUMP("Phi argument not monotonic\n");
return false;
}
}
return true;
}
JITDUMP("Unknown tree type\n");
return false;
}
// The parameter rejectNegativeConst is true when we are adding two local vars (see above)
bool RangeCheck::IsMonotonicallyIncreasing(GenTree* expr, bool rejectNegativeConst)
{
JITDUMP("[RangeCheck::IsMonotonicallyIncreasing] [%06d]\n", Compiler::dspTreeID(expr));
// Add hashtable entry for expr.
bool alreadyPresent = !m_pSearchPath->Set(expr, nullptr, SearchPath::Overwrite);
if (alreadyPresent)
{
return true;
}
// Remove hashtable entry for expr when we exit the present scope.
auto code = [this, expr] { m_pSearchPath->Remove(expr); };
jitstd::utility::scoped_code<decltype(code)> finally(code);
if (m_pSearchPath->GetCount() > MAX_SEARCH_DEPTH)
{
return false;
}
// If expr is constant, then it is not part of the dependency
// loop which has to increase monotonically.
ValueNum vn = expr->gtVNPair.GetConservative();
if (m_pCompiler->vnStore->IsVNInt32Constant(vn))
{
if (rejectNegativeConst)
{
int cons = m_pCompiler->vnStore->ConstantValue<int>(vn);
return (cons >= 0);
}
else
{
return true;
}
}
// If the rhs expr is local, then try to find the def of the local.
else if (expr->IsLocal())
{
BasicBlock* asgBlock;
GenTreeOp* asg = GetSsaDefAsg(expr->AsLclVarCommon(), &asgBlock);
return (asg != nullptr) && IsMonotonicallyIncreasing(asg->gtGetOp2(), rejectNegativeConst);
}
else if (expr->OperGet() == GT_ADD)
{
return IsBinOpMonotonicallyIncreasing(expr->AsOp());
}
else if (expr->OperGet() == GT_PHI)
{
for (GenTreeArgList* args = expr->gtOp.gtOp1->AsArgList(); args != nullptr; args = args->Rest())
{
// If the arg is already in the path, skip.
if (m_pSearchPath->Lookup(args->Current()))
{
continue;
}
if (!IsMonotonicallyIncreasing(args->Current(), rejectNegativeConst))
{
JITDUMP("Phi argument not monotonic\n");
return false;
}
}
return true;
}
JITDUMP("Unknown tree type\n");
return false;
}
