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Propagate assertions for more checked bounds
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Generalize (and rename) the assertion/limit code for tracking array
lengths (which have until now been recognized by the VNFunc being
GT_ARR_LENGTH) to track all values that appear in the function as
length arguments to bounds chcks nodes.  Add a hashtable to identify that
set of value numbers, `m_checkedBoundVNs` to the VNStore object, and
populate it during value-numbering.  Wherever names were adjusted, the
generalization of "array length" is called "checked bound".

This allows the array bound check removal machinery to operate on span
bound checks as well.
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@JosephTremoulet
JosephTremoulet committed May 11, 2017
1 parent cda51e4 commit 72e126a
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Showing 6 changed files with 292 additions and 231 deletions.
68 changes: 34 additions & 34 deletions src/jit/assertionprop.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -627,12 +627,12 @@ void Compiler::optPrintAssertion(AssertionDsc* curAssertion, AssertionIndex asse
vnStore->vnDump(this, curAssertion->op1.bnd.vnLen);
printf("]");
}
else if (curAssertion->op1.kind == O1K_ARRLEN_OPER_BND)
else if (curAssertion->op1.kind == O1K_BOUND_OPER_BND)
{
printf("Oper_Bnd");
vnStore->vnDump(this, curAssertion->op1.vn);
}
else if (curAssertion->op1.kind == O1K_ARRLEN_LOOP_BND)
else if (curAssertion->op1.kind == O1K_BOUND_LOOP_BND)
{
printf("Loop_Bnd");
vnStore->vnDump(this, curAssertion->op1.vn);
Expand Down Expand Up @@ -711,12 +711,12 @@ void Compiler::optPrintAssertion(AssertionDsc* curAssertion, AssertionIndex asse
printf("MT(%08X)", dspPtr(curAssertion->op2.u1.iconVal));
assert(curAssertion->op2.u1.iconFlags != 0);
}
else if (curAssertion->op1.kind == O1K_ARRLEN_OPER_BND)
else if (curAssertion->op1.kind == O1K_BOUND_OPER_BND)
{
assert(!optLocalAssertionProp);
vnStore->vnDump(this, curAssertion->op2.vn);
}
else if (curAssertion->op1.kind == O1K_ARRLEN_LOOP_BND)
else if (curAssertion->op1.kind == O1K_BOUND_LOOP_BND)
{
assert(!optLocalAssertionProp);
vnStore->vnDump(this, curAssertion->op2.vn);
Expand Down Expand Up @@ -1625,8 +1625,8 @@ void Compiler::optDebugCheckAssertion(AssertionDsc* assertion)
case O1K_ARR_BND:
// It would be good to check that bnd.vnIdx and bnd.vnLen are valid value numbers.
break;
case O1K_ARRLEN_OPER_BND:
case O1K_ARRLEN_LOOP_BND:
case O1K_BOUND_OPER_BND:
case O1K_BOUND_LOOP_BND:
case O1K_CONSTANT_LOOP_BND:
case O1K_VALUE_NUMBER:
assert(!optLocalAssertionProp);
Expand Down Expand Up @@ -1702,7 +1702,7 @@ void Compiler::optCreateComplementaryAssertion(AssertionIndex assertionIndex, Ge
}

AssertionDsc& candidateAssertion = *optGetAssertion(assertionIndex);
if (candidateAssertion.op1.kind == O1K_ARRLEN_OPER_BND || candidateAssertion.op1.kind == O1K_ARRLEN_LOOP_BND ||
if (candidateAssertion.op1.kind == O1K_BOUND_OPER_BND || candidateAssertion.op1.kind == O1K_BOUND_LOOP_BND ||
candidateAssertion.op1.kind == O1K_CONSTANT_LOOP_BND)
{
AssertionDsc dsc = candidateAssertion;
Expand Down Expand Up @@ -1768,17 +1768,17 @@ AssertionInfo Compiler::optCreateJTrueBoundsAssertion(GenTreePtr tree)

ValueNum vn = op1->gtVNPair.GetConservative();

ValueNumStore::ArrLenUnsignedBoundInfo arrLenUnsignedBnd;
// Cases where op1 holds the condition with array arithmetic and op2 is 0.
// Loop condition like: "i < a.len +/-k == 0"
// Assertion: "i < a.len +/- k == 0"
if (vnStore->IsVNArrLenArithBound(vn) &&
ValueNumStore::UnsignedCompareCheckedBoundInfo unsignedCompareBnd;
// Cases where op1 holds the upper bound arithmetic and op2 is 0.
// Loop condition like: "i < bnd +/-k == 0"
// Assertion: "i < bnd +/- k == 0"
if (vnStore->IsVNCompareCheckedBoundArith(vn) &&
op2->gtVNPair.GetConservative() == vnStore->VNZeroForType(op2->TypeGet()) &&
(relop->gtOper == GT_EQ || relop->gtOper == GT_NE))
{
AssertionDsc dsc;
dsc.assertionKind = relop->gtOper == GT_EQ ? OAK_EQUAL : OAK_NOT_EQUAL;
dsc.op1.kind = O1K_ARRLEN_OPER_BND;
dsc.op1.kind = O1K_BOUND_OPER_BND;
dsc.op1.vn = vn;
dsc.op2.kind = O2K_CONST_INT;
dsc.op2.vn = vnStore->VNZeroForType(op2->TypeGet());
Expand All @@ -1788,16 +1788,16 @@ AssertionInfo Compiler::optCreateJTrueBoundsAssertion(GenTreePtr tree)
optCreateComplementaryAssertion(index, nullptr, nullptr);
return index;
}
// Cases where op1 holds the condition array length and op2 is 0.
// Loop condition like: "i < a.len == 0"
// Assertion: "i < a.len == false"
else if (vnStore->IsVNArrLenBound(vn) &&
// Cases where op1 holds the upper bound and op2 is 0.
// Loop condition like: "i < bnd == 0"
// Assertion: "i < bnd == false"
else if (vnStore->IsVNCompareCheckedBound(vn) &&
(op2->gtVNPair.GetConservative() == vnStore->VNZeroForType(op2->TypeGet())) &&
(relop->gtOper == GT_EQ || relop->gtOper == GT_NE))
{
AssertionDsc dsc;
dsc.assertionKind = relop->gtOper == GT_EQ ? OAK_EQUAL : OAK_NOT_EQUAL;
dsc.op1.kind = O1K_ARRLEN_LOOP_BND;
dsc.op1.kind = O1K_BOUND_LOOP_BND;
dsc.op1.vn = vn;
dsc.op2.kind = O2K_CONST_INT;
dsc.op2.vn = vnStore->VNZeroForType(op2->TypeGet());
Expand All @@ -1807,14 +1807,14 @@ AssertionInfo Compiler::optCreateJTrueBoundsAssertion(GenTreePtr tree)
optCreateComplementaryAssertion(index, nullptr, nullptr);
return index;
}
// Cases where op1 holds the lhs of the condition op2 holds rhs.
// Loop condition like "i < a.len"
// Assertion: "i < a.len != 0"
else if (vnStore->IsVNArrLenBound(relop->gtVNPair.GetConservative()))
// Cases where op1 holds the lhs of the condition op2 holds the bound.
// Loop condition like "i < bnd"
// Assertion: "i < bnd != 0"
else if (vnStore->IsVNCompareCheckedBound(relop->gtVNPair.GetConservative()))
{
AssertionDsc dsc;
dsc.assertionKind = OAK_NOT_EQUAL;
dsc.op1.kind = O1K_ARRLEN_LOOP_BND;
dsc.op1.kind = O1K_BOUND_LOOP_BND;
dsc.op1.vn = relop->gtVNPair.GetConservative();
dsc.op2.kind = O2K_CONST_INT;
dsc.op2.vn = vnStore->VNZeroForType(TYP_INT);
Expand All @@ -1824,28 +1824,28 @@ AssertionInfo Compiler::optCreateJTrueBoundsAssertion(GenTreePtr tree)
optCreateComplementaryAssertion(index, nullptr, nullptr);
return index;
}
// Loop condition like "(uint)i < (uint)a.len" or equivalent
// Assertion: "no throw" since this condition guarantees that i is both >= 0 and < a.len (on the appropiate edge)
else if (vnStore->IsVNArrLenUnsignedBound(relop->gtVNPair.GetConservative(), &arrLenUnsignedBnd))
// Loop condition like "(uint)i < (uint)bnd" or equivalent
// Assertion: "no throw" since this condition guarantees that i is both >= 0 and < bnd (on the appropiate edge)
else if (vnStore->IsVNUnsignedCompareCheckedBound(relop->gtVNPair.GetConservative(), &unsignedCompareBnd))
{
assert(arrLenUnsignedBnd.vnIdx != ValueNumStore::NoVN);
assert((arrLenUnsignedBnd.cmpOper == VNF_LT_UN) || (arrLenUnsignedBnd.cmpOper == VNF_GE_UN));
assert(vnStore->IsVNArrLen(arrLenUnsignedBnd.vnLen));
assert(unsignedCompareBnd.vnIdx != ValueNumStore::NoVN);
assert((unsignedCompareBnd.cmpOper == VNF_LT_UN) || (unsignedCompareBnd.cmpOper == VNF_GE_UN));
assert(vnStore->IsVNCheckedBound(unsignedCompareBnd.vnBound));

AssertionDsc dsc;
dsc.assertionKind = OAK_NO_THROW;
dsc.op1.kind = O1K_ARR_BND;
dsc.op1.vn = relop->gtVNPair.GetConservative();
dsc.op1.bnd.vnIdx = arrLenUnsignedBnd.vnIdx;
dsc.op1.bnd.vnLen = arrLenUnsignedBnd.vnLen;
dsc.op1.bnd.vnIdx = unsignedCompareBnd.vnIdx;
dsc.op1.bnd.vnLen = unsignedCompareBnd.vnBound;
dsc.op2.kind = O2K_INVALID;
dsc.op2.vn = ValueNumStore::NoVN;

AssertionIndex index = optAddAssertion(&dsc);
if (arrLenUnsignedBnd.cmpOper == VNF_GE_UN)
if (unsignedCompareBnd.cmpOper == VNF_GE_UN)
{
// By default JTRUE generated assertions hold on the "jump" edge. We have i >= a.len but we're really
// after i < a.len so we need to change the assertion edge to "next".
// By default JTRUE generated assertions hold on the "jump" edge. We have i >= bnd but we're really
// after i < bnd so we need to change the assertion edge to "next".
return AssertionInfo::ForNextEdge(index);
}
return index;
Expand Down
20 changes: 10 additions & 10 deletions src/jit/compiler.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5493,11 +5493,11 @@ class Compiler

typedef SimplerHashTable<GenTreePtr, PtrKeyFuncs<GenTree>, GenTreePtr, JitSimplerHashBehavior> NodeToNodeMap;

NodeToNodeMap* optCseArrLenMap; // Maps array length nodes to ancestor compares that should be
// re-numbered with the array length to improve range check elimination
NodeToNodeMap* optCseCheckedBoundMap; // Maps bound nodes to ancestor compares that should be
// re-numbered with the bound to improve range check elimination

// Given a compare, look for a cse candidate arrlen feeding it and add a map entry if found.
void optCseUpdateArrLenMap(GenTreePtr compare);
// Given a compare, look for a cse candidate checked bound feeding it and add a map entry if found.
void optCseUpdateCheckedBoundMap(GenTreePtr compare);

void optCSEstop();

Expand Down Expand Up @@ -5726,8 +5726,8 @@ class Compiler
O1K_INVALID,
O1K_LCLVAR,
O1K_ARR_BND,
O1K_ARRLEN_OPER_BND,
O1K_ARRLEN_LOOP_BND,
O1K_BOUND_OPER_BND,
O1K_BOUND_LOOP_BND,
O1K_CONSTANT_LOOP_BND,
O1K_EXACT_TYPE,
O1K_SUBTYPE,
Expand Down Expand Up @@ -5792,13 +5792,13 @@ class Compiler
};
} op2;

bool IsArrLenArithBound()
bool IsCheckedBoundArithBound()
{
return ((assertionKind == OAK_EQUAL || assertionKind == OAK_NOT_EQUAL) && op1.kind == O1K_ARRLEN_OPER_BND);
return ((assertionKind == OAK_EQUAL || assertionKind == OAK_NOT_EQUAL) && op1.kind == O1K_BOUND_OPER_BND);
}
bool IsArrLenBound()
bool IsCheckedBoundBound()
{
return ((assertionKind == OAK_EQUAL || assertionKind == OAK_NOT_EQUAL) && op1.kind == O1K_ARRLEN_LOOP_BND);
return ((assertionKind == OAK_EQUAL || assertionKind == OAK_NOT_EQUAL) && op1.kind == O1K_BOUND_LOOP_BND);
}
bool IsConstantBound()
{
Expand Down
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