Skip to content

Commit

Permalink
JIT: revise local assertion prop to use bit vectors for live assertio…
Browse files Browse the repository at this point in the history 
…n tracking (#94322)

Track the set of active local assertions via a bit vector, rather than assuming
all entries in the table are live.

Doing so required a number of changes in assertion prop to ensure the vector
is consulted before deciding an assertion is valid.

This will (eventually) allow us to propagate assertions cross-block. For
now we reset the bit vector and assertion table back to empty at the start
of each block so nothing propagates past the end of a block.

The table can fill and cause the JIT to miss assertions in very large blocks
as morph will no longer remove assertions while processing a block. Previously
this would happen if there were more than 64 live assertions in a block, and
now it can happen if there are more than 64 assertions in block (so somewhat
more frequently).

Contributes to #93246.
  • Loading branch information
@AndyAyersMS
AndyAyersMS authored Nov 3, 2023
1 parent ede2cb2 commit 3f70252
Show file tree
Hide file tree
Showing 5 changed files with 124 additions and 143 deletions.
41 changes: 25 additions & 16 deletions src/coreclr/jit/assertionprop.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -554,14 +554,14 @@ void Compiler::optAssertionInit(bool isLocalProp)

optLocalAssertionProp = isLocalProp;
optAssertionTabPrivate = new (this, CMK_AssertionProp) AssertionDsc[optMaxAssertionCount];
optComplementaryAssertionMap =
new (this, CMK_AssertionProp) AssertionIndex[optMaxAssertionCount + 1](); // zero-inited (NO_ASSERTION_INDEX)
assert(NO_ASSERTION_INDEX == 0);

if (!isLocalProp)
{
optValueNumToAsserts =
new (getAllocator(CMK_AssertionProp)) ValueNumToAssertsMap(getAllocator(CMK_AssertionProp));
optComplementaryAssertionMap = new (this, CMK_AssertionProp)
AssertionIndex[optMaxAssertionCount + 1](); // zero-inited (NO_ASSERTION_INDEX)
}

if (optAssertionDep == nullptr)
Expand All @@ -572,6 +572,7 @@ void Compiler::optAssertionInit(bool isLocalProp)

optAssertionTraitsInit(optMaxAssertionCount);
optAssertionCount = 0;
optAssertionOverflow = 0;
optAssertionPropagated = false;
bbJtrueAssertionOut = nullptr;
optCanPropLclVar = false;
Expand Down Expand Up @@ -1607,6 +1608,7 @@ AssertionIndex Compiler::optAddAssertion(AssertionDsc* newAssertion)
// Check if we are within max count.
if (optAssertionCount >= optMaxAssertionCount)
{
optAssertionOverflow++;
return NO_ASSERTION_INDEX;
}

Expand Down Expand Up @@ -2370,8 +2372,7 @@ void Compiler::optAssertionGen(GenTree* tree)
break;
}

// For global assertion prop we must store the assertion number in the tree node
if (assertionInfo.HasAssertion() && assertionProven && !optLocalAssertionProp)
if (assertionInfo.HasAssertion() && assertionProven)
{
tree->SetAssertionInfo(assertionInfo);
}
Expand Down Expand Up @@ -2459,9 +2460,7 @@ AssertionIndex Compiler::optAssertionIsSubrange(GenTree* tree, IntegralRange ran
for (AssertionIndex index = 1; index <= optAssertionCount; index++)
{
AssertionDsc* curAssertion = optGetAssertion(index);
if ((optLocalAssertionProp ||
BitVecOps::IsMember(apTraits, assertions, index - 1)) && // either local prop or use propagated assertions
curAssertion->CanPropSubRange())
if (BitVecOps::IsMember(apTraits, assertions, index - 1) && curAssertion->CanPropSubRange())
{
// For local assertion prop use comparison on locals, and use comparison on vns for global prop.
bool isEqual = optLocalAssertionProp
Expand Down Expand Up @@ -2493,13 +2492,13 @@ AssertionIndex Compiler::optAssertionIsSubrange(GenTree* tree, IntegralRange ran
*/
AssertionIndex Compiler::optAssertionIsSubtype(GenTree* tree, GenTree* methodTableArg, ASSERT_VALARG_TP assertions)
{
if (!optLocalAssertionProp && BitVecOps::IsEmpty(apTraits, assertions))
if (BitVecOps::IsEmpty(apTraits, assertions))
{
return NO_ASSERTION_INDEX;
}
for (AssertionIndex index = 1; index <= optAssertionCount; index++)
{
if (!optLocalAssertionProp && !BitVecOps::IsMember(apTraits, assertions, index - 1))
if (!BitVecOps::IsMember(apTraits, assertions, index - 1))
{
continue;
}
Expand Down Expand Up @@ -3594,15 +3593,15 @@ AssertionIndex Compiler::optLocalAssertionIsEqualOrNotEqual(
{
noway_assert((op1Kind == O1K_LCLVAR) || (op1Kind == O1K_EXACT_TYPE) || (op1Kind == O1K_SUBTYPE));
noway_assert((op2Kind == O2K_CONST_INT) || (op2Kind == O2K_IND_CNS_INT) || (op2Kind == O2K_ZEROOBJ));
if (!optLocalAssertionProp && BitVecOps::IsEmpty(apTraits, assertions))
if (BitVecOps::IsEmpty(apTraits, assertions))
{
return NO_ASSERTION_INDEX;
}

for (AssertionIndex index = 1; index <= optAssertionCount; ++index)
{
AssertionDsc* curAssertion = optGetAssertion(index);
if (optLocalAssertionProp || BitVecOps::IsMember(apTraits, assertions, index - 1))
if (BitVecOps::IsMember(apTraits, assertions, index - 1))
{
if ((curAssertion->assertionKind != OAK_EQUAL) && (curAssertion->assertionKind != OAK_NOT_EQUAL))
{
Expand Down Expand Up @@ -4386,17 +4385,27 @@ AssertionIndex Compiler::optAssertionIsNonNullInternal(GenTree* op,
}
else
{
unsigned lclNum = op->AsLclVarCommon()->GetLclNum();
// Check each assertion to find if we have a variable == or != null assertion.
for (AssertionIndex index = 1; index <= optAssertionCount; index++)
// Find live assertions related to lclNum
//
unsigned const lclNum = op->AsLclVarCommon()->GetLclNum();
ASSERT_TP apDependent = GetAssertionDep(lclNum);
BitVecOps::IntersectionD(apTraits, apDependent, apLocal);

// Scan those looking for a suitable assertion
//
BitVecOps::Iter iter(apTraits, assertions);
unsigned index = 0;
while (iter.NextElem(&index))
{
AssertionDsc* curAssertion = optGetAssertion(index);
AssertionIndex assertionIndex = GetAssertionIndex(index);
AssertionDsc* curAssertion = optGetAssertion(assertionIndex);

if ((curAssertion->assertionKind == OAK_NOT_EQUAL) && // kind
(curAssertion->op1.kind == O1K_LCLVAR) && // op1
(curAssertion->op2.kind == O2K_CONST_INT) && // op2
(curAssertion->op1.lcl.lclNum == lclNum) && (curAssertion->op2.u1.iconVal == 0))
{
return index;
return assertionIndex;
}
}
}
Expand Down
4 changes: 2 additions & 2 deletions src/coreclr/jit/bitset.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -172,11 +172,11 @@ class BitSetOps
// Returns "true" iff "bs" may be the uninit value.
static bool MayBeUninit(BitSetValueArgType bs);

// Returns the a new BitSet that is empty. Uses the Allocator of "env" to allocate memory for
// Returns a new BitSet that is empty. Uses the Allocator of "env" to allocate memory for
// the representation, if necessary.
static BitSetValueRetType MakeEmpty(Env env);

// Returns the a new BitSet that is "full" -- represents all the integers in the current range.
// Returns a new BitSet that is "full" -- represents all the integers in the current range.
// Uses the Allocator of "env" to allocate memory for the representation, if necessary.
static BitSetValueRetType MakeFull(Env env);

Expand Down
3 changes: 3 additions & 0 deletions src/coreclr/jit/compiler.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6064,6 +6064,7 @@ class Compiler
GenTree* fgMorphTree(GenTree* tree, MorphAddrContext* mac = nullptr);

private:
void fgAssertionGen(GenTree* tree);
void fgKillDependentAssertionsSingle(unsigned lclNum DEBUGARG(GenTree* tree));
void fgKillDependentAssertions(unsigned lclNum DEBUGARG(GenTree* tree));
void fgMorphTreeDone(GenTree* tree);
Expand Down Expand Up @@ -7354,6 +7355,7 @@ class Compiler
// Data structures for assertion prop
BitVecTraits* apTraits;
ASSERT_TP apFull;
ASSERT_TP apLocal;

enum optAssertionKind
{
Expand Down Expand Up @@ -7638,6 +7640,7 @@ class Compiler
AssertionDsc* optAssertionTabPrivate; // table that holds info about value assignments
AssertionIndex optAssertionCount; // total number of assertions in the assertion table
AssertionIndex optMaxAssertionCount;
unsigned optAssertionOverflow;
bool optCanPropLclVar;
bool optCanPropEqual;
bool optCanPropNonNull;
Expand Down
Loading

0 comments on commit 3f70252

Please sign in to comment.