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Late cast expansion: more improvements #2 (dotnet#97480)
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@EgorBo
EgorBo authored Jan 29, 2024
1 parent 9bbfa9a commit 34bf05f
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Showing 2 changed files with 59 additions and 50 deletions.
100 changes: 57 additions & 43 deletions src/coreclr/jit/helperexpansion.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1828,31 +1828,12 @@ bool Compiler::fgVNBasedIntrinsicExpansionForCall_ReadUtf8(BasicBlock** pBlock,
//
PhaseStatus Compiler::fgLateCastExpansion()
{
if (!doesMethodHaveExpandableCasts())
if (!doesMethodHaveExpandableCasts() || opts.OptimizationDisabled())
{
// Nothing to expand in the current method
return PhaseStatus::MODIFIED_NOTHING;
}

if (!opts.IsOptimizedWithProfile())
{
// Currently, we're only interested in expanding cast helpers using profile data
return PhaseStatus::MODIFIED_NOTHING;
}

if (JitConfig.JitConsumeProfileForCasts() == 0)
{
return PhaseStatus::MODIFIED_NOTHING;
}

const bool preferSize = opts.jitFlags->IsSet(JitFlags::JIT_FLAG_SIZE_OPT);
if (preferSize)
{
// The optimization comes with a codegen size increase
JITDUMP("Optimized for size - bail out.\n");
return PhaseStatus::MODIFIED_NOTHING;
}

// TODO-InlineCast: should we still inline some trivial cases even in cold blocks?
const bool skipForRarelyRunBlocks = true;
return fgExpandHelper<&Compiler::fgLateCastExpansionForCall>(skipForRarelyRunBlocks);
Expand All @@ -1862,6 +1843,7 @@ enum class TypeCheckFailedAction
{
ReturnNull,
CallHelper,
CallHelper_Specialized,
CallHelper_AlwaysThrows
};

Expand Down Expand Up @@ -1978,14 +1960,25 @@ static CORINFO_CLASS_HANDLE PickCandidateForTypeCheck(Compiler* com
const bool isCastToExact = comp->info.compCompHnd->isExactType(castToCls);
if (isCastToExact && ((helper == CORINFO_HELP_CHKCASTCLASS) || (helper == CORINFO_HELP_CHKCASTARRAY)))
{
// (string)obj
// (string[])obj
result = castToCls;

// obj is string
// obj is string[]
//
// Fallbacks for these expansions always throw InvalidCastException
*typeCheckFailed = TypeCheckFailedAction::CallHelper_AlwaysThrows;
if ((helper == CORINFO_HELP_CHKCASTCLASS))
{
// (string)obj
//
// Fallback for this expansion always throws InvalidCastException
// TODO: can we do the same for string[]? (importer did not)
*typeCheckFailed = TypeCheckFailedAction::CallHelper_AlwaysThrows;

// Assume that exceptions are rare
*likelihood = 100;

// Assume that exceptions are rare
*likelihood = 100;
// Update the common denominator class to be more exact
*commonCls = result;
}

// We're done, there is no need in consulting with PGO data
}
Expand All @@ -1996,39 +1989,55 @@ static CORINFO_CLASS_HANDLE PickCandidateForTypeCheck(Compiler* com
// obj is string[]
//
// Fallbacks for these expansions simply return null
// TODO: should we keep the helper call for ISINSTANCEOFARRAY like we do for CHKCASTARRAY above?
// The logic is copied from the importer.
*typeCheckFailed = TypeCheckFailedAction::ReturnNull;

// We're done, there is no need in consulting with PGO data
result = castToCls;
}
else
{
CORINFO_CLASS_HANDLE exactClass = NO_CLASS_HANDLE;
// 2) If VM can tell us the exact class for this "cast to" class - use it.
// Just make sure the class is truly exact.
if ((comp->info.compCompHnd->getExactClasses(castToCls, 1, &result) == 1) &&
comp->info.compCompHnd->isExactType(result))
if ((comp->info.compCompHnd->getExactClasses(castToCls, 1, &exactClass) == 1) &&
comp->info.compCompHnd->isExactType(exactClass))
{
if (isCastClass)
result = exactClass;

if ((helper == CORINFO_HELP_CHKCASTINTERFACE) || (helper == CORINFO_HELP_CHKCASTCLASS))
{
// Fallback call is only needed for castclass and only to throw InvalidCastException
*typeCheckFailed = TypeCheckFailedAction::CallHelper_AlwaysThrows;

// Assume that exceptions are rare
*likelihood = 100;

// Update the common denominator class to be more exact
*commonCls = result;
}
else
else if ((helper == CORINFO_HELP_ISINSTANCEOFINTERFACE) || (helper == CORINFO_HELP_ISINSTANCEOFCLASS))
{
// Fallback for isinst simply returns null here
*typeCheckFailed = TypeCheckFailedAction::ReturnNull;
}

// Update the common denominator class to be more exact
*commonCls = result;
// Update the common denominator class to be more exact
*commonCls = result;
}
}
else
{
// 3) Consult with PGO data
LikelyClassMethodRecord likelyClasses[MAX_GDV_TYPE_CHECKS];
unsigned likelyClassCount =
getLikelyClasses(likelyClasses, MAX_GDV_TYPE_CHECKS, comp->fgPgoSchema, comp->fgPgoSchemaCount,
comp->fgPgoData, (int)castHelper->gtCastHelperILOffset);
unsigned likelyClassCount = 0;

if (comp->opts.IsOptimizedWithProfile() && (JitConfig.JitConsumeProfileForCasts() != 0))
{
const int ilOffset = (int)castHelper->gtCastHelperILOffset;
likelyClassCount = getLikelyClasses(likelyClasses, MAX_GDV_TYPE_CHECKS, comp->fgPgoSchema,
comp->fgPgoSchemaCount, comp->fgPgoData, ilOffset);
}

if (likelyClassCount != 0)
{
Expand Down Expand Up @@ -2183,10 +2192,12 @@ static CORINFO_CLASS_HANDLE PickCandidateForTypeCheck(Compiler* com
unreached();
}

if (isCastClass && (result == castToCls) && (*typeCheckFailed == TypeCheckFailedAction::CallHelper))
if ((helper == CORINFO_HELP_CHKCASTCLASS) && (result == castToCls) &&
(*typeCheckFailed == TypeCheckFailedAction::CallHelper))
{
// TODO-InlineCast: Change helper to faster CORINFO_HELP_CHKCASTCLASS_SPECIAL
// it won't check for null and castToCls assuming we've already done it inline.
// A small optimization - use a slightly faster fallback which assumes that we've already checked
// for null and for castToCls itself so it won't do it again.
*typeCheckFailed = TypeCheckFailedAction::CallHelper_Specialized;
}

assert(result != NO_CLASS_HANDLE);
Expand Down Expand Up @@ -2299,6 +2310,12 @@ bool Compiler::fgLateCastExpansionForCall(BasicBlock** pBlock, Statement* stmt,
}
else
{
if (typeCheckFailedAction == TypeCheckFailedAction::CallHelper_Specialized)
{
// A slightly faster fallback which assumes that we've already checked
// for null and for castToCls itself.
call->gtCallMethHnd = eeFindHelper(CORINFO_HELP_CHKCASTCLASS_SPECIAL);
}
GenTree* fallbackTree = gtNewTempStore(tmpNum, call);
fallbackBb = fgNewBBFromTreeAfter(BBJ_ALWAYS, typeCheckBb, fallbackTree, debugInfo, lastBb, true);
}
Expand Down Expand Up @@ -2346,10 +2363,7 @@ bool Compiler::fgLateCastExpansionForCall(BasicBlock** pBlock, Statement* stmt,
//
nullcheckBb->inheritWeight(firstBb);
typeCheckBb->inheritWeightPercentage(nullcheckBb, 50);
fallbackBb->inheritWeightPercentage(typeCheckBb,
(typeCheckFailedAction == TypeCheckFailedAction::CallHelper_AlwaysThrows)
? 0
: 100 - likelihood);
fallbackBb->inheritWeightPercentage(typeCheckBb, fallbackBb->KindIs(BBJ_THROW) ? 0 : 100 - likelihood);
typeCheckSucceedBb->inheritWeightPercentage(typeCheckBb, likelihood);
lastBb->inheritWeight(firstBb);

Expand Down
9 changes: 2 additions & 7 deletions src/coreclr/jit/importer.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5462,7 +5462,6 @@ GenTree* Compiler::impCastClassOrIsInstToTree(

// Pessimistically assume the jit cannot expand this as an inline test
bool canExpandInline = false;
bool partialExpand = false;
bool reversedMTCheck = false;
const CorInfoHelpFunc helper = info.compCompHnd->getCastingHelper(pResolvedToken, isCastClass);

Expand Down Expand Up @@ -5559,7 +5558,7 @@ GenTree* Compiler::impCastClassOrIsInstToTree(
//

GenTree* op2Var = op2;
if (isCastClass && !partialExpand && (exactCls == NO_CLASS_HANDLE))
if (isCastClass && (exactCls == NO_CLASS_HANDLE))
{
// if exactCls is not null we won't have to clone op2 (it will be used only for the fallback)
op2Var = fgInsertCommaFormTemp(&op2);
Expand Down Expand Up @@ -5597,11 +5596,7 @@ GenTree* Compiler::impCastClassOrIsInstToTree(
// use the special helper that skips the cases checked by our inlined cast
specialHelper = CORINFO_HELP_CHKCASTCLASS_SPECIAL;
}
condTrue = gtNewHelperCallNode(specialHelper, TYP_REF, partialExpand ? op2 : op2Var, gtClone(op1));
}
else if (partialExpand)
{
condTrue = gtNewHelperCallNode(helper, TYP_REF, op2, gtClone(op1));
condTrue = gtNewHelperCallNode(specialHelper, TYP_REF, op2Var, gtClone(op1));
}
else
{
Expand Down

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