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Late cast expansion: castclass #97237

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merged 4 commits into from
Jan 22, 2024
Merged

Late cast expansion: castclass #97237

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82d6598
Move profiled castclass to late phase
EgorBo Jan 19, 2024
9476e0a
Clean up
EgorBo Jan 19, 2024
e39a62b
Update helperexpansion.cpp
EgorBo Jan 20, 2024
cad2e96
Merge branch 'main' into profiled-castclasses-late
EgorBo Jan 20, 2024
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30 changes: 28 additions & 2 deletions src/coreclr/jit/helperexpansion.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1927,9 +1927,8 @@ static CORINFO_CLASS_HANDLE PickLikelyClass(Compiler* comp, IL_OFFSET offset, un
//
bool Compiler::fgLateCastExpansionForCall(BasicBlock** pBlock, Statement* stmt, GenTreeCall* call)
{
if (!call->IsHelperCall() || !impIsCastHelperMayHaveProfileData(call->GetHelperNum()))
if (!call->IsHelperCall())
{
// Not a cast helper we're interested in
return false;
}

Expand All @@ -1940,6 +1939,26 @@ bool Compiler::fgLateCastExpansionForCall(BasicBlock** pBlock, Statement* stmt,
return false;
}

bool isInstanceOf = false;
switch (call->GetHelperNum())
{
case CORINFO_HELP_ISINSTANCEOFINTERFACE:
case CORINFO_HELP_ISINSTANCEOFARRAY:
case CORINFO_HELP_ISINSTANCEOFCLASS:
case CORINFO_HELP_ISINSTANCEOFANY:
isInstanceOf = true;
break;

case CORINFO_HELP_CHKCASTINTERFACE:
case CORINFO_HELP_CHKCASTARRAY:
case CORINFO_HELP_CHKCASTCLASS:
case CORINFO_HELP_CHKCASTANY:
break;

default:
return false;
}

// Helper calls are never tail calls
assert(!call->IsTailCall());

Expand Down Expand Up @@ -1985,6 +2004,13 @@ bool Compiler::fgLateCastExpansionForCall(BasicBlock** pBlock, Statement* stmt,
return false;
}

if ((castResult == TypeCompareState::MustNot) && !isInstanceOf)
{
// Don't expand castclass if likelyclass always fails the type check
// it's going to throw an exception anyway.
return false;
}

if ((info.compCompHnd->getClassAttribs(likelyCls) & (CORINFO_FLG_INTERFACE | CORINFO_FLG_ABSTRACT)) != 0)
{
// Possible scenario: someone changed Foo to be an interface,
Expand Down
78 changes: 2 additions & 76 deletions src/coreclr/jit/importer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5518,79 +5518,6 @@ GenTree* Compiler::impCastClassOrIsInstToTree(
// If the class is exact, the jit can expand the IsInst check inline.
canExpandInline = isClassExact;
}

// Check if this cast helper have some profile data
// "isinst" with profile data is moved to a late phase.
// The long-term plan is to move all non-trivial expansions there.
if (impIsCastHelperMayHaveProfileData(helper) && isCastClass)
{
const int maxLikelyClasses = 32;
LikelyClassMethodRecord likelyClasses[maxLikelyClasses];
unsigned likelyClassCount =
getLikelyClasses(likelyClasses, maxLikelyClasses, fgPgoSchema, fgPgoSchemaCount, fgPgoData, ilOffset);

if (likelyClassCount > 0)
{
#ifdef DEBUG
for (UINT32 i = 0; i < likelyClassCount; i++)
{
const char* className = eeGetClassName((CORINFO_CLASS_HANDLE)likelyClasses[i].handle);
JITDUMP(" %u) %p (%s) [likelihood:%u%%]\n", i + 1, likelyClasses[i].handle, className,
likelyClasses[i].likelihood);
}

// Optional stress mode to pick a random known class, rather than
// the most likely known class.
if (JitConfig.JitRandomGuardedDevirtualization() != 0)
{
// Reuse the random inliner's random state.
CLRRandom* const random =
impInlineRoot()->m_inlineStrategy->GetRandom(JitConfig.JitRandomGuardedDevirtualization());

unsigned index = static_cast<unsigned>(random->Next(static_cast<int>(likelyClassCount)));
likelyClasses[0].handle = likelyClasses[index].handle;
likelyClasses[0].likelihood = 100;
likelyClassCount = 1;
}
#endif

LikelyClassMethodRecord likelyClass = likelyClasses[0];
CORINFO_CLASS_HANDLE likelyCls = (CORINFO_CLASS_HANDLE)likelyClass.handle;

// if there is a dominating candidate with >= 40% likelihood, use it
const unsigned likelihoodMinThreshold = 40;
if ((likelyCls != NO_CLASS_HANDLE) && (likelyClass.likelihood > likelihoodMinThreshold))
{
TypeCompareState castResult =
info.compCompHnd->compareTypesForCast(likelyCls, pResolvedToken->hClass);

// If case of MustNot we still can optimize isinst (only), e.g.:
//
// bool objIsDisposable = obj is IDisposable;
//
// when the profile tells us that obj is mostly Int32, hence, never implements that interface.
// for castclass it makes little sense as it will always throw a cast exception anyway.
if ((castResult == TypeCompareState::Must) ||
(castResult == TypeCompareState::MustNot && !isCastClass))
{
bool isAbstract = (info.compCompHnd->getClassAttribs(likelyCls) &
(CORINFO_FLG_INTERFACE | CORINFO_FLG_ABSTRACT)) != 0;
// If it's abstract it means we most likely deal with a stale PGO data so bail out.
if (!isAbstract)
{
JITDUMP("Adding \"is %s (%X)\" check as a fast path for %s using PGO data.\n",
eeGetClassName(likelyCls), likelyCls, isCastClass ? "castclass" : "isinst");

reversedMTCheck = castResult == TypeCompareState::MustNot;
canExpandInline = true;
partialExpand = true;
exactCls = likelyCls;
fastPathLikelihood = likelyClass.likelihood;
}
}
}
}
}
}

const bool expandInline = canExpandInline && shouldExpandInline;
Expand Down Expand Up @@ -5621,10 +5548,9 @@ GenTree* Compiler::impCastClassOrIsInstToTree(
compCurBB->SetFlags(BBF_HAS_HISTOGRAM_PROFILE);
}
}
else if (!isCastClass && impIsCastHelperMayHaveProfileData(helper))
else if (impIsCastHelperMayHaveProfileData(helper))
{
// Maybe the late-cast-expand phase will have a better luck expanding this cast.
// TODO: enable for cast-class as well.
// Leave a note for fgLateCastExpand to expand this helper call
call->gtCallMoreFlags |= GTF_CALL_M_CAST_CAN_BE_EXPANDED;
call->gtCastHelperILOffset = ilOffset;
}
Expand Down
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