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Enable GDV with multiple guesses for NativeAOT #87380

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merged 2 commits into from Jun 19, 2023
Merged

Enable GDV with multiple guesses for NativeAOT #87380

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3e46739
Set JitGuardedDevirtualizationMaxTypeChecks for JIT
EgorBo Jun 11, 2023
1ad859d
Address feedback
EgorBo Jun 12, 2023
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22 changes: 22 additions & 0 deletions src/coreclr/jit/compiler.h
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Expand Up @@ -7149,6 +7149,28 @@ class Compiler
unsigned classAttr,
unsigned likelihood);

int getGDVMaxTypeChecks()
{
int typeChecks = JitConfig.JitGuardedDevirtualizationMaxTypeChecks();
if (typeChecks < 0)
{
// Negative value means "it's up to JIT to decide"
if (IsTargetAbi(CORINFO_NATIVEAOT_ABI) && !opts.jitFlags->IsSet(JitFlags::JIT_FLAG_SIZE_OPT))
{
return 3;
}

// We plan to use 3 for CoreCLR too, but we need to make sure it doesn't regress performance
// as CoreCLR heavily relies on Dynamic PGO while for NativeAOT we *usually* don't have it and
// can only perform the "exact" devirtualization.
return 1;
}

// MAX_GDV_TYPE_CHECKS is the upper limit. The constant can be changed, we just suspect that even
// 4 type checks is already too much.
return min(MAX_GDV_TYPE_CHECKS, typeChecks);
}

bool doesMethodHaveExpRuntimeLookup()
{
return (optMethodFlags & OMF_HAS_EXPRUNTIMELOOKUP) != 0;
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6 changes: 3 additions & 3 deletions src/coreclr/jit/importercalls.cpp
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Expand Up @@ -5730,7 +5730,7 @@ void Compiler::pickGDV(GenTreeCall* call,
// Prefer class guess as it is cheaper
if (numberOfClasses > 0)
{
const int maxNumberOfGuesses = min(MAX_GDV_TYPE_CHECKS, JitConfig.JitGuardedDevirtualizationMaxTypeChecks());
const int maxNumberOfGuesses = getGDVMaxTypeChecks();
if (maxNumberOfGuesses == 0)
{
// DOTNET_JitGuardedDevirtualizationMaxTypeChecks=0 means we don't want to do any guarded devirtualization
Expand Down Expand Up @@ -5931,7 +5931,7 @@ void Compiler::considerGuardedDevirtualization(GenTreeCall* call,
{
pickGDV(call, ilOffset, isInterface, likelyClasses, likelyMethodes, &candidatesCount, likelihoods);
assert((unsigned)candidatesCount <= MAX_GDV_TYPE_CHECKS);
assert((unsigned)candidatesCount <= (unsigned)JitConfig.JitGuardedDevirtualizationMaxTypeChecks());
assert((unsigned)candidatesCount <= (unsigned)getGDVMaxTypeChecks());
if (candidatesCount == 0)
{
hasPgoData = false;
Expand All @@ -5944,7 +5944,7 @@ void Compiler::considerGuardedDevirtualization(GenTreeCall* call,
// from both.
if (!hasPgoData && (baseClass != NO_CLASS_HANDLE) && JitConfig.JitEnableExactDevirtualization())
{
int maxTypeChecks = min(JitConfig.JitGuardedDevirtualizationMaxTypeChecks(), MAX_GDV_TYPE_CHECKS);
int maxTypeChecks = min(getGDVMaxTypeChecks(), MAX_GDV_TYPE_CHECKS);

CORINFO_CLASS_HANDLE exactClasses[MAX_GDV_TYPE_CHECKS];
int numExactClasses = info.compCompHnd->getExactClasses(baseClass, MAX_GDV_TYPE_CHECKS, exactClasses);
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4 changes: 2 additions & 2 deletions src/coreclr/jit/jitconfigvalues.h
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Expand Up @@ -527,8 +527,8 @@ CONFIG_INTEGER(JitEnableGuardedDevirtualization, W("JitEnableGuardedDevirtualiza

#define MAX_GDV_TYPE_CHECKS 5
// Number of types to probe for polymorphic virtual call-sites to devirtualize them,
// Max number is MAX_GDV_TYPE_CHECKS defined above ^
CONFIG_INTEGER(JitGuardedDevirtualizationMaxTypeChecks, W("JitGuardedDevirtualizationMaxTypeChecks"), 1)
// Max number is MAX_GDV_TYPE_CHECKS defined above ^. -1 means it's up to JIT to decide
CONFIG_INTEGER(JitGuardedDevirtualizationMaxTypeChecks, W("JitGuardedDevirtualizationMaxTypeChecks"), -1)

// Various policies for GuardedDevirtualization
CONFIG_INTEGER(JitGuardedDevirtualizationChainLikelihood, W("JitGuardedDevirtualizationChainLikelihood"), 0x4B) // 75
Expand Down