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JIT: revise how synthesis treats handler regions #100899

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Merged
AndyAyersMS merged 2 commits into from
Apr 11, 2024
Merged

JIT: revise how synthesis treats handler regions #100899

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JIT: revise how synthesis treats handler regions
AndyAyersMS Apr 11, 2024
f18b0fc
Merge branch 'main' into ReviseExceptionScale
AndyAyersMS Apr 11, 2024
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19 changes: 9 additions & 10 deletions src/coreclr/jit/fgprofilesynthesis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1039,29 +1039,28 @@ void ProfileSynthesis::AssignInputWeights(ProfileSynthesisOption option)

// Determine input weight for EH regions, if any.
//
weight_t exceptionScaleFactor = exceptionScale;
weight_t ehWeight = exceptionWeight;

#ifdef DEBUG
if (JitConfig.JitSynthesisExceptionScale() != nullptr)
if (JitConfig.JitSynthesisExceptionWeight() != nullptr)
{
ConfigDoubleArray JitSynthesisExceptionScaleArray;
JitSynthesisExceptionScaleArray.EnsureInit(JitConfig.JitSynthesisExceptionScale());
weight_t newFactor = JitSynthesisExceptionScaleArray.GetData()[0];
ConfigDoubleArray JitSynthesisExceptionWeightArray;
JitSynthesisExceptionWeightArray.EnsureInit(JitConfig.JitSynthesisExceptionWeight());
weight_t newFactor = JitSynthesisExceptionWeightArray.GetData()[0];

if ((newFactor >= 0) && (newFactor <= 1.0))
{
exceptionScaleFactor = newFactor;
ehWeight = newFactor;
}
}
#endif

JITDUMP("Synthesis: exception scale factor " FMT_WT "\n", exceptionScaleFactor);
const weight_t ehWeight = entryWeight * exceptionScaleFactor;
JITDUMP("Synthesis: exception weight " FMT_WT "\n", ehWeight);

if (ehWeight != 0)
{
// We can't inline methods with EH, also inlinees share the parent
// EH tab, so we can't rely on this being empty.
// We can't inline methods with EH. Inlinees share the parent
// EH tab, so we can't rely on the EH table being empty.
//
if (!m_comp->compIsForInlining())
{
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2 changes: 1 addition & 1 deletion src/coreclr/jit/fgprofilesynthesis.h
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Expand Up @@ -45,7 +45,7 @@ class ProfileSynthesis
{
}

static constexpr weight_t exceptionScale = 0.001;
static constexpr weight_t exceptionWeight = 0.00001;
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@amanasifkhalid amanasifkhalid Apr 11, 2024

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I'm a bit surprised to see this fixed weight is smaller than the scale factor it's replacing. Did you get this number through trial and error, or?

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@AndyAyersMS AndyAyersMS Apr 11, 2024

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Nothing magic here. Just wanted a value that is small enough to ignore in an absolute sense.

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@amanasifkhalid amanasifkhalid Apr 11, 2024

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I see -- so close to zero, but it won't mark the block with BBF_RUN_RARELY.

static constexpr weight_t initialBlendFactor = 0.05;
static constexpr weight_t blendFactorGrowthRate = 3;
static constexpr weight_t cappedLikelihood = 0.999;
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7 changes: 2 additions & 5 deletions src/coreclr/jit/jitconfigvalues.h
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Expand Up @@ -719,18 +719,15 @@ CONFIG_INTEGER(JitRandomlyCollect64BitCounts, W("JitRandomlyCollect64BitCounts")
// 3: profile synthesis for root methods, blend with existing PGO data
CONFIG_INTEGER(JitSynthesizeCounts, W("JitSynthesizeCounts"), 0)

// Check if synthesis left consistent counts
CONFIG_INTEGER(JitCheckSynthesizedCounts, W("JitCheckSynthesizedCounts"), 0)

// If instrumenting the method, run synthesis and save the synthesis results
// as edge or block profile data. Do not actually instrument.
CONFIG_INTEGER(JitPropagateSynthesizedCountsToProfileData, W("JitPropagateSynthesizedCountsToProfileData"), 0)

// Use general (gauss-seidel) solver
CONFIG_INTEGER(JitSynthesisUseSolver, W("JitSynthesisUseSolver"), 1)

// Relative likelihood of exceptions for synthesis
CONFIG_STRING(JitSynthesisExceptionScale, W("JitSynthesisExceptionScale"))
// Weight for exception regions for synthesis
CONFIG_STRING(JitSynthesisExceptionWeight, W("JitSynthesisExceptionWeight"))

// Devirtualize virtual calls with getExactClasses (NativeAOT only for now)
RELEASE_CONFIG_INTEGER(JitEnableExactDevirtualization, W("JitEnableExactDevirtualization"), 1)
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