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Fix VN incorrect optimizations with a new JitEEInterface function. #57282

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Merged
sandreenko merged 10 commits into from
Aug 24, 2021
Merged

Fix VN incorrect optimizations with a new JitEEInterface function. #57282

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d579fe5
Add/return tests.
Aug 10, 2021
56361dd
improve the test naming.
Aug 12, 2021
f239a37
Add a new JitEE method.
Aug 12, 2021
f40a7dc
Handle generically dissimilar type concerns as well as handle derived…
davidwrighton Aug 13, 2021
fb0e901
Fix the field and Unsafe issues.
Aug 12, 2021
17432ca
fix some failures.
Aug 16, 2021
34c4edb
Fix an oooold bug in VN.
Aug 16, 2021
a4add9d
Add new test cases and a fix for them.
Aug 16, 2021
fe65446
correct a test copy paste
Aug 16, 2021
e438e3d
response review.
Aug 23, 2021
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Handle generically dissimilar type concerns as well as handle derived… 
… type case in the managed compiler
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@davidwrighton
davidwrighton authored and Sergey committed Aug 24, 2021
commit f40a7dc12f4114adc52b28a706bf197a5120f321
34 changes: 32 additions & 2 deletions src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3533,8 +3533,38 @@ private uint getExpectedTargetArchitecture()

private bool doesFieldBelongToClass(CORINFO_FIELD_STRUCT_* fld, CORINFO_CLASS_STRUCT_* cls)
{
// we need it to return true for both canon and not-canon classes.
return (HandleToObject(fld).OwningType == HandleToObject(cls));
var field = HandleToObject(fld);
var queryType = HandleToObject(cls);

Debug.Assert(!field.IsStatic);

// doesFieldBelongToClass implements the predicate of...
// if field is not associated with the class in any way, return false.
// if field is the only FieldDesc that the JIT might see for a given class handle
// and logical field pair then return true. This is needed as the field handle here
// is used as a key into a hashtable mapping writes to fields to value numbers.
//
// In this implmentation this is made more complex as the JIT is exposed to CORINFO_FIELD_STRUCT
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@AndyAyersMS AndyAyersMS Aug 16, 2021

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Maybe make it clearer that the crossgen2 behavior is different than the runtime behavior?

Is this something we should fix down the road? Seems like it would make us more conservative in places when doing R2R codegen.

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@sandreenko sandreenko Aug 22, 2021

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Maybe make it clearer that the crossgen2 behavior is different than the runtime behavior?

I will add a comment.

Is this something we should fix down the road? Seems like it would make us more conservative in places when doing R2R codegen.

I hope we will target to get rid of FldSeq and its dependency on FIELD_HANDLE and STRUCT_HANDLE.

If not we can do:

if (crossgen2)
{
 canonFieldHandle = JitEEInterface::getCanonField(fieldHandle);
  bool doesBelong = JitEEInterface::doesFieldBelongToClass(canonFieldHandle , clsHnd);
}

but I don't like such a solution, it hammers JIT to VM behavior, we can do it always, not only for crossgen2, but then it is an unnecessary VM call.

// pointers which represent exact instantions, so performing exact matching is the necessary approach

// BaseType._field, BaseType -> true
// BaseType._field, DerivedType -> true
// BaseType<__Canon>._field, BaseType<__Canon> -> true
// BaseType<__Canon>._field, BaseType<string> -> false
// BaseType<__Canon>._field, BaseType<object> -> false
// BaseType<sbyte>._field, BaseType<sbyte> -> true
// BaseType<sbyte>._field, BaseType<byte> -> false

var fieldOwnerType = field.OwningType;

while (queryType != null)
{
if (fieldOwnerType == queryType)
return true;
queryType = queryType.BaseType;
}

return false;
}

private bool isMethodDefinedInCoreLib()
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27 changes: 24 additions & 3 deletions src/coreclr/vm/jitinterface.cpp
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Expand Up @@ -11480,8 +11480,8 @@ bool CEEJitInfo::doesFieldBelongToClass(CORINFO_FIELD_HANDLE fldHnd, CORINFO_CLA
{
CONTRACTL {
THROWS;
GC_TRIGGERS;
MODE_PREEMPTIVE;
GC_TRIGGERS;
MODE_PREEMPTIVE;
} CONTRACTL_END;

bool result;
Expand All @@ -11491,8 +11491,29 @@ bool CEEJitInfo::doesFieldBelongToClass(CORINFO_FIELD_HANDLE fldHnd, CORINFO_CLA
FieldDesc* field = (FieldDesc*) fldHnd;
TypeHandle th(cls);

_ASSERTE(!field->IsStatic());

// doesFieldBelongToClass implements the predicate of...
// if field is not associated with the class in any way, return false.
// if field is the only FieldDesc that the JIT might see for a given class handle
// and logical field pair then return true. This is needed as the field handle here
// is used as a key into a hashtable mapping writes to fields to value numbers.
//
// In the CoreCLR VM implementation, verifying that the canonical MethodTable of
// the field matches the type found via GetExactDeclaringType, as all instance fields
// are only held on the canonical MethodTable.
// This yields a truth table such as

// BaseType._field, BaseType -> true
// BaseType._field, DerivedType -> true
// BaseType<__Canon>._field, BaseType<__Canon> -> true
// BaseType<__Canon>._field, BaseType<string> -> true
// BaseType<__Canon>._field, BaseType<object> -> true
// BaseType<sbyte>._field, BaseType<sbyte> -> true
// BaseType<sbyte>._field, BaseType<byte> -> false

MethodTable* pMT = field->GetExactDeclaringType(th.GetMethodTable());
result = (pMT != nullptr);
result = (pMT != nullptr) && (pMT->GetCanonicalMethodTable() == field->GetApproxEnclosingMethodTable()->GetCanonicalMethodTable());

EE_TO_JIT_TRANSITION();

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