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Fold BOX+ISINST to null if possible #88989

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merged 9 commits into from
Jul 18, 2023
Merged

Fold BOX+ISINST to null if possible #88989

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f20cc70
Fold BOX+ISINST to null if possible
EgorBo Jul 17, 2023
12dfa1a
Merge branch 'main' of github.com:dotnet/runtime into fold-box-isinst
EgorBo Jul 17, 2023
1ab41bb
Fix return code
EgorBo Jul 17, 2023
dad712e
Ignore Nullable<>
EgorBo Jul 17, 2023
32d113f
add BoxPatterns::IsByRefLike
EgorBo Jul 17, 2023
e6d0d27
Merge branch 'main' of github.com:dotnet/runtime into fold-box-isinst
EgorBo Jul 17, 2023
e57bcea
comment
EgorBo Jul 17, 2023
15fd17e
Merge branch 'main' of github.com:dotnet/runtime into fold-box-isinst
EgorBo Jul 17, 2023
e909754
Update importer.cpp
EgorBo Jul 18, 2023
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21 changes: 21 additions & 0 deletions src/coreclr/jit/importer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2911,6 +2911,27 @@ int Compiler::impBoxPatternMatch(CORINFO_RESOLVED_TOKEN* pResolvedToken,
case CEE_ISINST:
if (codeAddr + 1 + sizeof(mdToken) + 1 <= codeEndp)
{
// First, let's see if we can fold BOX+ISINST to just null if ISINST is known to return null
// for the given argument. Don't make inline observations for this case.
if ((opts != BoxPatterns::MakeInlineObservation) &&
((impStackTop().val->gtFlags & GTF_SIDE_EFFECT) == 0))
{
if ((opts == BoxPatterns::IsByRefLike) ||
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Should we do this for byref-like types? Note that the exact patterns that are supported for them is documented here and I think it is expected that other patterns continue throwing (or, alternatively, that the pattern is documented).

A separate question -- doesn't this logic essentially subsume the logic that happens below?

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@EgorBo EgorBo Jul 18, 2023 •
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A separate question -- doesn't this logic essentially subsume the logic that happens below?

Sort of, in this case we only handle MustNot case while the logic below handles both Must and MustNot - I tried to share them but decided that it's not worth it, also, removed nullable<> support since it didn't add any diffs

Should we do this for byref-like types?

Let me remove it then and keep only the patterns listed there then

(info.compCompHnd->getBoxHelper(pResolvedToken->hClass) == CORINFO_HELP_BOX))
{
CORINFO_RESOLVED_TOKEN isInstTok;
impResolveToken(codeAddr + 1, &isInstTok, CORINFO_TOKENKIND_Casting);
if (info.compCompHnd->compareTypesForCast(pResolvedToken->hClass, isInstTok.hClass) ==
TypeCompareState::MustNot)
{
JITDUMP("\n Importing BOX; ISINST; as null\n");
impPopStack();
impPushOnStack(gtNewNull(), typeInfo(TYP_REF));
return 1 + sizeof(mdToken);
}
}
}

const BYTE* nextCodeAddr = codeAddr + 1 + sizeof(mdToken);

switch (nextCodeAddr[0])
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