[x64][SysV] Classify empty structs for passing like padding - #103799

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[x64][SysV] Classify empty structs for passing like padding#103799
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tomeksowi:sysv-empty-struct-passing

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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:

NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.

Stems from #101796, part of #84834, cc @dotnet/samsung

@tomeksowi
Classify empty structs on x64 like padding
aba87b6
The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
@tomeksowi
Add comment to fix JIT to AssignClassifiedEightByteTypes
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place

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Comment threadsrc/coreclr/vm/methodtable.cpp
// then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
// so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
//
// TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.

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Do you plan to fix this TODO in this PR?

@tomeksowitomeksowiJun 21, 2024•
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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.

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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place

Sure, I'll lift a couple from #101796.

EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.
EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.

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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).

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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
// then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
// so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
//
// TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.

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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.

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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).

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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.

Meanwhile this smaller fix is ready for review.

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Does this fix handle the significant padding cases correctly (i.e. as before this change)?

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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.

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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?

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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?

Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.

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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying

Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.

@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?

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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?

Yes. I do not see a problem with the ABI change here.

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Thanks!

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[x64][SysV] Classify empty structs for passing like padding - #103799
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tomeksowi:sysv-empty-struct-passing
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[x64][SysV] Classify empty structs for passing like padding#103799
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:
NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.
Stems from #101796, part of #84834, cc @dotnet/samsung
@tomeksowi
Classify empty structs on x64 like padding
aba87b6
The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
@tomeksowi
Add comment to fix JIT to AssignClassifiedEightByteTypes
131a3c5
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
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Comment threadsrc/coreclr/vm/methodtable.cpp
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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Do you plan to fix this TODO in this PR?
@tomeksowitomeksowiJun 21, 2024•

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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
Sure, I'll lift a couple from #101796.
EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.

EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.
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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).
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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.
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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).
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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.
Meanwhile this smaller fix is ready for review.
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Does this fix handle the significant padding cases correctly (i.e. as before this change)?
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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.
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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying
Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.
@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
Yes. I do not see a problem with the ABI change here.
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Thanks!
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[x64][SysV] Classify empty structs for passing like padding - #103799
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tomeksowi:sysv-empty-struct-passing
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[x64][SysV] Classify empty structs for passing like padding#103799
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:
NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.
Stems from #101796, part of #84834, cc @dotnet/samsung
@tomeksowi
Classify empty structs on x64 like padding
aba87b6
The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
@tomeksowi
Add comment to fix JIT to AssignClassifiedEightByteTypes
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
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Comment threadsrc/coreclr/vm/methodtable.cpp
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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Do you plan to fix this TODO in this PR?
@tomeksowitomeksowiJun 21, 2024•

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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
Sure, I'll lift a couple from #101796.
EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.

EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.
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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).
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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.
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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).
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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.
Meanwhile this smaller fix is ready for review.
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Does this fix handle the significant padding cases correctly (i.e. as before this change)?
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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.
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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying
Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.
@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
Yes. I do not see a problem with the ABI change here.
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[x64][SysV] Classify empty structs for passing like padding - #103799
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[x64][SysV] Classify empty structs for passing like padding#103799
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:
NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.
Stems from #101796, part of #84834, cc @dotnet/samsung
@tomeksowi
Classify empty structs on x64 like padding
aba87b6
The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
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Add comment to fix JIT to AssignClassifiedEightByteTypes
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
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Comment threadsrc/coreclr/vm/methodtable.cpp
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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Do you plan to fix this TODO in this PR?
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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
Sure, I'll lift a couple from #101796.
EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.

EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.
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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).
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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.
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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).
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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.
Meanwhile this smaller fix is ready for review.
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Does this fix handle the significant padding cases correctly (i.e. as before this change)?
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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.
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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying
Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.
@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
Yes. I do not see a problem with the ABI change here.
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Thanks!
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injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
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[x64][SysV] Classify empty structs for passing like padding - #103799
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:
NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.
Stems from #101796, part of #84834, cc @dotnet/samsung
@tomeksowi
Classify empty structs on x64 like padding
aba87b6
The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
@tomeksowi
Add comment to fix JIT to AssignClassifiedEightByteTypes
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
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Comment threadsrc/coreclr/vm/methodtable.cpp
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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Do you plan to fix this TODO in this PR?
@tomeksowitomeksowiJun 21, 2024•

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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
Sure, I'll lift a couple from #101796.
EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.

EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.
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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).
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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.
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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).
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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.
Meanwhile this smaller fix is ready for review.
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Does this fix handle the significant padding cases correctly (i.e. as before this change)?
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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.
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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying
Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.
@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
Yes. I do not see a problem with the ABI change here.
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[x64][SysV] Classify empty structs for passing like padding - #103799
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[x64][SysV] Classify empty structs for passing like padding#103799
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:
NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.
Stems from #101796, part of #84834, cc @dotnet/samsung
@tomeksowi
Classify empty structs on x64 like padding
aba87b6
The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
@tomeksowi
Add comment to fix JIT to AssignClassifiedEightByteTypes
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
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Comment threadsrc/coreclr/vm/methodtable.cpp
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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Do you plan to fix this TODO in this PR?
@tomeksowitomeksowiJun 21, 2024•

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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
Sure, I'll lift a couple from #101796.
EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.

EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.
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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).
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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.
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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).
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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.
Meanwhile this smaller fix is ready for review.
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Does this fix handle the significant padding cases correctly (i.e. as before this change)?
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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.
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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying
Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.
@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
Yes. I do not see a problem with the ABI change here.
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Thanks!
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injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
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[x64][SysV] Classify empty structs for passing like padding - #103799
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tomeksowi:sysv-empty-struct-passing
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[x64][SysV] Classify empty structs for passing like padding#103799
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:
NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.
Stems from #101796, part of #84834, cc @dotnet/samsung
@tomeksowi
Classify empty structs on x64 like padding
aba87b6
The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
@tomeksowi
Add comment to fix JIT to AssignClassifiedEightByteTypes
131a3c5
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
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Comment threadsrc/coreclr/vm/methodtable.cpp
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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Do you plan to fix this TODO in this PR?
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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
Sure, I'll lift a couple from #101796.
EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.

EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.
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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).
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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.
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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).
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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.
Meanwhile this smaller fix is ready for review.
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Does this fix handle the significant padding cases correctly (i.e. as before this change)?
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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.
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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying
Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.
@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
Yes. I do not see a problem with the ABI change here.
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Thanks!
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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[x64][SysV] Classify empty structs for passing like padding - #103799
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tomeksowi:sysv-empty-struct-passing
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[x64][SysV] Classify empty structs for passing like padding#103799
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tomeksowi:sysv-empty-struct-passing
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the behavior of GCC & Clang on Linux and the System V ABI which says:
NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and empty structures and unions.
Stems from #101796, part of #84834, cc @dotnet/samsung
@tomeksowi
Classify empty structs on x64 like padding
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The current implementation barred a struct containing empty struct fields from enregistration. This did not match the [System V ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf) which says "NO_CLASS This class is used as initializer in the algorithms. It will be used for padding and **empty structures** and unions". It also does not match the behavior of GCC & Clang on Linux.
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Add comment to fix JIT to AssignClassifiedEightByteTypes
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
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cc @dotnet/jit-contrib @jakobbotsch
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Comment threadsrc/coreclr/vm/methodtable.cpp
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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Do you plan to fix this TODO in this PR?
@tomeksowitomeksowiJun 21, 2024•

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No. It would require going through the JIT like I did in #101796 for RISC-V and fix in many places. Right now my priority is on RISC-V but when I'm done with #101796 I can revisit it. By then @jakobbotsch's ongoing effort to centralize ABI passing infos will probably be more advanced, which will also facilitate fixing x64.
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Could you please add some tests? src\tests\JIT\Directed\StructABI looks like a good place
Sure, I'll lift a couple from #101796.
EDIT: In fact, I think I can lift the entire test suite and disable Empty8Float tests on System V.

EDIT2: I added some dedicated tests for System V after all, RISC-V will be added in subsequent PRs.
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I think the GC\Scenarios\RanCollect\rancollect\rancollect.cmd time-out on Windows x64 is not related to this change (which is System V only).
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Comment threadsrc/coreclr/tools/Common/JitInterface/SystemVStructClassificator.cs
 // then the classification of this eightbyte might be NoClass. We can't hand a classification of NoClass to the JIT
 // so set the class to Integer (as though the struct has a char[8] padding) if the class is NoClass.
 //
 // TODO: Fix JIT, NoClass eightbytes are valid and passing them is broken because of this.
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What does the difference between NoClass and something like char[8] end up being? For significant padding (structs with explicit layout) it seems like we have to consider them to be the same or things will end up odd/wrong.
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char[8] is an INTEGER eightbyte which gets assigned an integer register for passing; a NO_CLASS eightbyte doesn't get any register. Passing on the stack is the same, though (NO_CLASS padding does take up space).
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Opened #104098 as I'll need an URL for ActiveIssue in tests in future PRs.
Meanwhile this smaller fix is ready for review.
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Does this fix handle the significant padding cases correctly (i.e. as before this change)?
@tomeksowitomeksowiJun 27, 2024

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It should, the NO_CLASS -> INTEGER eightbyte reclassification is still there. And I didn't see any CLR tests (prio1) go off on Checked build, assuming there are tests for significant padding by now.
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
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It looks like there's a bunch of asm diffs with this change, can you take a look at whether they are expected?
Thanks for running the bot. Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying. I'll look at it in spare time between RISC-V PRs.
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Diffs are to be expected, some arguments which used to be passed by reference are now enregistered but large amount of performance regressions are worrying
Note that they are size diffs only, and overall the size improves. I spot checked a few of the regressions and it's usually the result of some new register shuffling because of an empty struct now taking up a register, so I guess those diffs are overall expected. Some of these cases look like they could be switched to static abstracts to avoid the parameter entirely.
@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
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@jkotas I assume we are ok to take an ABI change like this one since the R2R format is already being bumped?
Yes. I do not see a problem with the ABI change here.
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Thanks!
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