[MC/DC][Coverage] Loosen the limit of NumConds from 6 #82448

chapuni · 2024-02-21T00:52:18Z

By storing possible test vectors instead of combinations of conditions, the restriction is dramatically relaxed.

This introduces two options to cc1:

-fmcdc-max-conditions=32767
-fmcdc-max-test-vectors=2147483646

This change makes coverage mapping, profraw, and profdata incompatible with Clang-18.

Bitmap semantics changed. It is incompatible with previous format.
BitmapIdx in Decision points to the end of the bitmap.
Bitmap is packed per function.
llvm-cov can understand profdata generated by llvm-profdata-18.

RFC: https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798

This accept current version of profdata. The output might be different. See also https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798

…de)" This reverts commit d168e0c.

Deprecate `TestVectors`, since no one uses it. This affects the output order of ExecVectors. The current impl emits sorted by binary value of ExecVector. This impl emits along the traversal of `buildTestVector()`.

This accepts current version of profdata. The output might be different. See also https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798

* Split out `Indices[ID][Cond]` * Let `Nodes` debug-only. * Introduce `Offset` * Introduce `HardMaxTVs`

* Sink `TVIdxBuilder` into `mcdc::`. * The ctor accepts `SmallVector<ConditionIDs>` indexed by `ID`. * `class NextIDsBuilder` provides `NextIDs` as`SmallVector<ConditionIDs>`, for `TVIdxBuilder` to use it before `MCDCRecordProcessor()`. It was `BranchParamsMap` or `Map` as `DenseMap<Branch>`. * `NodeIDs` and `Fetcher` function are deprecated.

ornata · 2024-02-21T01:28:32Z

clang/lib/CodeGen/CodeGenPGO.cpp

@@ -983,7 +979,7 @@ void CodeGenPGO::mapRegionCounters(const Decl *D) {
  // for most embedded applications. Setting a maximum value prevents the
  // bitmap footprint from growing too large without the user's knowledge. In
  // the future, this value could be adjusted with a command-line option.
-  unsigned MCDCMaxConditions = (CGM.getCodeGenOpts().MCDCCoverage) ? 6 : 0;
+  unsigned MCDCMaxConditions = (CGM.getCodeGenOpts().MCDCCoverage) ? 32767 : 0;


I think the limit should be controlled by a flag, with a reasonable default value.

E.g.

-mcdc-max-conditions=<value>

MaxCond is one of options. I guess it could be configurable just for theirs coding rules, since I think controlling MaxCond would not make sense.
I know we have to introduce other options as well. I will do later.

MaxCond

MaxTVs to restrict per-expression number of TVs

"Max bytes of bitmap in the CU" to restict inter-function size of the bitmap.

I know you will do this later, but I also wanted to echo the desire for a means to control the condition limit to warn the user against unintended memory footprint expansion, most useful in embedded development contexts. It may not otherwise be obvious to most users what is contributing to larger memory usage. We could also override the default in downstream toolchains.

Also why 32767? Max signed 16-bit value? Is there a reason?

@evodius96 I've introduced -fmcdc-max-conditions=32767.

against unintended memory footprint expansion
I think -fmcdc-max-test-vectors=64 can restrict max bitmap size as the current implementation.

@ornata I have no idea how to determine practical limit for that. So I use SHRT_MAX.

clang/lib/CodeGen/CoverageMappingGen.cpp

llvm/lib/ProfileData/Coverage/CoverageMapping.cpp

clang/lib/CodeGen/CoverageMappingGen.cpp

chapuni

Thanks for your comments and sorry for my hasty w-i-p work . I know a few rough implementations would be there.

clang/lib/CodeGen/CoverageMappingGen.cpp

chapuni · 2024-02-21T07:00:53Z

@hanickadot Your comments to llvm/CoverageMapping.cpp are not for this PR. See #80676 .

They are my preferences.

hanickadot · 2024-02-21T07:09:35Z

@hanickadot Your comments to llvm/CoverageMapping.cpp are not for this PR. See #80676 .

They are my preferences.

Didn't know the context, I saw it green as added. Just ignore it.

clang/docs/SourceBasedCodeCoverage.rst

llvm/docs/LangRef.rst

hanickadot · 2024-06-13T10:08:08Z

clang/lib/CodeGen/CoverageMappingGen.cpp

+    mcdc::TVIdxBuilder Builder(CondIDs);
+    unsigned NumTVs = Builder.NumTestVectors;
+    unsigned MaxTVs = CVM.getCodeGenModule().getCodeGenOpts().MCDCMaxTVs;
+    assert(MaxTVs < mcdc::TVIdxBuilder::HardMaxTVs);


should it be <= or <?

I'm asking because MaxTVs seems like a count, not id

HardMaxTVs(int_max) is actually the error code.

Than I would probably make it !=

3rd arg of `tvbitmap.update` was made unused. Remove 3rd arg. Sweep `condbitmap.update`, since it is no longer used.

zmodem · 2024-06-14T08:48:32Z

This broke the lit tests on mac: https://green.lab.llvm.org/job/llvm.org/job/clang-stage1-RA/1096/

I'll revert to green for now.

This broke the lit tests on Mac: https://green.lab.llvm.org/job/llvm.org/job/clang-stage1-RA/1096/ > By storing possible test vectors instead of combinations of conditions, > the restriction is dramatically relaxed. > > This introduces two options to `cc1`: > > * `-fmcdc-max-conditions=32767` > * `-fmcdc-max-test-vectors=2147483646` > > This change makes coverage mapping, profraw, and profdata incompatible > with Clang-18. > > - Bitmap semantics changed. It is incompatible with previous format. > - `BitmapIdx` in `Decision` points to the end of the bitmap. > - Bitmap is packed per function. > - `llvm-cov` can understand `profdata` generated by `llvm-profdata-18`. > > RFC: > https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798 This reverts commit 7ead2d8.

chapuni · 2024-06-14T09:37:04Z

Oh, it's apple-specific continuous mode test :(

By storing possible test vectors instead of combinations of conditions, the restriction is dramatically relaxed. This introduces two options to `cc1`: * `-fmcdc-max-conditions=32767` * `-fmcdc-max-test-vectors=2147483646` This change makes coverage mapping, profraw, and profdata incompatible with Clang-18. - Bitmap semantics changed. It is incompatible with previous format. - `BitmapIdx` in `Decision` points to the end of the bitmap. - Bitmap is packed per function. - `llvm-cov` can understand `profdata` generated by `llvm-profdata-18`. RFC: https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798 -- Change(s) since llvmorg-19-init-14288-g7ead2d8c7e91 - Update compiler-rt/test/profile/ContinuousSyncMode/image-with-mcdc.c

3rd arg of `tvbitmap.update` was made unused. Remove 3rd arg. Sweep `condbitmap.update`, since it is no longer used.

Mostly apparent changes (#82448, #95496) are described here.

Mostly apparent changes (llvm#82448, llvm#95496) are described here.

By storing possible test vectors instead of combinations of conditions, the restriction is dramatically relaxed. This introduces two options to `cc1`: * `-fmcdc-max-conditions=32767` * `-fmcdc-max-test-vectors=2147483646` This change makes coverage mapping, profraw, and profdata incompatible with Clang-18. - Bitmap semantics changed. It is incompatible with previous format. - `BitmapIdx` in `Decision` points to the end of the bitmap. - Bitmap is packed per function. - `llvm-cov` can understand `profdata` generated by `llvm-profdata-18`. RFC: https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798

[Coverage][MCDC] Adapt mcdc to llvm 19 Related issue: rust-lang#126672 Also finish task 4 at rust-lang#124144 [llvm rust-lang#82448](llvm/llvm-project#82448) has introduced some break changes into mcdc, causing incompatibility between llvm 18 and 19. This draft adapts to that change and gives up supporting for llvm-18.

chapuni added 15 commits February 5, 2024 21:58

Implement MCDCTVIdxBuilder and MCDCTestVectorBuilder (LLVM side)

d168e0c

This accept current version of profdata. The output might be different. See also https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798

Revert "Implement MCDCTVIdxBuilder and MCDCTestVectorBuilder (LLVM si…

35b19ea

…de)" This reverts commit d168e0c.

[Coverage] MCDCRecordProcessor: Find ExecVectors directly

8c777eb

Deprecate `TestVectors`, since no one uses it. This affects the output order of ExecVectors. The current impl emits sorted by binary value of ExecVector. This impl emits along the traversal of `buildTestVector()`.

Merge branch 'mcdc/xv' into HEAD

56042d3

Implement MCDCTVIdxBuilder (LLVM side)

5432aec

This accepts current version of profdata. The output might be different. See also https://discourse.llvm.org/t/rfc-coverage-new-algorithm-and-file-format-for-mc-dc/76798

Update comments and assertions

3ee8a61

Merge remote-tracking branch 'origin/main' into mcdc/tvidx

2fd504a

Reorganize TVIdxBuilder

1f0f3fc

* Split out `Indices[ID][Cond]` * Let `Nodes` debug-only. * Introduce `Offset` * Introduce `HardMaxTVs`

Merge remote-tracking branch 'origin/main' into mcdc/tvidx

06c0801

Merge remote-tracking branch 'origin/main' into HEAD

aa5b2f5

remove <functional>

753d0ad

Update comments.

17cbac7

Add unittest

1a4ffa7

[MC/DC][Coverage] Loosen the limit of NumConds from 6

b5ecfcc

chapuni requested review from MaskRay, ornata, hanickadot and evodius96 February 21, 2024 00:52

ornata reviewed Feb 21, 2024

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hanickadot requested changes Feb 21, 2024

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chapuni commented Feb 21, 2024

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clang/lib/CodeGen/CoverageMappingGen.cpp Outdated Show resolved Hide resolved

clang/lib/CodeGen/CoverageMappingGen.cpp Outdated Show resolved Hide resolved

chapuni changed the base branch from main to users/chapuni/mcdc/tvidx February 21, 2024 13:48

chapuni added 5 commits February 22, 2024 00:00

Update testcases

0ffad9c

Use llvm::sort

c96fd2c

EXPECT_

357a693

Merge branch 'mcdc/tvidx' into HEAD

83d104c

Hide NConds

14c795e

hanickadot reviewed Jun 13, 2024

View reviewed changes

clang/docs/SourceBasedCodeCoverage.rst Outdated Show resolved Hide resolved

llvm/docs/LangRef.rst Show resolved Hide resolved

SourceBasedCodeCoverage.rst: Clarify to be excluded.

450d86b

hanickadot approved these changes Jun 13, 2024

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chapuni merged commit 7ead2d8 into llvm:main Jun 13, 2024
5 of 8 checks passed

chapuni added a commit to chapuni/llvm-project that referenced this pull request Jun 13, 2024

Cleanup MC/DC intrinsics for llvm#82448

80e4ff0

3rd arg of `tvbitmap.update` was made unused. Remove 3rd arg. Sweep `condbitmap.update`, since it is no longer used.

chapuni deleted the mcdc/clangtvidx branch June 13, 2024 12:34

whentojump mentioned this pull request Jun 14, 2024

ld.lld: error: kernel image bigger than KERNEL_IMAGE_SIZE xlab-uiuc/linux-mcdc#5

Open

chapuni added a commit that referenced this pull request Jun 16, 2024

Cleanup MC/DC intrinsics for #82448 (#95496)

85a7bba

3rd arg of `tvbitmap.update` was made unused. Remove 3rd arg. Sweep `condbitmap.update`, since it is no longer used.

chapuni mentioned this pull request Jun 17, 2024

Cleanup MC/DC intrinsics for #82448 #95496

Merged

jpienaar mentioned this pull request Jun 17, 2024

[mlirc] Add missing extern C #95829

Merged

chapuni mentioned this pull request Jun 18, 2024

Update ReleaseNotes for MC/DC changes. #95887

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chapuni added a commit that referenced this pull request Jun 18, 2024

Update ReleaseNotes for MC/DC changes. (#95887)

12cf0dc

Mostly apparent changes (#82448, #95496) are described here.

This was referenced Jun 19, 2024

MC/DC LLVM 19 intrinsics changes rust-lang/rust#126672

Open

[Coverage][MCDC] Prepare MCDC Builder for pattern matching and llvm 19 rust-lang/rust#126677

Closed

[Coverage][MCDC] Adapt mcdc to llvm 19 rust-lang/rust#126733

Open

AlexisPerry pushed a commit to llvm-project-tlp/llvm-project that referenced this pull request Jul 9, 2024

Update ReleaseNotes for MC/DC changes. (llvm#95887)

4e875cc

Mostly apparent changes (llvm#82448, llvm#95496) are described here.

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[MC/DC][Coverage] Loosen the limit of NumConds from 6 #82448

[MC/DC][Coverage] Loosen the limit of NumConds from 6 #82448

chapuni commented Feb 21, 2024 •

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[MC/DC][Coverage] Loosen the limit of NumConds from 6 #82448

[MC/DC][Coverage] Loosen the limit of NumConds from 6 #82448

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