Remove `LLVMRustCoverageHashCString` #113430

Zalathar · 2023-07-07T07:30:33Z

Coverage has two FFI functions for computing the hash of a byte string. One takes a ptr/len pair (LLVMRustCoverageHashByteArray), and the other takes a NUL-terminated C string (LLVMRustCoverageHashCString).

But on closer inspection, the C string version is unnecessary. The calling-side code converts a Rust &str into a CString, and the C++ code then immediately turns it back into a ptr/len string before actually hashing it. So we can just call the ptr/len version directly instead.

This PR also fixes a bug in the C++ declaration of LLVMRustCoverageHashByteArray. It should be size_t, since that's what is declared and passed on the Rust side, and it's what StrRef's constructor expects to receive on the callee side.

rustbot · 2023-07-07T07:30:40Z

r? @b-naber

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rustbot · 2023-07-07T07:30:43Z

This PR changes how LLVM is built. Consider updating src/bootstrap/download-ci-llvm-stamp.

Zalathar · 2023-07-07T07:30:45Z

@rustbot label +A-code-coverage

Zalathar · 2023-07-07T07:54:25Z

I've tested this locally in two ways:

Before removing the function, I added an assert to verify that both functions give the same result, then ran x test run-coverage.
After switching to just one function, I deliberately corrupted the hash result (via a bitwise not), and ran x test run-coverage again to verify that this causes the tests to fail (since llvm-cov complains about malformed profile data).

Zalathar · 2023-07-07T23:26:45Z

I noticed that the string being hashed also doesn't need to be cloned with to_string, so I've fixed that as well (since it doesn't commute with the rest of this PR).

A symbol already contains a `&str`, and in this context there's no need to make an owned copy, so we can just use the original string reference.

…ector The function body immediately treats it as a slice anyway, so this just makes it possible to call the hash function with arbitrary read-only byte slices.

The Rust-side declaration uses `libc::size_t` for the number of bytes, but the C++ declaration was using `unsigned` instead of `size_t`.

Coverage has two FFI functions for computing the hash of a byte string. One takes a ptr/len pair, and the other takes a NUL-terminated C string. But on closer inspection, the C string version is unnecessary. The calling-side code converts a Rust `&str` into a C string, and the C++ code then immediately turns it back into a ptr/len string before actually hashing it.

b-naber · 2023-07-14T20:26:24Z

@bors r+ rollup

bors · 2023-07-14T20:26:26Z

📌 Commit 352d031 has been approved by b-naber

It is now in the queue for this repository.

bors · 2023-07-15T01:07:39Z

⌛ Testing commit 352d031 with merge acdec7cc8e385d6fbaeb432fac1206829b883586...

bors · 2023-07-15T01:09:46Z

💔 Test failed - checks-actions

rust-log-analyzer · 2023-07-15T01:42:39Z

The job armhf-gnu failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

curl: (22) The requested URL returned error: 404 

error: failed to download llvm from ci

    help: old builds get deleted after a certain time
    help: if trying to compile an old commit of rustc, disable `download-ci-llvm` in config.toml:
    [llvm]
    download-ci-llvm = false
    
Build completed unsuccessfully in 0:00:00

b-naber · 2023-07-15T20:45:26Z

Looks spurious.

@bors r+ rollup

bors · 2023-07-15T20:45:28Z

💡 This pull request was already approved, no need to approve it again.

This pull request previously failed. You should add more commits to fix the bug, or use retry to trigger a build again.
There's another pull request that is currently being tested, blocking this pull request: Remove unneeded handling for ExternalLocation::Unknown in rustdoc render context #113697

bors · 2023-07-15T20:45:29Z

📌 Commit 352d031 has been approved by b-naber

It is now in the queue for this repository.

b-naber · 2023-07-15T20:46:54Z

@bors r-

b-naber · 2023-07-15T20:47:08Z

@bors retry

ehuss · 2023-07-16T01:39:20Z

@bors r=b-naber

bors · 2023-07-16T01:39:21Z

📌 Commit 352d031 has been approved by b-naber

It is now in the queue for this repository.

bors · 2023-07-16T01:56:26Z

⌛ Testing commit 352d031 with merge ffb9b61...

bors · 2023-07-16T03:42:48Z

☀️ Test successful - checks-actions
Approved by: b-naber
Pushing ffb9b61 to master...

rust-timer · 2023-07-16T05:00:49Z

Finished benchmarking commit (ffb9b61): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	2
Improvements ✅ (secondary)	-2.8%	[-3.2%, -2.4%]	6
All ❌✅ (primary)	-0.7%	[-0.7%, -0.7%]	2

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.6%	[-2.1%, -1.2%]	6
All ❌✅ (primary)	2.2%	[2.2%, 2.2%]	2

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 657.636s -> 659.067s (0.22%)

rustbot assigned b-naber Jul 7, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 7, 2023

rustbot added the A-code-coverage Area: Source-based code coverage (-Cinstrument-coverage) label Jul 7, 2023

Zalathar force-pushed the hash branch from d63c38e to 88592de Compare July 7, 2023 23:23

Zalathar force-pushed the hash branch 2 times, most recently from e9666a1 to 8d86dbb Compare July 10, 2023 01:36

Zalathar added 4 commits July 13, 2023 11:16

Don't clone symbol names for coverage hashing

29c53d8

A symbol already contains a `&str`, and in this context there's no need to make an owned copy, so we can just use the original string reference.

Pass a byte slice to coverageinfo::hash_bytes instead of an owned v…

7a5ad35

…ector The function body immediately treats it as a slice anyway, so this just makes it possible to call the hash function with arbitrary read-only byte slices.

Fix the length parameter type of LLVMRustCoverageHashByteArray

7292608

The Rust-side declaration uses `libc::size_t` for the number of bytes, but the C++ declaration was using `unsigned` instead of `size_t`.

Zalathar force-pushed the hash branch from 8d86dbb to 352d031 Compare July 13, 2023 01:31

b-naber approved these changes Jul 14, 2023

View reviewed changes

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 14, 2023

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 15, 2023

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 15, 2023

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 15, 2023

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 15, 2023

bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 16, 2023

bors merged commit ffb9b61 into rust-lang:master Jul 16, 2023

rustbot added this to the 1.73.0 milestone Jul 16, 2023

Zalathar deleted the hash branch July 16, 2023 03:44

Remove LLVMRustCoverageHashCString #113430

Remove LLVMRustCoverageHashCString #113430

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Conversation

Zalathar commented Jul 7, 2023

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rustbot commented Jul 7, 2023

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rustbot commented Jul 7, 2023

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Zalathar commented Jul 7, 2023

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Zalathar commented Jul 7, 2023

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Zalathar commented Jul 7, 2023

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b-naber commented Jul 14, 2023

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bors commented Jul 14, 2023

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bors commented Jul 15, 2023

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bors commented Jul 15, 2023

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rust-log-analyzer commented Jul 15, 2023

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b-naber commented Jul 15, 2023

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bors commented Jul 15, 2023

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bors commented Jul 15, 2023

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b-naber commented Jul 15, 2023

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b-naber commented Jul 15, 2023

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ehuss commented Jul 16, 2023

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bors commented Jul 16, 2023

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bors commented Jul 16, 2023

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bors commented Jul 16, 2023

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rust-timer commented Jul 16, 2023

Overall result: ✅ improvements - no action needed

Instruction count

Max RSS (memory usage)

Cycles

Binary size

Uh oh!

Uh oh!

Remove `LLVMRustCoverageHashCString` #113430

Remove `LLVMRustCoverageHashCString` #113430