Tell LLVM about read-only captures

[nikic]

&Freeze parameters are not only readonly within the function, but any captures of the pointer can also only be used for reads. This can now be encoded using the captures(address, read_provenance) attribute.

r? ghost

[nikic]

@bors try @rust-timer queue

[rust-log-analyzer]

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

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

All checks passed!
checking python file formatting
27 files already formatted
checking C++ file formatting
/checkout/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp:437:47: error: code should be clang-formatted [-Wclang-format-violations]
    return wrap(Attribute::getWithCaptureInfo(*unwrap(C),
                                              ^
/checkout/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp:437:58: error: code should be clang-formatted [-Wclang-format-violations]
    return wrap(Attribute::getWithCaptureInfo(*unwrap(C),
                                                         ^
/checkout/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp:438:57: error: code should be clang-formatted [-Wclang-format-violations]
                CaptureInfo(CaptureComponents::Address |
                                                        ^

clang-format linting failed! Printing diff suggestions:
--- /checkout/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp (actual)
+++ /checkout/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp (formatted)
@@ -433,11 +433,11 @@
   if (RustAttr == LLVMRustAttributeKind::NoCapture) {
     return wrap(Attribute::getWithCaptureInfo(*unwrap(C), CaptureInfo::none()));
   }
   if (RustAttr == LLVMRustAttributeKind::CapturesReadOnly) {
-    return wrap(Attribute::getWithCaptureInfo(*unwrap(C),
-                CaptureInfo(CaptureComponents::Address |
-                            CaptureComponents::ReadProvenance)));
+    return wrap(Attribute::getWithCaptureInfo(
+        *unwrap(C), CaptureInfo(CaptureComponents::Address |
+                                CaptureComponents::ReadProvenance)));
   }
 #endif
   return wrap(Attribute::get(*unwrap(C), fromRust(RustAttr)));
 }

some tidy checks failed
tidy error: checks with external tool 'clang-format' failed
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/rust-tidy /checkout /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo /checkout/obj/build 4 /node/bin/npm --extra-checks=py,cpp,js` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1634:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1239:29

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:01:16
  local time: Mon Aug 11 16:10:15 UTC 2025
  network time: Mon, 11 Aug 2025 16:10:15 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[rust-bors]

☀️ Try build successful (CI)
Build commit: 6bc3793 (6bc37934c6eaa84bfd300c54189bec62e15d42ed, parent: 577166503aee7290e09374da21f4045c455acfd5)

[rust-timer]

Finished benchmarking commit (6bc3793): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.3%, 0.4%]	5
Regressions ❌ (secondary)	1.0%	[0.9%, 1.6%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.8%	[-0.8%, -0.7%]	5
All ❌✅ (primary)	0.3%	[0.3%, 0.4%]	5

Max RSS (memory usage)

Results (secondary 3.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.9%	[3.9%, 3.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -2.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-	-	0

Binary size

Results (secondary 0.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	23
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 465.465s -> 464.036s (-0.31%)
Artifact size: 377.33 MiB -> 377.30 MiB (-0.01%)