Allow custom default address spaces and parse `p-` specifications in the datalayout string #143182

xdoardo · 2025-06-29T10:17:45Z

Some targets, such as CHERI, use as default an address space different from the "normal" default address space 0 (in the case of CHERI, 200 is used). Currently, rustc does not allow to specify custom address spaces and does not take into consideration p- specifications in the datalayout string.

This patch tries to mitigate these problems by allowing targets to define a custom default address space (while keeping the default value to address space 0) and adding the code to parse the p- specifications in rustc_abi. The main changes are that TargetDataLayout now uses functions to refer to pointer-related informations, instead of having specific fields for the size and alignment of pointers in the default address space; furthermore, the two pointer_size and pointer_align fields in TargetDataLayout are replaced with an FxHashMap that holds info for all the possible address spaces, as parsed by the p- specifications.

The potential performance drawbacks of not having ad-hoc fields for the default address space will be tested in this PR's CI run.

r? workingjubilee

rustbot · 2025-06-29T10:17:50Z

workingjubilee is currently at their maximum review capacity.
They may take a while to respond.

rustbot · 2025-06-29T10:17:52Z

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

These commits modify compiler targets.
(See the Target Tier Policy.)

Some changes occurred in compiler/rustc_ast_lowering/src/format.rs

cc @m-ou-se

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

Some changes occurred in cfg and check-cfg configuration

cc @Urgau

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

workingjubilee · 2025-06-29T10:28:43Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-29T10:28:47Z

⌛ Trying commit ef6e4ef with merge a6d8fc2…

To cancel the try build, run the command @bors2 try cancel.

Allow custom default address spaces and parse `p-` specifications in the datalayout string Some targets, such as CHERI, use as default an address space different from the "normal" default address space `0` (in the case of CHERI, [200 is used](https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-877.pdf)). Currently, `rustc` does not allow to specify custom address spaces and does not take into consideration [`p-` specifications in the datalayout string](https://llvm.org/docs/LangRef.html#langref-datalayout). This patch tries to mitigate these problems by allowing target to define a custom default address space (while keeping the default value to address space `0`) and adding the code to parse the `p-` specifications in `rustc_abi`. The main changes are that `TargetDataLayout` now uses functions to refer to pointer-related informations, instead of having specific fields for the size and alignment of pointers in the default address space: the potential performance drawbacks of not having ad-hoc fields will be tested in this PR's CI run. r? workingjubilee

rust-bors · 2025-06-29T12:47:13Z

☀️ Try build successful (CI)
Build commit: a6d8fc2 (a6d8fc279459764136b16847f5b4411d4298525d, parent: 5ca574e85b67cec0a6fc3fddfe398cbe676c9c69)

rust-timer · 2025-06-29T14:13:30Z

Finished benchmarking commit (a6d8fc2): comparison URL.

Overall result: ❌ regressions - 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)	1.0%	[0.7%, 1.7%]	8
Regressions ❌ (secondary)	2.0%	[0.9%, 4.7%]	38
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.0%	[0.7%, 1.7%]	8

Max RSS (memory usage)

Results (primary -2.6%, secondary -8.0%)

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
Improvements ✅ (primary)	-2.6%	[-3.6%, -1.5%]	2
Improvements ✅ (secondary)	-8.0%	[-8.0%, -8.0%]	1
All ❌✅ (primary)	-2.6%	[-3.6%, -1.5%]	2

Cycles

Results (secondary 2.6%)

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)	2.6%	[2.4%, 2.7%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 695.013s -> 695.668s (0.09%)
Artifact size: 371.77 MiB -> 372.01 MiB (0.06%)

rustbot · 2025-06-29T17:34:17Z

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

workingjubilee · 2025-06-29T20:27:21Z

@bors2 try

rust-bors · 2025-06-29T20:27:25Z

⌛ Trying commit fce06e3 with merge 92687cf…

To cancel the try build, run the command @bors2 try cancel.

Allow custom default address spaces and parse `p-` specifications in the datalayout string Some targets, such as CHERI, use as default an address space different from the "normal" default address space `0` (in the case of CHERI, [200 is used](https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-877.pdf)). Currently, `rustc` does not allow to specify custom address spaces and does not take into consideration [`p-` specifications in the datalayout string](https://llvm.org/docs/LangRef.html#langref-datalayout). This patch tries to mitigate these problems by allowing targets to define a custom default address space (while keeping the default value to address space `0`) and adding the code to parse the `p-` specifications in `rustc_abi`. The main changes are that `TargetDataLayout` now uses functions to refer to pointer-related informations, instead of having specific fields for the size and alignment of pointers in the default address space; furthermore, the two `pointer_size` and `pointer_align` fields in `TargetDataLayout` are replaced with an `FxHashMap` that holds info for all the possible address spaces, as parsed by the `p-` specifications. The potential performance drawbacks of not having ad-hoc fields for the default address space will be tested in this PR's CI run. r? workingjubilee

rust-bors · 2025-06-29T22:43:09Z

☀️ Try build successful (CI)
Build commit: 92687cf (92687cf86ed4b58afb2653d78a1c735272295f02, parent: ed2d759783dc9de134bbb3f01085b1e6dbf539f3)

workingjubilee · 2025-06-30T06:53:02Z

@rust-timer build 92687cf

rust-timer · 2025-06-30T09:01:27Z

Finished benchmarking commit (92687cf): comparison URL.

Overall result: ❌ regressions - 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)	0.4%	[0.4%, 0.6%]	4
Regressions ❌ (secondary)	1.1%	[0.3%, 1.9%]	29
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[0.4%, 0.6%]	4

Max RSS (memory usage)

Results (primary -2.3%, 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)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-2.3%	[-3.1%, -1.4%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.3%	[-3.1%, -1.4%]	2

Cycles

Results (primary -1.1%, secondary 0.3%)

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)	1.9%	[1.9%, 1.9%]	1
Improvements ✅ (primary)	-1.1%	[-1.2%, -0.9%]	2
Improvements ✅ (secondary)	-1.2%	[-1.2%, -1.2%]	1
All ❌✅ (primary)	-1.1%	[-1.2%, -0.9%]	2

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%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 694.715s -> 695.8s (0.16%)
Artifact size: 371.77 MiB -> 371.86 MiB (0.02%)

workingjubilee · 2025-07-05T22:06:58Z

quickly trying the usual culprits of rejections

@bors2 try jobs=test-various,armhf-gnu,i686-gnu-1,i686-msvc-1,x86_64-msvc-1

rust-bors · 2025-07-05T22:07:01Z

⌛ Trying commit 9701efb with merge 03c8605…

To cancel the try build, run the command @bors2 try cancel.

Allow custom default address spaces and parse `p-` specifications in the datalayout string Some targets, such as CHERI, use as default an address space different from the "normal" default address space `0` (in the case of CHERI, [200 is used](https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-877.pdf)). Currently, `rustc` does not allow to specify custom address spaces and does not take into consideration [`p-` specifications in the datalayout string](https://llvm.org/docs/LangRef.html#langref-datalayout). This patch tries to mitigate these problems by allowing targets to define a custom default address space (while keeping the default value to address space `0`) and adding the code to parse the `p-` specifications in `rustc_abi`. The main changes are that `TargetDataLayout` now uses functions to refer to pointer-related informations, instead of having specific fields for the size and alignment of pointers in the default address space; furthermore, the two `pointer_size` and `pointer_align` fields in `TargetDataLayout` are replaced with an `FxHashMap` that holds info for all the possible address spaces, as parsed by the `p-` specifications. The potential performance drawbacks of not having ad-hoc fields for the default address space will be tested in this PR's CI run. r? workingjubilee try-job: test-various try-job: armhf-gnu try-job: i686-gnu-1 try-job: i686-msvc-1 try-job: x86_64-msvc-1

rust-bors · 2025-07-06T00:43:55Z

☀️ Try build successful (CI)
Build commit: 03c8605 (03c8605a59703578ccb6a8297428f108fb1fec96, parent: 175e04331be56c5b4bdf77478434b1a5e0556770)

…custom default data address space

xdoardo · 2025-07-07T09:42:59Z

@rustbot label -S-waiting-on-author +S-waiting-on-review

workingjubilee · 2025-07-07T10:07:45Z

@bors r+

bors · 2025-07-07T10:07:48Z

📌 Commit 93f1201 has been approved by workingjubilee

It is now in the queue for this repository.

bors · 2025-07-07T17:28:18Z

⌛ Testing commit 93f1201 with merge 2f8eeb2...

bors · 2025-07-07T18:23:13Z

☔ The latest upstream changes (presumably #143582) made this pull request unmergeable. Please resolve the merge conflicts.

workingjubilee · 2025-07-07T19:10:03Z

bitrotty.

@bors rollup=iffy p=1

bors · 2025-07-07T20:29:44Z

☀️ Test successful - checks-actions
Approved by: workingjubilee
Pushing 2f8eeb2 to master...

github-actions · 2025-07-07T20:32:37Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 1b0bc59 (parent) -> 2f8eeb2 (this PR)

Test differences

Show 3 test diffs

3 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 2f8eeb2bba86b8f457ec602c578473c711f85628 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-apple-various: 7932.5s -> 5516.0s (-30.5%)
x86_64-apple-1: 6904.1s -> 8544.1s (23.8%)
x86_64-mingw-1: 10358.2s -> 8583.5s (-17.1%)
x86_64-apple-2: 6156.3s -> 6784.3s (10.2%)
dist-sparcv9-solaris: 5475.3s -> 4940.6s (-9.8%)
dist-armhf-linux: 5217.2s -> 4736.9s (-9.2%)
dist-x86_64-msvc-alt: 8165.4s -> 8872.2s (8.7%)
dist-powerpc-linux: 5365.8s -> 4924.6s (-8.2%)
x86_64-gnu-llvm-20-3: 7442.9s -> 6834.5s (-8.2%)
dist-x86_64-apple: 9821.2s -> 9072.3s (-7.6%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-07-07T21:39:02Z

Finished benchmarking commit (2f8eeb2): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -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
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 2.4%, secondary -1.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.4%	[1.2%, 3.6%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.9%	[-1.9%, -1.9%]	1
All ❌✅ (primary)	2.4%	[1.2%, 3.6%]	2

Cycles

Results (primary 4.1%, secondary -0.8%)

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

	mean	range	count
Regressions ❌ (primary)	4.1%	[4.1%, 4.1%]	1
Regressions ❌ (secondary)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.6%	[-3.6%, -3.6%]	1
All ❌✅ (primary)	4.1%	[4.1%, 4.1%]	1

Binary size

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

Bootstrap: 464.431s -> 465.909s (0.32%)
Artifact size: 372.18 MiB -> 372.26 MiB (0.02%)

rustbot assigned workingjubilee Jun 29, 2025

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 29, 2025

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jun 29, 2025

xdoardo force-pushed the more-addrspace branch from ef6e4ef to fce06e3 Compare June 29, 2025 17:34

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compiler: Parse p- specs in datalayout string, allow definition of …

93f1201

…custom default data address space

xdoardo force-pushed the more-addrspace branch from 9701efb to 93f1201 Compare July 7, 2025 07:04

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 7, 2025

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 7, 2025

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 7, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 7, 2025

bors merged commit 2f8eeb2 into rust-lang:master Jul 7, 2025
12 checks passed

rustbot added this to the 1.90.0 milestone Jul 7, 2025

This was referenced Jul 7, 2025

Move all LLVM externs into the rustc_llvm crate #142897

Open

Move scalar_to_backend to ssa #142960

Open

Allow custom default address spaces and parse p- specifications in the datalayout string #143182

Allow custom default address spaces and parse p- specifications in the datalayout string #143182

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Overall result: ❌ regressions - please read the text below

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Overall result: ❌ regressions - please read the text below

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Test differences

Job duration changes

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rust-timer commented Jul 7, 2025

Overall result: ❌ regressions - no action needed

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Allow custom default address spaces and parse `p-` specifications in the datalayout string #143182

Allow custom default address spaces and parse `p-` specifications in the datalayout string #143182

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