Emit warning when calling/declaring functions with unavailable vectors. #132173

veluca93 · 2024-10-26T07:37:46Z

On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.)

As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code.

This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI.

See the nomination comment for more discussion.

Part of #116558

r? RalfJung

jieyouxu · 2024-10-26T09:01:21Z

@bors try @rust-timer queue

Emit warning when calling/declaring functions with unavailable vectors. On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.) As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code. This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI. See the [nomination comment](rust-lang#127731 (comment)) for more discussion. Part of rust-lang#116558 r? RalfJung

bors · 2024-10-26T09:02:33Z

⌛ Trying commit 4526613 with merge bbf9ed8...

RalfJung · 2024-10-26T09:13:36Z

The collector always runs, so likely we'll have to make this new check a query to avoid the perf issues.

For the declaration-site check this should be fairly easy, we can pass in the monomorphized instance and that has everything we need. The call-site check is more tricky since the inputs currently are (callee_ty, *fn_span, self.body.source.instance). AFAIK we usually avoid passing a span into a query as those are quite unstable, but not sure what else to do here?
Cc @compiler-errors

bors · 2024-10-26T10:56:30Z

☀️ Try build successful - checks-actions
Build commit: bbf9ed8 (bbf9ed8a41f053260da986cd0252b156f3866520)

rust-timer · 2024-10-26T12:14:13Z

Finished benchmarking commit (bbf9ed8): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	5.1%	[0.3%, 16.8%]	75
Regressions ❌ (secondary)	4.8%	[0.1%, 29.4%]	30
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	5.1%	[0.3%, 16.8%]	75

Max RSS (memory usage)

Results (primary 4.2%, secondary 3.1%)

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)	4.2%	[1.0%, 10.1%]	68
Regressions ❌ (secondary)	3.4%	[0.9%, 6.1%]	25
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.0%	[-3.0%, -3.0%]	1
All ❌✅ (primary)	4.2%	[1.0%, 10.1%]	68

Cycles

Results (primary 11.1%, secondary 12.1%)

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)	11.1%	[1.2%, 26.2%]	56
Regressions ❌ (secondary)	17.3%	[2.9%, 38.6%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.6%	[-4.9%, -2.9%]	3
All ❌✅ (primary)	11.1%	[1.2%, 26.2%]	56

Binary size

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

Bootstrap: 785.03s -> 787.479s (0.31%)
Artifact size: 333.74 MiB -> 333.57 MiB (-0.05%)

veluca93 · 2024-10-26T14:18:26Z

@jieyouxu / @RalfJung could I get another perf run?

jieyouxu · 2024-10-26T14:28:47Z

You'll probably need to fix the compilation error to make it buildable, but yes

compiler-errors · 2024-10-26T16:27:15Z

The call-site check is more tricky since the inputs currently are (callee_ty, *fn_span, self.body.source.instance).

@RalfJung: Why not just make the query something like (callee_ty, instance) which then returns some "status" or something that captures "should we emit a lint?" that you then use at the call-site to turn into a lint, rather than making the query responsible for emitting the lint? I agree that you almost never want to pass a span to a query.

veluca93 · 2024-10-26T16:54:34Z

The call-site check is more tricky since the inputs currently are (callee_ty, *fn_span, self.body.source.instance).

@RalfJung: Why not just make the query something like (callee_ty, instance) which then returns some "status" or something that captures "should we emit a lint?" that you then use at the call-site to turn into a lint, rather than making the query responsible for emitting the lint? I agree that you almost never want to pass a span to a query.

I thought of doing the same too - I also gave up on the previous attempt since that got in a somewhat annoying rabbit hole.
Should be ready for a perf run now!

saethlin · 2024-10-26T20:03:48Z

@bors try @rust-timer queue

Emit warning when calling/declaring functions with unavailable vectors. On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.) As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code. This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI. See the [nomination comment](rust-lang#127731 (comment)) for more discussion. Part of rust-lang#116558 r? RalfJung

bors · 2024-10-26T20:05:00Z

⌛ Trying commit 75c873a with merge 95e2c91...

bors · 2024-10-26T21:56:16Z

☀️ Try build successful - checks-actions
Build commit: 95e2c91 (95e2c91a1f2db67bbad2800a9838d921ab01cbbb)

rust-timer · 2024-10-27T00:16:15Z

Finished benchmarking commit (95e2c91): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	1.7%	[0.2%, 3.8%]	48
Regressions ❌ (secondary)	1.9%	[1.0%, 2.7%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.7%	[0.2%, 3.8%]	48

Max RSS (memory usage)

Results (primary 3.1%, secondary -0.8%)

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)	3.4%	[1.4%, 6.5%]	21
Regressions ❌ (secondary)	4.4%	[4.4%, 4.4%]	1
Improvements ✅ (primary)	-1.8%	[-1.8%, -1.8%]	1
Improvements ✅ (secondary)	-1.6%	[-4.0%, -0.4%]	6
All ❌✅ (primary)	3.1%	[-1.8%, 6.5%]	22

Cycles

Results (primary 3.2%, secondary 3.0%)

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)	3.2%	[1.6%, 6.3%]	29
Regressions ❌ (secondary)	3.0%	[3.0%, 3.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.2%	[1.6%, 6.3%]	29

Binary size

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

Bootstrap: 783.187s -> 786.602s (0.44%)
Artifact size: 333.73 MiB -> 333.78 MiB (0.02%)

jieyouxu · 2024-10-31T09:44:03Z

@bors try @rust-timer queue

bors · 2024-10-31T09:45:13Z

⌛ Trying commit bb070b7 with merge a84f27efcc5ecacb4eb2fc8c301ecafb33780102...

Emit warning when calling/declaring functions with unavailable vectors. On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.) As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code. This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI. See the [nomination comment](rust-lang#127731 (comment)) for more discussion. Part of rust-lang#116558 r? RalfJung

bors · 2024-10-31T11:37:20Z

☀️ Try build successful - checks-actions
Build commit: a84f27e (a84f27efcc5ecacb4eb2fc8c301ecafb33780102)

rust-timer · 2024-10-31T13:40:15Z

Finished benchmarking commit (a84f27e): comparison URL.

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

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	0.9%	[0.2%, 1.9%]	47
Regressions ❌ (secondary)	1.2%	[0.8%, 1.4%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	0.9%	[0.2%, 1.9%]	47

Max RSS (memory usage)

Results (primary 1.4%, secondary 0.8%)

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)	1.9%	[0.7%, 3.4%]	10
Regressions ❌ (secondary)	3.6%	[1.5%, 5.8%]	2
Improvements ✅ (primary)	-1.2%	[-1.3%, -1.0%]	2
Improvements ✅ (secondary)	-4.9%	[-4.9%, -4.9%]	1
All ❌✅ (primary)	1.4%	[-1.3%, 3.4%]	12

Cycles

Results (primary 2.6%, secondary 2.7%)

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)	2.6%	[1.2%, 4.5%]	22
Regressions ❌ (secondary)	2.7%	[2.5%, 2.8%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.6%	[1.2%, 4.5%]	22

Binary size

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

Bootstrap: 783.635s -> 785.568s (0.25%)
Artifact size: 333.60 MiB -> 333.70 MiB (0.03%)

compiler/rustc_monomorphize/src/collector.rs

compiler/rustc_monomorphize/src/collector/abi_check.rs

RalfJung · 2024-10-31T16:56:48Z

compiler/rustc_monomorphize/src/collector/abi_check.rs

+    // Note that the check is still correct on Rust ABI functions, but somewhat expensive. Hence,
+    // checking for "Rust" ABI is just an optimization.
+    // We also avoid to try to determine the type of the instance, as doing so involves running a
+    // query that does not usually run for unchanged functions in incremental builds.


Is that query cached on disk or are we actually doing computational work here?

AFAIU it is actually computed.

The type_of query is cache_on_disk_if { key.is_local() }... but also separate_provide_extern... no idea what that means for its performance characteristics. @cjgillot can you think of any way to speed this up further?

Actually the relevant query is fn_sig.

compiler/rustc_monomorphize/src/collector/abi_check.rs

On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.) As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code. This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI. See the [nomination comment](rust-lang#127731 (comment)) for more discussion. Part of rust-lang#116558

RalfJung · 2024-10-31T20:05:20Z

compiler/rustc_monomorphize/src/collector/abi_check.rs

+    // query that does not usually run for unchanged functions in incremental builds.
+    match instance.def {
+        // We only need to check for user-defined functions - if all user-defined functions are
+        // fine, so are the `instance`s derived by the compiler.


More importantly, the instances always use Rust ABI, as far as I know. (But someone should confirm this.)

RalfJung · 2024-10-31T20:05:37Z

@bors try
@rust-timer queue

Emit warning when calling/declaring functions with unavailable vectors. On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.) As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code. This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI. See the [nomination comment](rust-lang#127731 (comment)) for more discussion. Part of rust-lang#116558 r? RalfJung

bors · 2024-10-31T20:06:48Z

⌛ Trying commit f6bba9a with merge e529a2f...

bors · 2024-10-31T21:59:24Z

☀️ Try build successful - checks-actions
Build commit: e529a2f (e529a2f4709150e129ec9db1e519dff4ec2388bb)

rust-timer · 2024-11-01T00:20:25Z

Finished benchmarking commit (e529a2f): comparison URL.

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

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	0.8%	[0.2%, 1.7%]	47
Regressions ❌ (secondary)	1.1%	[0.7%, 1.4%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.0%	[-1.9%, -0.2%]	2
All ❌✅ (primary)	0.8%	[0.2%, 1.7%]	47

Max RSS (memory usage)

Results (primary 1.7%, secondary -0.3%)

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)	1.7%	[0.7%, 3.7%]	7
Regressions ❌ (secondary)	2.5%	[2.0%, 3.3%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.4%	[-2.1%, -0.7%]	7
All ❌✅ (primary)	1.7%	[0.7%, 3.7%]	7

Cycles

Results (primary 2.5%, secondary 1.0%)

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)	2.5%	[1.3%, 3.3%]	21
Regressions ❌ (secondary)	2.3%	[2.1%, 2.5%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.2%	[-3.2%, -3.2%]	1
All ❌✅ (primary)	2.5%	[1.3%, 3.3%]	21

Binary size

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

Bootstrap: 782.659s -> 785.576s (0.37%)
Artifact size: 333.43 MiB -> 333.69 MiB (0.08%)

RalfJung · 2024-11-01T06:30:46Z

There is one more idea I have... which is to have a query that takes an Instance, and then checks that entire instance for ABI issues, i.e. both the instance itself as a caller as well as all the call sites inside of it. If we cache that instance, that would then be only one extra query per instance in incremental builds. It does require that query to do its own MIR walk, but walking all terminators of a MIR body should be fairly quick.

rustbot assigned RalfJung Oct 26, 2024

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 Oct 26, 2024

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veluca93 force-pushed the abi_checks branch from 4526613 to cc25da0 Compare October 26, 2024 14:18

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Mark-Simulacrum mentioned this pull request Oct 26, 2024

ABI compatibility: remove section on target features #132136

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Emit warning when calling/declaring functions with unavailable vectors. #132173

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Emit warning when calling/declaring functions with unavailable vectors. #132173

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veluca93 commented Oct 26, 2024

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rust-timer commented Oct 26, 2024

Overall result: ❌ regressions - please read the text below

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compiler-errors commented Oct 26, 2024 • edited Loading

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rust-timer commented Oct 27, 2024

Overall result: ❌ regressions - please read the text below

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

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rust-timer commented Nov 1, 2024

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

RalfJung commented Nov 1, 2024

compiler-errors commented Oct 26, 2024 •

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