codegen_ssa: multiply scalable vec size by `vscale` by davidtwco · Pull Request #158253 · rust-lang/rust

davidtwco · 2026-06-22T14:43:20Z

Part of rust-lang/stdarch#2160. When emitting a memcpy for a scalable vector, the size computed by rustc (num_vectors * element_count * element_ty), since #157915, needs to be multiplied by vscale.

rustbot · 2026-06-22T14:43:26Z

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When emitting a `memcpy` for a scalable vector, the size computed by rustc (`num_vectors * element_count * element_ty`), since rust-lang#157915, needs to be multiplied by `vscale`.

rustbot · 2026-06-22T15:06:55Z

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

cc @antoyo, @GuillaumeGomez

rustbot · 2026-06-22T15:06:58Z

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rust-bors · 2026-06-24T12:28:41Z

📌 Commit cfc4211 has been approved by mati865

It is now in the queue for this repository.

…scale, r=mati865 codegen_ssa: multiply scalable vec size by `vscale` Part of rust-lang/stdarch#2160. When emitting a `memcpy` for a scalable vector, the size computed by rustc (`num_vectors * element_count * element_ty`), since rust-lang#157915, needs to be multiplied by `vscale`.

…uwer Rollup of 17 pull requests Successful merges: - #153697 (Add arg splat experiment initial tuple impl) - #158294 (Use .drectve for MSVC DLL exports) - #158253 (codegen_ssa: multiply scalable vec size by `vscale`) - #158308 (Fix bug when rustdoc "go to only result" setting is not working as expected") - #158345 (Use `transmute_neo` in `assume_init`) - #158369 (std: abort when `resume_unwind` is called inside the panic hook) - #158374 (disallow tail calling extern "rust-call" functions) - #158380 (Revert "rebuild LLVM when `bootstrap.toml` config changes") - #154398 (Add test for async Send with PhantomData<*mut ()> + unsafe impl Send + dyn Trait) - #157181 (autodiff: stop always needing an alloca) - #158278 (autodiff - typtree cleanups) - #158311 (doc(unstable-book): fix typo "earier" -> "earlier" in default-visibility flag) - #158318 (Make normalization in a test case resilient to dist compilation) - #158338 (Reorganize `tests/ui/issues` [14/N]) - #158343 (Include `Item::const_stability` info in rustdoc JSON.) - #158355 (Fixup the refactoring errors in #156246) - #158390 (Fix: auto trait, const trait bound) Failed merges: - #155535 (export symbols: support macos/windows(32/64))

…scale, r=mati865 codegen_ssa: multiply scalable vec size by `vscale` Part of rust-lang/stdarch#2160. When emitting a `memcpy` for a scalable vector, the size computed by rustc (`num_vectors * element_count * element_ty`), since rust-lang#157915, needs to be multiplied by `vscale`.

…uwer Rollup of 17 pull requests Successful merges: - #153697 (Add arg splat experiment initial tuple impl) - #155535 (export symbols: support macos/windows(32/64)) - #158253 (codegen_ssa: multiply scalable vec size by `vscale`) - #158308 (Fix bug when rustdoc "go to only result" setting is not working as expected") - #158345 (Use `transmute_neo` in `assume_init`) - #158369 (std: abort when `resume_unwind` is called inside the panic hook) - #158374 (disallow tail calling extern "rust-call" functions) - #158380 (Revert "rebuild LLVM when `bootstrap.toml` config changes") - #154398 (Add test for async Send with PhantomData<*mut ()> + unsafe impl Send + dyn Trait) - #157181 (autodiff: stop always needing an alloca) - #158278 (autodiff - typtree cleanups) - #158311 (doc(unstable-book): fix typo "earier" -> "earlier" in default-visibility flag) - #158318 (Make normalization in a test case resilient to dist compilation) - #158338 (Reorganize `tests/ui/issues` [14/N]) - #158343 (Include `Item::const_stability` info in rustdoc JSON.) - #158355 (Fixup the refactoring errors in #156246) - #158390 (Fix: auto trait, const trait bound)

scottmcm · 2026-06-25T16:47:24Z

            let bytes = self.const_usize(layout.size.bytes());
+            let bytes = if layout.peel_transparent_wrappers(self).ty.is_scalable_vector() {
+                let vscale = self.vscale(self.type_i64());
+                self.mul(vscale, bytes)


pondering: should this be unchecked_sumul?

Also, it's really not good if everywhere looking at sizes needs to look at vscale specifically. How can it be moved into layout better?

View changes since the review

I expect we'll end up refactoring Layout in some way that makes it easier to ensure that users think about the scalable case, and that when they do, it's easy to get right. For now, this patch is sufficient to get stdarch testing which is useful to keep things working.

…scale, r=mati865 codegen_ssa: multiply scalable vec size by `vscale` Part of rust-lang/stdarch#2160. When emitting a `memcpy` for a scalable vector, the size computed by rustc (`num_vectors * element_count * element_ty`), since rust-lang#157915, needs to be multiplied by `vscale`.

…uwer Rollup of 16 pull requests Successful merges: - #153697 (Add arg splat experiment initial tuple impl) - #155535 (export symbols: support macos/windows(32/64)) - #158253 (codegen_ssa: multiply scalable vec size by `vscale`) - #158308 (Fix bug when rustdoc "go to only result" setting is not working as expected") - #158345 (Use `transmute_neo` in `assume_init`) - #158369 (std: abort when `resume_unwind` is called inside the panic hook) - #158374 (disallow tail calling extern "rust-call" functions) - #158380 (Revert "rebuild LLVM when `bootstrap.toml` config changes") - #154398 (Add test for async Send with PhantomData<*mut ()> + unsafe impl Send + dyn Trait) - #157181 (autodiff: stop always needing an alloca) - #158278 (autodiff - typtree cleanups) - #158311 (doc(unstable-book): fix typo "earier" -> "earlier" in default-visibility flag) - #158318 (Make normalization in a test case resilient to dist compilation) - #158338 (Reorganize `tests/ui/issues` [14/N]) - #158343 (Include `Item::const_stability` info in rustdoc JSON.) - #158390 (Fix: auto trait, const trait bound) Failed merges: - #158355 (Fixup the refactoring errors in #156246)

…uwer Rollup of 15 pull requests Successful merges: - #155535 (export symbols: support macos/windows(32/64)) - #158253 (codegen_ssa: multiply scalable vec size by `vscale`) - #158308 (Fix bug when rustdoc "go to only result" setting is not working as expected") - #158345 (Use `transmute_neo` in `assume_init`) - #158369 (std: abort when `resume_unwind` is called inside the panic hook) - #158374 (disallow tail calling extern "rust-call" functions) - #158380 (Revert "rebuild LLVM when `bootstrap.toml` config changes") - #154398 (Add test for async Send with PhantomData<*mut ()> + unsafe impl Send + dyn Trait) - #157181 (autodiff: stop always needing an alloca) - #158278 (autodiff - typtree cleanups) - #158311 (doc(unstable-book): fix typo "earier" -> "earlier" in default-visibility flag) - #158318 (Make normalization in a test case resilient to dist compilation) - #158338 (Reorganize `tests/ui/issues` [14/N]) - #158343 (Include `Item::const_stability` info in rustdoc JSON.) - #158390 (Fix: auto trait, const trait bound)

Rollup merge of #158253 - davidtwco:scalable-vector-memcpy-vscale, r=mati865 codegen_ssa: multiply scalable vec size by `vscale` Part of rust-lang/stdarch#2160. When emitting a `memcpy` for a scalable vector, the size computed by rustc (`num_vectors * element_count * element_ty`), since #157915, needs to be multiplied by `vscale`.

rustbot assigned mati865 Jun 22, 2026

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intrinsic-test: sve support rust-lang/stdarch#2160

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Tracking Issue for Scalable Vectors #145052

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codegen_ssa: multiply scalable vec size by vscale

cfc4211

When emitting a `memcpy` for a scalable vector, the size computed by rustc (`num_vectors * element_count * element_ty`), since rust-lang#157915, needs to be multiplied by `vscale`.

davidtwco force-pushed the scalable-vector-memcpy-vscale branch from 90c76ec to cfc4211 Compare June 22, 2026 15:06

mati865 reviewed Jun 24, 2026

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Comment thread compiler/rustc_codegen_ssa/src/traits/builder.rs

mati865 approved these changes Jun 24, 2026

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rust-bors Bot 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 Jun 24, 2026

JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 18 pull requests #158386

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JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 17 pull requests #158389

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JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 17 pull requests #158391

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JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 17 pull requests #158395

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scottmcm reviewed Jun 25, 2026

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JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 16 pull requests #158413

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JonathanBrouwer mentioned this pull request Jun 25, 2026

Rollup of 15 pull requests #158416

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rust-bors Bot merged commit e20298b into rust-lang:main Jun 25, 2026
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codegen_ssa: multiply scalable vec size by `vscale`#158253

codegen_ssa: multiply scalable vec size by `vscale`#158253
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