Add scalar support for offload by Sa4dUs · Pull Request #150288 · rust-lang/rust

Sa4dUs · 2025-12-22T20:20:23Z

This PR adds scalar support to the offload feature. The scalar management has two main parts:

On the host side, each scalar arg is casted to ix type, zero extended to i64 and passed to the kernel like that.
On the device, the each scalar arg (i64 at that point), is truncated to ix and then casted to the original type.

r? @ZuseZ4

ZuseZ4 · 2025-12-30T13:46:56Z

@Sa4dUs, what's the current state of this? Given the omp/ol expectation of scalars being 64 bit integers I guess this code only works for i64 and usize and everything else will need the casts (or only works by chance)?
I'm fine with having casts in a follow-up PR, but I guess we should start having more test files in which we check that all the different argument types are being handled correctly, so at least an i64 test for this one?

Sa4dUs · 2025-12-30T19:45:15Z

it works for all 64-bit scalars. for f64 it's not what omp expects but somehow it just works, not sure it it will break in some weird edge case

rust-bors · 2026-01-02T23:05:14Z

☔ The latest upstream changes made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2026-01-03T00:03:49Z

☔ The latest upstream changes (presumably #150606) made this pull request unmergeable. Please resolve the merge conflicts.

rustbot · 2026-01-14T17:56:28Z

r? @jdonszelmann

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ZuseZ4 · 2026-01-19T20:21:14Z

+ let mut old_args_rebuilt = Vec::with_capacity(old_param_types.len());
+
+ for (i, &old_ty) in old_param_types.iter().enumerate() {
+ let new_arg = unsafe { llvm::LLVMGetParam(new_fn, (i + 1) as u32) };


I had missed this one. Otherwise lgtm.
Use compiler/rustc_codegen_llvm/src/llvm/mod.rs
287 /// Safe wrapper around `LLVMGetParam`, because segfaults are no fun. 1 pub(crate) fn get_param(llfn: &Value, index: c_uint) -> &Value {

ZuseZ4 · 2026-01-19T20:29:57Z

+// CHECK: store double 4.200000e+01, ptr %0, align 8
+// CHECK: %_0.i = load double, ptr %0, align 8
+// CHECK: store double %_0.i, ptr %addr, align 8
+// CHECK-NEXT: call void @__tgt_register_lib(ptr nonnull %EmptyDesc)


While at it, can you please remove the check for : call void @__tgt_register_lib(ptr nonnull %EmptyDesc)? My other open PR moves it into globals, so that would break this test.

ZuseZ4 · 2026-01-19T20:53:02Z

+ let ty_kind = cx.type_kind(ty);
+ let (base_val, gep_base) = match ty_kind {
+ TypeKind::Pointer => (v, v),
+ TypeKind::Half | TypeKind::Float | TypeKind::Double | TypeKind::Integer => {


Add a FIXME that we should later check for f128 support. At least newer NVIDIA cards should support it.

ZuseZ4 · 2026-01-19T21:08:33Z

+
+// CHECK: define{{( dso_local)?}} void @main()
+// CHECK-NOT: define
+// CHECK: %EmptyDesc = alloca %struct.__tgt_bin_desc, align 8


Oh and also remove this

ZuseZ4 · 2026-01-19T21:44:01Z

@bors delegate
r=me when CI passes.

rust-bors · 2026-01-19T21:44:04Z

✌️ @Sa4dUs, you can now approve this pull request!

If @ZuseZ4 told you to "r=me" after making some further change, then please make that change and post @bors r=ZuseZ4.

Sa4dUs · 2026-01-19T23:08:40Z

@bors r=ZuseZ4

rust-bors · 2026-01-19T23:08:43Z

📌 Commit 307a4fc has been approved by ZuseZ4

It is now in the queue for this repository.

@ZuseZ4

Add scalar support for offload This PR adds scalar support to the offload feature. The scalar management has two main parts: On the host side, each scalar arg is casted to `ix` type, zero extended to `i64` and passed to the kernel like that. On the device, the each scalar arg (`i64` at that point), is truncated to `ix` and then casted to the original type. r? @ZuseZ4

@ghost

Rollup of 8 pull requests Successful merges: - #149587 (coverage: Sort the expansion tree to help choose a single BCB for child expansions) - #150071 (Add dist step for Enzyme) - #150288 (Add scalar support for offload) - #151091 (Add new "hide deprecated items" setting in rustdoc) - #151255 (rustdoc: Fix ICE when deprecated note is not resolved on the correct `DefId`) - #151375 (Fix terminal width dependent tests) - #151384 (add basic `TokenStream` api tests) - #151391 (rustc-dev-guide subtree update) r? @ghost

@ZuseZ4

Rollup merge of #150288 - offload-bench-fix, r=ZuseZ4 Add scalar support for offload This PR adds scalar support to the offload feature. The scalar management has two main parts: On the host side, each scalar arg is casted to `ix` type, zero extended to `i64` and passed to the kernel like that. On the device, the each scalar arg (`i64` at that point), is truncated to `ix` and then casted to the original type. r? @ZuseZ4

@ghost

Rollup of 8 pull requests Successful merges: - rust-lang/rust#149587 (coverage: Sort the expansion tree to help choose a single BCB for child expansions) - rust-lang/rust#150071 (Add dist step for Enzyme) - rust-lang/rust#150288 (Add scalar support for offload) - rust-lang/rust#151091 (Add new "hide deprecated items" setting in rustdoc) - rust-lang/rust#151255 (rustdoc: Fix ICE when deprecated note is not resolved on the correct `DefId`) - rust-lang/rust#151375 (Fix terminal width dependent tests) - rust-lang/rust#151384 (add basic `TokenStream` api tests) - rust-lang/rust#151391 (rustc-dev-guide subtree update) r? @ghost

Sa4dUs force-pushed the offload-bench-fix branch from d99cf66 to 0330a0eCompare December 26, 2025 16:49

ZuseZ4 reviewed Dec 31, 2025
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Comment threadcompiler/rustc_codegen_llvm/src/builder/gpu_offload.rs Outdated
Comment threadcompiler/rustc_codegen_llvm/src/builder/gpu_offload.rs

Sa4dUs force-pushed the offload-bench-fix branch from 0330a0e to ea71b7bCompare January 3, 2026 17:03

ZuseZ4 mentioned this pull request Jan 6, 2026
Tracking Issue for GPU-offload #131513
Open
5 tasks

Sa4dUs force-pushed the offload-bench-fix branch from ea71b7b to 8b7e6b6Compare January 7, 2026 13:28

Sa4dUs added 2 commits January 14, 2026 11:37

Minor doc and ty fixes
bc751ad

Allow bounded types
2c9c5d1

Sa4dUs force-pushed the offload-bench-fix branch 2 times, most recently from 5189bbb to 45ccec5Compare January 14, 2026 15:30

Sa4dUs changed the title ~~WIP Offload Benchmarks Fixes~~Add scalar support for offloadJan 14, 2026

Sa4dUs force-pushed the offload-bench-fix branch from 45ccec5 to 38f7fc7Compare January 14, 2026 15:38

Sa4dUs marked this pull request as ready for review January 14, 2026 17:56

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 14, 2026

rustbot assigned jdonszelmann Jan 14, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jan 14, 2026

rustbot assigned ZuseZ4 and unassigned jdonszelmann Jan 14, 2026

ZuseZ4 reviewed Jan 14, 2026
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Sa4dUs force-pushed the offload-bench-fix branch from 38f7fc7 to 5e980e1Compare January 14, 2026 19:42

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Sa4dUs force-pushed the offload-bench-fix branch from 5e980e1 to 272a1a6Compare January 15, 2026 00:06

ZuseZ4 mentioned this pull request Jan 16, 2026
Finish the std::offload module rust-lang/goals#109
Closed
8 tasks

ZuseZ4 reviewed Jan 19, 2026
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Add scalar support for both host and device
307a4fc

Sa4dUs force-pushed the offload-bench-fix branch from 272a1a6 to 307a4fcCompare January 19, 2026 21:31

rust-borsBot 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 Jan 19, 2026

This was referenced Jan 20, 2026
Rollup of 9 pull requests #151392
Closed
Rollup of 8 pull requests #151395
Merged

rust-borsBot merged commit 1262ff9 into rust-lang:mainJan 20, 2026
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rustbot added this to the 1.95.0 milestone Jan 20, 2026

ZuseZ4 added the F-gpu_offload `#![feature(gpu_offload)]` label Apr 28, 2026

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Sa4dUs commented Dec 22, 2025•
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