Pass arguments up to 2*usize by value #79547
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| pub union UnionU128x2{a:(u128, u128)} | ||
| // CHECK: define void @test_UnionU128x2(i128 %_1.0, i128 %_1.1) | ||
| #[no_mangle] | ||
| pub fn test_UnionU128x2(_: UnionU128x2) { loop {} } | ||
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| #[repr(C)] | ||
| pub union CUnionU128{a:u128} | ||
| // CHECK: define void @test_CUnionU128(%CUnionU128* {{.*}} %_1) | ||
| pub union CUnionU128x2{a:(u128, u128)} | ||
| // CHECK: define void @test_CUnionU128x2(%CUnionU128x2* {{.*}} %_1) | ||
| #[no_mangle] | ||
| pub fn test_CUnionU128(_: CUnionU128) { loop {} } | ||
| pub fn test_CUnionU128x2(_: CUnionU128x2) { loop {} } |
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This was testing that single-field #[repr(C)] unions don't forward that field's ABI, but after this change CUnionU128 would get passed by value, making it impossible to distinguish between i128 [forwarded from inner field] vs i128 [passing entire union by value]. So I had to make it bigger.
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@bors try @rust-timer queue |
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Awaiting bors try build completion |
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⌛ Trying commit 0183b41 with merge 6b84c5f481a691b1da945054fe9c6311fca322dd... |
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☀️ Try build successful - checks-actions |
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Queued 6b84c5f481a691b1da945054fe9c6311fca322dd with parent 349b3b3, future comparison URL. |
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Finished benchmarking try commit (6b84c5f481a691b1da945054fe9c6311fca322dd): comparison url. Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. Please note that if the perf results are neutral, you should likely undo the rollup=never given below by specifying Importantly, though, if the results of this run are non-neutral do not roll this PR up -- it will mask other regressions or improvements in the roll up. @bors rollup=never |
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@bors r+ |
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📌 Commit 53943d6 has been approved by |
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☀️ Test successful - checks-actions |
In #77434 (comment), @eddyb said:
Let's do a perf run and find out.
It seems the
extern "C"ABI will pass arguments up to 2*usize in registers: https://godbolt.org/z/n8E6zc. (modified from #26494 (comment))r? @nagisa