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the wasm ABI behavior is a bug

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This commit is contained in:
Ralf Jung 2023-09-07 16:04:22 +02:00
parent 243ef313a5
commit 28d152935e
3 changed files with 15 additions and 11 deletions
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15
compiler/rustc_codegen_llvm/src/abi.rs
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@ -351,15 +351,12 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
// guarnateeing that we generate ABI-compatible LLVM IR. Things get tricky for
// aggregates...
if matches!(arg.layout.abi, abi::Abi::Aggregate { .. }) {
// This is the most critical case for ABI compatibility, since
// `immediate_llvm_type` will use `layout.fields` to turn this Rust type
// into an LLVM type. ABI-compatible Rust types can have different `fields`,
// so we need to be very sure that LLVM wil treat those different types in
// an ABI-compatible way. Mostly we do this by disallowing
// `PassMode::Direct` for aggregates, but we actually do use that mode on
// wasm. wasm doesn't have aggregate types so we are fairly sure that LLVM
// will treat `{ i32, i32, i32 }` and `{ { i32, i32, i32 } }` the same way
// for ABI purposes.
// This really shouldn't happen, since `immediate_llvm_type` will use
// `layout.fields` to turn this Rust type into an LLVM type. This means all
// sorts of Rust type details leak into the ABI. However wasm sadly *does*
// currently use this mode so we have to allow it -- but we absolutely
// shouldn't let any more targets do that.
// (Also see <https://github.com/rust-lang/rust/issues/115666>.)
assert!(
matches!(&*cx.tcx.sess.target.arch, "wasm32" | "wasm64"),
"`PassMode::Direct` for aggregates only allowed on wasm targets\nProblematic type: {:#?}",