diff options
Diffstat (limited to 'compiler/rustc_codegen_llvm')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/abi.rs | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs index 863cb7068f8..64587f98b8a 100644 --- a/compiler/rustc_codegen_llvm/src/abi.rs +++ b/compiler/rustc_codegen_llvm/src/abi.rs @@ -340,15 +340,50 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> { }; for arg in args { + // Note that the exact number of arguments pushed here is carefully synchronized with + // code all over the place, both in the codegen_llvm and codegen_ssa crates. That's how + // other code then knows which LLVM argument(s) correspond to the n-th Rust argument. let llarg_ty = match &arg.mode { PassMode::Ignore => continue, - PassMode::Direct(_) => arg.layout.immediate_llvm_type(cx), + PassMode::Direct(_) => { + // ABI-compatible Rust types have the same `layout.abi` (up to validity ranges), + // and for Scalar ABIs the LLVM type is fully determined by `layout.abi`, + // guarnateeing that we generate ABI-compatible LLVM IR. Things get tricky for + // aggregates... + if matches!(arg.layout.abi, abi::Abi::Aggregate { .. }) { + // 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: {:#?}", + arg.layout, + ); + } + arg.layout.immediate_llvm_type(cx) + } PassMode::Pair(..) => { + // ABI-compatible Rust types have the same `layout.abi` (up to validity ranges), + // so for ScalarPair we can easily be sure that we are generating ABI-compatible + // LLVM IR. + assert!( + matches!(arg.layout.abi, abi::Abi::ScalarPair(..)), + "PassMode::Pair for type {}", + arg.layout.ty + ); llargument_tys.push(arg.layout.scalar_pair_element_llvm_type(cx, 0, true)); llargument_tys.push(arg.layout.scalar_pair_element_llvm_type(cx, 1, true)); continue; } PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => { + assert!(arg.layout.is_unsized()); + // Construct the type of a (wide) pointer to `ty`, and pass its two fields. + // Any two ABI-compatible unsized types have the same metadata type and + // moreover the same metadata value leads to the same dynamic size and + // alignment, so this respects ABI compatibility. let ptr_ty = Ty::new_mut_ptr(cx.tcx, arg.layout.ty); let ptr_layout = cx.layout_of(ptr_ty); llargument_tys.push(ptr_layout.scalar_pair_element_llvm_type(cx, 0, true)); @@ -360,6 +395,8 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> { if *pad_i32 { llargument_tys.push(Reg::i32().llvm_type(cx)); } + // Compute the LLVM type we use for this function from the cast type. + // We assume here that ABI-compatible Rust types have the same cast type. cast.llvm_type(cx) } PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => cx.type_ptr(), |