Auto merge of #143182 - xdoardo:more-addrspace, r=workingjubilee

Allow custom default address spaces and parse `p-` specifications in the datalayout string

Some targets, such as CHERI, use as default an address space different from the "normal" default address space `0` (in the case of CHERI, [200 is used](https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-877.pdf)). Currently, `rustc` does not allow to specify custom address spaces and does not take into consideration [`p-` specifications in the datalayout string](https://llvm.org/docs/LangRef.html#langref-datalayout).

This patch tries to mitigate these problems by allowing targets to define a custom default address space (while keeping the default value to address space `0`) and adding the code to parse the `p-` specifications in `rustc_abi`. The main changes are that `TargetDataLayout` now uses functions to refer to pointer-related informations, instead of having specific fields for the size and alignment of pointers in the default address space; furthermore, the two `pointer_size` and `pointer_align` fields in `TargetDataLayout` are replaced with an `FxHashMap` that holds info for all the possible address spaces, as parsed by the `p-` specifications.

The potential performance drawbacks of not having ad-hoc fields for the default address space will be tested in this PR's CI run.

r? workingjubilee

1 files changed, 2 insertions, 2 deletions

diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index a225b712d4b..163e2b30883 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -379,7 +379,7 @@ fn layout_of_uncached<'tcx>(
 
         // Potentially-wide pointers.
         ty::Ref(_, pointee, _) | ty::RawPtr(pointee, _) => {
-            let mut data_ptr = scalar_unit(Pointer(AddressSpace::DATA));
+            let mut data_ptr = scalar_unit(Pointer(AddressSpace::ZERO));
             if !ty.is_raw_ptr() {
                 data_ptr.valid_range_mut().start = 1;
             }
@@ -435,7 +435,7 @@ fn layout_of_uncached<'tcx>(
                     }
                     ty::Slice(_) | ty::Str => scalar_unit(Int(dl.ptr_sized_integer(), false)),
                     ty::Dynamic(..) => {
-                        let mut vtable = scalar_unit(Pointer(AddressSpace::DATA));
+                        let mut vtable = scalar_unit(Pointer(AddressSpace::ZERO));
                         vtable.valid_range_mut().start = 1;
                         vtable
                     }