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_middle/src/ty/vtable.rs b/compiler/rustc_middle/src/ty/vtable.rs
index 74b6a840a2e..6fc19c82342 100644
--- a/compiler/rustc_middle/src/ty/vtable.rs
+++ b/compiler/rustc_middle/src/ty/vtable.rs
@@ -106,8 +106,8 @@ pub(super) fn vtable_allocation_provider<'tcx>(
     let size = layout.size.bytes();
     let align = layout.align.abi.bytes();
 
-    let ptr_size = tcx.data_layout.pointer_size;
-    let ptr_align = tcx.data_layout.pointer_align.abi;
+    let ptr_size = tcx.data_layout.pointer_size();
+    let ptr_align = tcx.data_layout.pointer_align().abi;
 
     let vtable_size = ptr_size * u64::try_from(vtable_entries.len()).unwrap();
     let mut vtable = Allocation::new(vtable_size, ptr_align, AllocInit::Uninit, ());