Auto merge of #76260 - xd009642:rfc/2867, r=jonas-schievink

Implementation of RFC2867

https://github.com/rust-lang/rust/issues/74727

So I've started work on this, I think my next steps are to make use of the `instruction_set` value in the llvm codegen but this is the point where I begin to get a bit lost. I'm looking at the code but it would be nice to have some guidance on what I've currently done and what I'm doing next :smile:

1 files changed, 5 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index a633ea5e5a9..f02c30c3ee3 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -18,7 +18,7 @@ use crate::attributes;
 use crate::llvm::AttributePlace::Function;
 use crate::llvm::{self, Attribute};
 use crate::llvm_util;
-pub use rustc_attr::{InlineAttr, OptimizeAttr};
+pub use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 
 use crate::context::CodegenCx;
 use crate::value::Value;
@@ -310,6 +310,10 @@ pub fn from_fn_attrs(cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value, instance: ty::
             let feature = &f.as_str();
             format!("+{}", llvm_util::to_llvm_feature(cx.tcx.sess, feature))
         }))
+        .chain(codegen_fn_attrs.instruction_set.iter().map(|x| match x {
+            InstructionSetAttr::ArmA32 => "-thumb-mode".to_string(),
+            InstructionSetAttr::ArmT32 => "+thumb-mode".to_string(),
+        }))
         .collect::<Vec<String>>()
         .join(",");