Auto merge of #128657 - clubby789:optimize-none, r=fee1-dead,WaffleLapkin

Add `#[optimize(none)]`

cc #54882

This extends the `optimize` attribute to add `none`, which corresponds to the LLVM `OptimizeNone` attribute.

Not sure if an MCP is required for this, happy to file one if so.

2 files changed, 7 insertions, 8 deletions

diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 83724af604d..6099dec2bb2 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -1053,10 +1053,7 @@ pub(crate) fn provide(providers: &mut Providers) {
 
         let any_for_speed = defids.items().any(|id| {
             let CodegenFnAttrs { optimize, .. } = tcx.codegen_fn_attrs(*id);
-            match optimize {
-                attr::OptimizeAttr::None | attr::OptimizeAttr::Size => false,
-                attr::OptimizeAttr::Speed => true,
-            }
+            matches!(optimize, attr::OptimizeAttr::Speed)
         });
 
         if any_for_speed {
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 1daa17fbaf3..a0bc2d4ea48 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -575,7 +575,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         codegen_fn_attrs.inline = InlineAttr::Never;
     }
 
-    codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
+    codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::Default, |ia, attr| {
         if !attr.has_name(sym::optimize) {
             return ia;
         }
@@ -587,17 +587,19 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             inline_span = Some(attr.span);
             if items.len() != 1 {
                 err(attr.span, "expected one argument");
-                OptimizeAttr::None
+                OptimizeAttr::Default
             } else if list_contains_name(items, sym::size) {
                 OptimizeAttr::Size
             } else if list_contains_name(items, sym::speed) {
                 OptimizeAttr::Speed
+            } else if list_contains_name(items, sym::none) {
+                OptimizeAttr::DoNotOptimize
             } else {
                 err(items[0].span(), "invalid argument");
-                OptimizeAttr::None
+                OptimizeAttr::Default
             }
         } else {
-            OptimizeAttr::None
+            OptimizeAttr::Default
         }
     });