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.

Author: bors

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -35,13 +35,25 @@ pub enum InstructionSetAttr {
     ArmT32,
 }
 
-#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
+#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic, Default)]
 pub enum OptimizeAttr {
-    None,
+    /// No `#[optimize(..)]` attribute
+    #[default]
+    Default,
+    /// `#[optimize(none)]`
+    DoNotOptimize,
+    /// `#[optimize(speed)]`
     Speed,
+    /// `#[optimize(size)]`
     Size,
 }
 
+impl OptimizeAttr {
+    pub fn do_not_optimize(&self) -> bool {
+        matches!(self, Self::DoNotOptimize)
+    }
+}
+
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub enum DiagnosticAttribute {
     // tidy-alphabetical-start

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -333,22 +333,25 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
     let mut to_add = SmallVec::<[_; 16]>::new();
 
     match codegen_fn_attrs.optimize {
-        OptimizeAttr::None => {
+        OptimizeAttr::Default => {
             to_add.extend(default_optimisation_attrs(cx));
         }
+        OptimizeAttr::DoNotOptimize => {
+            to_add.push(llvm::AttributeKind::OptimizeNone.create_attr(cx.llcx));
+        }
         OptimizeAttr::Size => {
             to_add.push(llvm::AttributeKind::MinSize.create_attr(cx.llcx));
             to_add.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
         }
         OptimizeAttr::Speed => {}
     }
 
-    let inline =
-        if codegen_fn_attrs.inline == InlineAttr::None && instance.def.requires_inline(cx.tcx) {
-            InlineAttr::Hint
-        } else {
-            codegen_fn_attrs.inline
-        };
+    // `optnone` requires `noinline`
+    let inline = match (codegen_fn_attrs.inline, &codegen_fn_attrs.optimize) {
+        (_, OptimizeAttr::DoNotOptimize) => InlineAttr::Never,
+        (InlineAttr::None, _) if instance.def.requires_inline(cx.tcx) => InlineAttr::Hint,
+        (inline, _) => inline,
+    };
     to_add.extend(inline_attr(cx, inline));
 
     // The `uwtable` attribute according to LLVM is:

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 {

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
         }
     });
 

compiler/rustc_feature/src/builtin_attrs.rs

@@ -532,7 +532,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ),
     // RFC 2412
     gated!(
-        optimize, Normal, template!(List: "size|speed"), ErrorPreceding,
+        optimize, Normal, template!(List: "none|size|speed"), ErrorPreceding,
         EncodeCrossCrate::No, optimize_attribute, experimental!(optimize)
     ),
 

compiler/rustc_middle/src/middle/codegen_fn_attrs.rs

@@ -147,7 +147,7 @@ impl CodegenFnAttrs {
         CodegenFnAttrs {
             flags: CodegenFnAttrFlags::empty(),
             inline: InlineAttr::None,
-            optimize: OptimizeAttr::None,
+            optimize: OptimizeAttr::Default,
             export_name: None,
             link_name: None,
             link_ordinal: None,

compiler/rustc_mir_transform/src/abort_unwinding_calls.rs

@@ -116,4 +116,8 @@ impl<'tcx> crate::MirPass<'tcx> for AbortUnwindingCalls {
         // We may have invalidated some `cleanup` blocks so clean those up now.
         super::simplify::remove_dead_blocks(body);
     }
+
+    fn is_required(&self) -> bool {
+        true
+    }
 }

compiler/rustc_mir_transform/src/add_call_guards.rs

@@ -75,4 +75,8 @@ impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
 
         body.basic_blocks_mut().extend(new_blocks);
     }
+
+    fn is_required(&self) -> bool {
+        true
+    }
 }

compiler/rustc_mir_transform/src/add_moves_for_packed_drops.rs

@@ -68,6 +68,10 @@ impl<'tcx> crate::MirPass<'tcx> for AddMovesForPackedDrops {
 
         patch.apply(body);
     }
+
+    fn is_required(&self) -> bool {
+        true
+    }
 }
 
 fn add_move_for_packed_drop<'tcx>(

compiler/rustc_mir_transform/src/add_retag.rs

@@ -176,4 +176,8 @@ impl<'tcx> crate::MirPass<'tcx> for AddRetag {
             }
         }
     }
+
+    fn is_required(&self) -> bool {
+        true
+    }
 }