Implement inline(usually)

Author: saethlin

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -9,6 +9,7 @@ use crate::RustcVersion;
 pub enum InlineAttr {
     None,
     Hint,
+    Usually,
     Always,
     Never,
     /// `#[rustc_force_inline]` forces inlining to happen in the MIR inliner - it reports an error
@@ -24,7 +25,7 @@ impl InlineAttr {
     pub fn always(&self) -> bool {
         match self {
             InlineAttr::Always | InlineAttr::Force { .. } => true,
-            InlineAttr::None | InlineAttr::Hint | InlineAttr::Never => false,
+            InlineAttr::None | InlineAttr::Hint | InlineAttr::Usually | InlineAttr::Never => false,
         }
     }
 }

compiler/rustc_codegen_gcc/src/attributes.rs

@@ -19,7 +19,7 @@ fn inline_attr<'gcc, 'tcx>(
     inline: InlineAttr,
 ) -> Option<FnAttribute<'gcc>> {
     match inline {
-        InlineAttr::Hint => Some(FnAttribute::Inline),
+        InlineAttr::Hint | InlineAttr::Usually => Some(FnAttribute::Inline),
         InlineAttr::Always | InlineAttr::Force { .. } => Some(FnAttribute::AlwaysInline),
         InlineAttr::Never => {
             if cx.sess().target.arch != "amdgpu" {

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -40,6 +40,9 @@ fn inline_attr<'ll>(cx: &CodegenCx<'ll, '_>, inline: InlineAttr) -> Option<&'ll
         InlineAttr::Always | InlineAttr::Force { .. } => {
             Some(AttributeKind::AlwaysInline.create_attr(cx.llcx))
         }
+        InlineAttr::Usually => {
+            Some(llvm::CreateAttrStringValue(cx.llcx, "function-inline-cost", "0"))
+        }
         InlineAttr::Never => {
             if cx.sess().target.arch != "amdgpu" {
                 Some(AttributeKind::NoInline.create_attr(cx.llcx))

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -551,6 +551,8 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                 InlineAttr::None
             } else if list_contains_name(items, sym::always) {
                 InlineAttr::Always
+            } else if list_contains_name(items, sym::usually) {
+                InlineAttr::Usually
             } else if list_contains_name(items, sym::never) {
                 InlineAttr::Never
             } else {

compiler/rustc_mir_transform/src/cross_crate_inline.rs

@@ -46,7 +46,9 @@ fn cross_crate_inlinable(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
     // #[inline(never)] to force code generation.
     match codegen_fn_attrs.inline {
         InlineAttr::Never => return false,
-        InlineAttr::Hint | InlineAttr::Always | InlineAttr::Force { .. } => return true,
+        InlineAttr::Hint | InlineAttr::Usually | InlineAttr::Always | InlineAttr::Force { .. } => {
+            return true;
+        }
         _ => {}
     }
 

compiler/rustc_mir_transform/src/inline.rs

@@ -299,7 +299,10 @@ impl<'tcx> Inliner<'tcx> for NormalInliner<'tcx> {
             changed: false,
             caller_is_inline_forwarder: matches!(
                 codegen_fn_attrs.inline,
-                InlineAttr::Hint | InlineAttr::Always | InlineAttr::Force { .. }
+                InlineAttr::Hint
+                    | InlineAttr::Usually
+                    | InlineAttr::Always
+                    | InlineAttr::Force { .. }
             ) && body_is_forwarder(body),
         }
     }

compiler/rustc_span/src/symbol.rs

@@ -2178,6 +2178,7 @@ symbols! {
         usize_legacy_fn_max_value,
         usize_legacy_fn_min_value,
         usize_legacy_mod,
+        usually,
         v8plus,
         va_arg,
         va_copy,