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| author | Mark Rousskov <mark.simulacrum@gmail.com> | 2025-06-22 17:51:56 -0400 |
|---|---|---|
| committer | Mark Rousskov <mark.simulacrum@gmail.com> | 2025-06-22 17:52:49 -0400 |
| commit | 928564c7bfb395e1e5bd34d8913b7627ee4d1130 (patch) | |
| tree | c34b6152a04edcf5303a142c7a226576e0ee79fa | |
| parent | d4e1159b8c97478778b09a4cc1c7adce5653b8bf (diff) | |
| download | rust-928564c7bfb395e1e5bd34d8913b7627ee4d1130.tar.gz rust-928564c7bfb395e1e5bd34d8913b7627ee4d1130.zip | |
Stop collecting unmentioned constants
This avoids generating useless dead LLVM IR.
| -rw-r--r-- | compiler/rustc_monomorphize/src/collector.rs | 14 | ||||
| -rw-r--r-- | tests/codegen-units/partitioning/vtable-through-const.rs | 5 |
2 files changed, 8 insertions, 11 deletions
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs index 173030e0326..3eb9a9dc850 100644 --- a/compiler/rustc_monomorphize/src/collector.rs +++ b/compiler/rustc_monomorphize/src/collector.rs @@ -1481,12 +1481,14 @@ impl<'v> RootCollector<'_, 'v> { // Const items only generate mono items if they are actually used somewhere. // Just declaring them is insufficient. - // But even just declaring them must collect the items they refer to - // unless their generics require monomorphization. - if !self.tcx.generics_of(id.owner_id).own_requires_monomorphization() - && let Ok(val) = self.tcx.const_eval_poly(id.owner_id.to_def_id()) - { - collect_const_value(self.tcx, val, self.output); + // If we're collecting items eagerly, then recurse into all constants. + // Otherwise the value is only collected when explicitly mentioned in other items. + if self.strategy == MonoItemCollectionStrategy::Eager { + if !self.tcx.generics_of(id.owner_id).own_requires_monomorphization() + && let Ok(val) = self.tcx.const_eval_poly(id.owner_id.to_def_id()) + { + collect_const_value(self.tcx, val, self.output); + } } } DefKind::Impl { .. } => { diff --git a/tests/codegen-units/partitioning/vtable-through-const.rs b/tests/codegen-units/partitioning/vtable-through-const.rs index aad9ccb634b..7a070728843 100644 --- a/tests/codegen-units/partitioning/vtable-through-const.rs +++ b/tests/codegen-units/partitioning/vtable-through-const.rs @@ -35,7 +35,6 @@ mod mod1 { } } - //~ MONO_ITEM fn mod1::id::<i64> @@ vtable_through_const-mod1.volatile[Internal] fn id<T>(x: T) -> T { x } @@ -50,8 +49,6 @@ mod mod1 { fn do_something_else(&self) {} } - //~ MONO_ITEM fn <mod1::NeedsDrop as mod1::Trait2>::do_something @@ vtable_through_const-mod1.volatile[External] - //~ MONO_ITEM fn <mod1::NeedsDrop as mod1::Trait2>::do_something_else @@ vtable_through_const-mod1.volatile[External] impl Trait2 for NeedsDrop {} pub trait Trait2Gen<T> { @@ -93,8 +90,6 @@ pub fn main() { // Same as above //~ MONO_ITEM fn <mod1::NeedsDrop as mod1::Trait1Gen<u8>>::do_something @@ vtable_through_const-mod1.volatile[External] //~ MONO_ITEM fn <mod1::NeedsDrop as mod1::Trait1Gen<u8>>::do_something_else @@ vtable_through_const-mod1.volatile[External] - //~ MONO_ITEM fn <mod1::NeedsDrop as mod1::Trait2Gen<u8>>::do_something @@ vtable_through_const-mod1.volatile[External] - //~ MONO_ITEM fn <mod1::NeedsDrop as mod1::Trait2Gen<u8>>::do_something_else @@ vtable_through_const-mod1.volatile[External] mod1::TRAIT1_GEN_REF.do_something(0u8); //~ MONO_ITEM fn mod1::id::<char> @@ vtable_through_const-mod1.volatile[External] |