Add llvm.type.checked.load intrinsic

Add the intrinsic

declare {i8*, i1} @llvm.type.checked.load(i8* %ptr, i32 %offset, metadata %type)

This is used in the VFE optimization when lowering loading functions
from vtables to LLVM IR. The `metadata` is used to map the function to
all vtables this function could belong to. This ensures that functions
from vtables that might be used somewhere won't get removed.

2 files changed, 15 insertions, 3 deletions

diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 27fe60161d5..b5c31fcebe0 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -665,6 +665,7 @@ impl<'ll> CodegenCx<'ll, '_> {
         let t_isize = self.type_isize();
         let t_f32 = self.type_f32();
         let t_f64 = self.type_f64();
+        let t_metadata = self.type_metadata();
 
         ifn!("llvm.wasm.trunc.unsigned.i32.f32", fn(t_f32) -> t_i32);
         ifn!("llvm.wasm.trunc.unsigned.i32.f64", fn(t_f64) -> t_i32);
@@ -890,11 +891,12 @@ impl<'ll> CodegenCx<'ll, '_> {
             ifn!("llvm.instrprof.increment", fn(i8p, t_i64, t_i32, t_i32) -> void);
         }
 
-        ifn!("llvm.type.test", fn(i8p, self.type_metadata()) -> i1);
+        ifn!("llvm.type.test", fn(i8p, t_metadata) -> i1);
+        ifn!("llvm.type.checked.load", fn(i8p, t_i32, t_metadata) -> mk_struct! {i8p, i1});
 
         if self.sess().opts.debuginfo != DebugInfo::None {
-            ifn!("llvm.dbg.declare", fn(self.type_metadata(), self.type_metadata()) -> void);
-            ifn!("llvm.dbg.value", fn(self.type_metadata(), t_i64, self.type_metadata()) -> void);
+            ifn!("llvm.dbg.declare", fn(t_metadata, t_metadata) -> void);
+            ifn!("llvm.dbg.value", fn(t_metadata, t_i64, t_metadata) -> void);
         }
         None
     }
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 9927f5f399b..a18f5b9dd7f 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -406,6 +406,16 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         self.call_intrinsic("llvm.type.test", &[bitcast, typeid])
     }
 
+    fn type_checked_load(
+        &mut self,
+        llvtable: &'ll Value,
+        vtable_byte_offset: u64,
+        typeid: &'ll Value,
+    ) -> Self::Value {
+        let vtable_byte_offset = self.const_i32(vtable_byte_offset as i32);
+        self.call_intrinsic("llvm.type.checked.load", &[llvtable, vtable_byte_offset, typeid])
+    }
+
     fn va_start(&mut self, va_list: &'ll Value) -> &'ll Value {
         self.call_intrinsic("llvm.va_start", &[va_list])
     }