Stop generating `alloca`s+`memcmp` for simple array equality

1 files changed, 18 insertions, 0 deletions

diff --git a/compiler/rustc_mir/src/interpret/intrinsics.rs b/compiler/rustc_mir/src/interpret/intrinsics.rs
index 4e4166dad50..5dd679b8912 100644
--- a/compiler/rustc_mir/src/interpret/intrinsics.rs
+++ b/compiler/rustc_mir/src/interpret/intrinsics.rs
@@ -472,6 +472,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     throw_ub_format!("`assume` intrinsic called with `false`");
                 }
             }
+            sym::raw_eq => {
+                let result = self.raw_eq_intrinsic(&args[0], &args[1])?;
+                self.write_scalar(result, dest)?;
+            }
             _ => return Ok(false),
         }
 
@@ -559,4 +563,18 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         self.memory.copy(src, align, dst, align, size, nonoverlapping)
     }
+
+    pub(crate) fn raw_eq_intrinsic(
+        &mut self,
+        lhs: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::PointerTag>,
+        rhs: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::PointerTag>,
+    ) -> InterpResult<'tcx, Scalar<M::PointerTag>> {
+        let layout = self.layout_of(lhs.layout.ty.builtin_deref(true).unwrap().ty)?;
+
+        let lhs = self.read_scalar(lhs)?.check_init()?;
+        let rhs = self.read_scalar(rhs)?.check_init()?;
+        let lhs_bytes = self.memory.read_bytes(lhs, layout.size)?;
+        let rhs_bytes = self.memory.read_bytes(rhs, layout.size)?;
+        Ok(Scalar::Int((lhs_bytes == rhs_bytes).into()))
+    }
 }