fix ice nested array

Author: tesuji

compiler/rustc_mir_transform/src/promote_consts_local_arrays.rs

@@ -252,6 +252,7 @@ impl<'a, 'tcx> std::ops::Deref for Validator<'a, 'tcx> {
 struct Unpromotable;
 
 impl<'tcx> Validator<'_, 'tcx> {
+    #[instrument(level = "trace", skip(self))]
     fn validate_candidate(&mut self, candidate: Location) -> Result<(), Unpromotable> {
         let Left(statement) = self.body.stmt_at(candidate) else { bug!() };
         let Some((place, rvalue @ Rvalue::Aggregate(box kind, operands))) =
@@ -276,6 +277,8 @@ impl<'tcx> Validator<'_, 'tcx> {
             && size.bytes() <= STACK_THRESHOLD
         {
             debug!("size of array is too small: {:?}", size);
+            // for nested arrays
+            self.temps[place.local] = TempState::Unpromotable;
             return Err(Unpromotable);
         }
 

tests/mir-opt/const_array_locals.rs

@@ -34,6 +34,9 @@ pub fn main() {
         159, 22, 157, 105, 31, 96, 173, 50, 1,]);
 
     let _f = F32x8([1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0]);
+
+    // ice
+    [[1, 0, 0], [0, 1, 0], [0, 0, 1]]; // 2D array
 }
 
 fn consume(_arr: [u16; 32]) {