Fix simd_gather

Author: antoyo

src/builder.rs

@@ -1923,18 +1923,35 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             self.int_type
         };
 
-        let vector_type =
-            mask.get_type().dyncast_vector().expect("simd_shuffle mask should be of vector type");
-        let mask_num_units = vector_type.get_num_units();
-        let mut mask_elements = vec![];
-        for i in 0..mask_num_units {
-            let index = self.context.new_rvalue_from_long(self.cx.type_u32(), i as _);
-            mask_elements.push(self.context.new_cast(
-                self.location,
-                self.extract_element(mask, index).to_rvalue(),
-                mask_element_type,
-            ));
-        }
+        // NOTE: this condition is needed because we call shuffle_vector in the implementation of
+        // simd_gather.
+        let mut mask_elements = if let Some(vector_type) = mask.get_type().dyncast_vector() {
+            let mask_num_units = vector_type.get_num_units();
+            let mut mask_elements = vec![];
+            for i in 0..mask_num_units {
+                let index = self.context.new_rvalue_from_long(self.cx.type_u32(), i as _);
+                mask_elements.push(self.context.new_cast(
+                    self.location,
+                    self.extract_element(mask, index).to_rvalue(),
+                    mask_element_type,
+                ));
+            }
+            mask_elements
+        } else {
+            let struct_type = mask.get_type().is_struct().expect("mask should be of struct type");
+            let mask_num_units = struct_type.get_field_count();
+            let mut mask_elements = vec![];
+            for i in 0..mask_num_units {
+                let field = struct_type.get_field(i as i32);
+                mask_elements.push(self.context.new_cast(
+                    self.location,
+                    mask.access_field(self.location, field).to_rvalue(),
+                    mask_element_type,
+                ));
+            }
+            mask_elements
+        };
+        let mask_num_units = mask_elements.len();
 
         // NOTE: the mask needs to be the same length as the input vectors, so add the missing
         // elements in the mask if needed.