aco: consider blocks unreachable if they are in the logical cfg

unreachable was true if the last block is unreachable in the linear cfg,
but it should also be true if it is unreachable in the logical cfg.

Fixes dEQP-VK.graphicsfuzz.for-with-ifs-and-return

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Fixes: 8d8c864beb
    ('aco: improve check for unreachable loop continue blocks')

Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4764>

src/amd/compiler/aco_instruction_selection.cpp

@@ -9552,8 +9552,6 @@ static bool visit_if(isel_context *ctx, nir_if *if_stmt)
       visit_cf_list(ctx, &if_stmt->else_list);
 
       end_uniform_if(ctx, &ic);
-
-      return !ctx->cf_info.has_branch;
    } else { /* non-uniform condition */
       /**
        * To maintain a logical and linear CFG without critical edges,
@@ -9587,9 +9585,9 @@ static bool visit_if(isel_context *ctx, nir_if *if_stmt)
       visit_cf_list(ctx, &if_stmt->else_list);
 
       end_divergent_if(ctx, &ic);
-
-      return true;
    }
+
+   return !ctx->cf_info.has_branch && !ctx->block->logical_preds.empty();
 }
 
 static bool visit_cf_list(isel_context *ctx,