pan/midgard: Add mir_foreach_successor helper

Now we should be able to walk the control-flow graph naturally.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

src/panfrost/midgard/compiler.h

@@ -360,6 +360,14 @@ mir_next_op(struct midgard_instruction *ins)
         mir_foreach_block(ctx, v_block) \
                 mir_foreach_instr_in_block_safe(v_block, v)
 
+#define mir_foreach_successor(blk, v) \
+        struct midgard_block *v; \
+        struct midgard_block **_v; \
+        for (_v = &blk->successors[0], \
+                v = *_v; \
+                v != NULL && _v < &blk->successors[2]; \
+                _v++, v = *_v) \
+
 /* Based on set_foreach, expanded with automatic type casts */
 
 #define mir_foreach_predecessor(blk, v) \