Re: [PATCH] RISC-V: Refactor the function bitmap_union_of_preds_with_entry

[Robin Dapp]

Hi Ma Jin,

thanks for looking into this, it has been on my todo list with very low 
priority since the vsetvl rewrite.

+  /* Handle case with no predecessors (including ENTRY block).  */
+  if (EDGE_COUNT (b->preds) == 0)
     {
-      e = EDGE_PRED (b, ix);
-      bitmap_copy (dst, src[e->src->index]);
-      break;
+      bitmap_clear (dst);
+      return;

This is ok.

+  /* Initialize with first predecessor's bitmap.  */
+  edge first_pred = EDGE_PRED (b, 0);
+  bitmap_copy (dst, src[first_pred->src->index]);
+
+  /* Union remaining predecessors' bitmaps.  */
+  for (unsigned ix = 1; ix < EDGE_COUNT (b->preds); ix++)
+    {
+      edge e = EDGE_PRED (b, ix);
+      const sbitmap pred_src = src[e->src->index];
+
+      /* Perform bitmap OR operation element-wise.  */
+      for (unsigned i = 0; i < dst->size; i++)
+       dst->elms[i] |= pred_src->elms[i];
+    }

To my taste this could be simplified further like

 FOR_EACH_EDGE (e, ei, b->preds)
   {
     if (ei.index == 0)
        {
          bitmap_copy (dst, src[e->src->index]);
          continue;
        }

     bitmap_ior (dst, dst, src[e->src->index]);
   }

Does that work as well?

--
Regards
Robin