Remove unused pred_pos

src/cfg.rs

@@ -26,15 +26,6 @@ pub struct CFGInfo {
     pub block_entry: Vec<ProgPoint>,
     /// For each block, the last instruction.
     pub block_exit: Vec<ProgPoint>,
-    /// For each block, what is its position in its successor's preds,
-    /// if it has a single successor?
-    ///
-    /// (Because we require split critical edges, we always either have a single
-    /// successor (which itself may have multiple preds), or we have multiple
-    /// successors but each successor itself has only one pred; so we can store
-    /// just one value per block and always know any block's position in its
-    /// successors' preds lists.)
-    pub pred_pos: Vec<usize>,
     /// For each block, what is the approximate loop depth?
     ///
     /// This measure is fully precise iff the input CFG is reducible
@@ -60,7 +51,6 @@ impl CFGInfo {
         let mut vreg_def_blockparam = vec![(Block::invalid(), 0); f.num_vregs()];
         let mut block_entry = vec![ProgPoint::before(Inst::invalid()); f.blocks()];
         let mut block_exit = vec![ProgPoint::before(Inst::invalid()); f.blocks()];
-        let mut pred_pos = vec![0; f.blocks()];
         let mut backedge_in = vec![0; f.blocks()];
         let mut backedge_out = vec![0; f.blocks()];
 
@@ -88,12 +78,11 @@ impl CFGInfo {
             // (this block).
             let preds = f.block_preds(block).len() + if block == f.entry_block() { 1 } else { 0 };
             if preds > 1 {
-                for (i, &pred) in f.block_preds(block).iter().enumerate() {
+                for &pred in f.block_preds(block) {
                     let succs = f.block_succs(pred).len();
                     if succs > 1 {
                         return Err(RegAllocError::CritEdge(pred, block));
                     }
-                    pred_pos[pred.index()] = i;
                 }
             }
 
@@ -153,7 +142,6 @@ impl CFGInfo {
             vreg_def_blockparam,
             block_entry,
             block_exit,
-            pred_pos,
             approx_loop_depth,
         })
     }
@@ -161,14 +149,4 @@ impl CFGInfo {
     pub fn dominates(&self, a: Block, b: Block) -> bool {
         domtree::dominates(&self.domtree[..], a, b)
     }
-
-    /// Return the position of this block in its successor's predecessor list.
-    ///
-    /// Because the CFG must have split critical edges, we actually do not need
-    /// to know *which* successor: if there is more than one, then each
-    /// successor has only one predecessor (that's this block), so the answer is
-    /// `0` no matter which successor we are considering.
-    pub fn pred_position(&self, block: Block) -> usize {
-        self.pred_pos[block.index()]
-    }
 }