From 095a883814638ed0b0ef0c492da015ad164e54e6 Mon Sep 17 00:00:00 2001
From: Chris Fallin <chris@cfallin.org>
Date: Sun, 9 May 2021 01:06:59 -0700
Subject: [PATCH] Fix crit-edge detection logic in CFGInfo analysis

---
 src/cfg.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/cfg.rs b/src/cfg.rs
index f73ca1a..cf4428c 100644
--- a/src/cfg.rs
+++ b/src/cfg.rs
@@ -72,10 +72,12 @@ impl CFGInfo {
             block_entry[block.index()] = ProgPoint::before(f.block_insns(block).first());
             block_exit[block.index()] = ProgPoint::after(f.block_insns(block).last());
 
-            if f.block_preds(block).len() > 1 {
+            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() {
                     // Check critical edge condition.
-                    if f.block_succs(pred).len() > 1 {
+                    let succs = f.block_succs(pred).len();
+                    if succs > 1 {
                         return Err(RegAllocError::CritEdge(pred, block));
                     }
                     pred_pos[pred.index()] = i;