From ec2a9993595ac8e12058355d1b8c06fb6a5a8e99 Mon Sep 17 00:00:00 2001
From: Chris Fallin <chris@cfallin.org>
Date: Sun, 12 Feb 2023 13:53:03 -0800
Subject: [PATCH] Add block names to irreducible-control-flow error

---
 src/backend/stackify.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/backend/stackify.rs b/src/backend/stackify.rs
index aec02ea..67ca6a2 100644
--- a/src/backend/stackify.rs
+++ b/src/backend/stackify.rs
@@ -129,7 +129,13 @@ impl<'a, 'b> Context<'a, 'b> {
                 log::trace!(" -> succ rpo {}", succ_rpo);
                 if succ_rpo <= block_rpo {
                     if !cfg.dominates(succ, block) {
-                        anyhow::bail!("Irreducible control flow: edge from {} to {}", block, succ);
+                        anyhow::bail!(
+                            "Irreducible control flow: edge from {} ({}) to {} ({})",
+                            block,
+                            body.blocks[block].desc,
+                            succ,
+                            body.blocks[succ].desc
+                        );
                     }
                     // Backward branch.
                     loop_headers.insert(succ);