From 26da67b39461c8f88f27819c158ef80820fe3519 Mon Sep 17 00:00:00 2001
From: Dan Gohman <sunfish@mozilla.com>
Date: Tue, 6 Nov 2018 10:38:29 -0800
Subject: [PATCH] Add a verifier check that ghost instructions don't have
 encodings.

---
 lib/codegen/src/verifier/mod.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lib/codegen/src/verifier/mod.rs b/lib/codegen/src/verifier/mod.rs
index 6fedcc5af2..31a7dfc029 100644
--- a/lib/codegen/src/verifier/mod.rs
+++ b/lib/codegen/src/verifier/mod.rs
@@ -1550,6 +1550,15 @@ impl<'a> Verifier<'a> {
 
         let encoding = self.func.encodings[inst];
         if encoding.is_legal() {
+            if self.func.dfg[inst].opcode().is_ghost() {
+                return nonfatal!(
+                    errors,
+                    inst,
+                    "Ghost instruction has an encoding: {}",
+                    isa.encoding_info().display(encoding)
+                );
+            }
+
             let mut encodings = isa
                 .legal_encodings(
                     &self.func,