From 32251b6229c30143b2ab2b66dbed38aa386c9b9e Mon Sep 17 00:00:00 2001
From: Trevor Elliott <telliott@fastly.com>
Date: Mon, 29 Aug 2022 16:57:19 -0700
Subject: [PATCH] Move the nop lowering to ISLE, and remove the final return
 from lower.rs

---
 cranelift/codegen/src/isa/x64/lower.isle | 6 ++++++
 cranelift/codegen/src/isa/x64/lower.rs   | 9 ++-------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/cranelift/codegen/src/isa/x64/lower.isle b/cranelift/codegen/src/isa/x64/lower.isle
index 1c413f148a13..f3dafda6cc89 100644
--- a/cranelift/codegen/src/isa/x64/lower.isle
+++ b/cranelift/codegen/src/isa/x64/lower.isle
@@ -3757,3 +3757,9 @@
 
         ;; SHUFPS xmm_y, xmm_xmp, 0x88
         (x64_shufps dst zeros 0x88)))
+
+;; Rules for `nop` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(rule (lower (nop))
+      (invalid_reg))
+
diff --git a/cranelift/codegen/src/isa/x64/lower.rs b/cranelift/codegen/src/isa/x64/lower.rs
index 6d1a0bec61bb..88ef7e500ce5 100644
--- a/cranelift/codegen/src/isa/x64/lower.rs
+++ b/cranelift/codegen/src/isa/x64/lower.rs
@@ -459,7 +459,8 @@ fn lower_insn_to_regs(
         | Opcode::Isplit
         | Opcode::TlsValue
         | Opcode::SqmulRoundSat
-        | Opcode::Uunarrow => {
+        | Opcode::Uunarrow
+        | Opcode::Nop => {
             let ty = if outputs.len() > 0 {
                 Some(ctx.output_ty(insn, 0))
             } else {
@@ -572,13 +573,7 @@ fn lower_insn_to_regs(
         | Opcode::BrTable => {
             panic!("Branch opcode reached non-branch lowering logic!");
         }
-
-        Opcode::Nop => {
-            // Nothing.
-        }
     }
-
-    Ok(())
 }
 
 //=============================================================================