From 43125aa994438b2692e2407d410d3b6b81c2cbd5 Mon Sep 17 00:00:00 2001
From: Peter Huene <phuene@fastly.com>
Date: Tue, 2 Aug 2022 13:28:43 -0700
Subject: [PATCH] components: fix trampoline compilation for lists. (#4579)

This commit fixes trampoline compilation for lists where the loop condition
would only branch if the amount remaining was 0 instead of not 0.

It resulted in only the first element of the list being copied.
---
 crates/environ/src/fact/trampoline.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/crates/environ/src/fact/trampoline.rs b/crates/environ/src/fact/trampoline.rs
index 405e8489c0..1ad9c2c9a7 100644
--- a/crates/environ/src/fact/trampoline.rs
+++ b/crates/environ/src/fact/trampoline.rs
@@ -833,6 +833,7 @@ impl Compiler<'_, '_> {
             let src_add = if src_opts.memory64 { I64Add } else { I32Add };
             let dst_add = if dst_opts.memory64 { I64Add } else { I32Add };
             let src_eqz = if src_opts.memory64 { I64Eqz } else { I32Eqz };
+            let src_ne = if src_opts.memory64 { I64Ne } else { I32Ne };
 
             // This block encompasses the entire loop and is use to exit before even
             // entering the loop if the list size is zero.
@@ -887,7 +888,8 @@ impl Compiler<'_, '_> {
             self.instruction(iconst(-1, src_opts.ptr()));
             self.instruction(src_add.clone());
             self.instruction(LocalTee(remaining));
-            self.instruction(src_eqz.clone());
+            self.instruction(iconst(0, src_opts.ptr()));
+            self.instruction(src_ne.clone());
             self.instruction(BrIf(0));
             self.instruction(End); // end of loop
             self.instruction(End); // end of block