From 92d9bff69495e74d42a640ddd2a12ea1540857bc Mon Sep 17 00:00:00 2001
From: Steven Allen <steven@stebalien.com>
Date: Tue, 28 Jun 2022 20:03:16 -0700
Subject: [PATCH] Wasmtime: disable unwind_info unless needed

fixes #4350

Otherwise wasm modules will be built with unwind info, even if
backtraces are disabled. This can get expensive in deeply recursive
modules.
---
 crates/wasmtime/src/config.rs | 2 ++
 crates/wasmtime/src/engine.rs | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/crates/wasmtime/src/config.rs b/crates/wasmtime/src/config.rs
index b41ae9396f43..d2c905ea4872 100644
--- a/crates/wasmtime/src/config.rs
+++ b/crates/wasmtime/src/config.rs
@@ -1423,6 +1423,8 @@ impl Config {
             {
                 bail!("compiler option 'unwind_info' must be enabled when either 'backtraces' or 'reference types' are enabled");
             }
+        } else {
+            self.compiler_config.settings.insert("unwind_info", "false");
         }
         if self.features.reference_types {
             if !self
diff --git a/crates/wasmtime/src/engine.rs b/crates/wasmtime/src/engine.rs
index 9dd637e7143f..b86e636da535 100644
--- a/crates/wasmtime/src/engine.rs
+++ b/crates/wasmtime/src/engine.rs
@@ -345,7 +345,6 @@ impl Engine {
             // can affect the way the generated code performs or behaves at
             // runtime.
             "avoid_div_traps" => *value == FlagValue::Bool(true),
-            "unwind_info" => *value == FlagValue::Bool(true),
             "libcall_call_conv" => *value == FlagValue::Enum("isa_default".into()),
 
             // Features wasmtime doesn't use should all be disabled, since
@@ -381,6 +380,7 @@ impl Engine {
             | "enable_verifier"
             | "regalloc_checker"
             | "is_pic"
+            | "unwind_info"
             | "machine_code_cfg_info"
             | "tls_model" // wasmtime doesn't use tls right now
             | "opt_level" // opt level doesn't change semantics