Code review feedback.

* Removed `Config::cranelift_clear_cpu_flags`.
* Renamed `Config::cranelift_other_flag` to `Config::cranelift::flag_set`.
* Renamed `--cranelift-flag` to `--cranelift-set`.
* Renamed `--cranelift-preset` to `--cranelift-enable`.

RELEASES.md

@@ -11,8 +11,14 @@
 
 * The `Module::compile` method was added to support AOT compilation of a module.
 
-* Added the `Config::cranelift_flag_enable` to enable setting Cranelift boolean
-  flags or presets in a config.
+* Added the `Config::target` method to change the compilation target of the
+  configuration. This can be used in conjunction with `Module::compile` to target
+  a different host triple than the current one.
+
+* Added the `Config::cranelift_flag_enable` method to enable setting Cranelift
+  boolean flags or presets in a config.
+
+* Added CLI option `--cranelift-enable` to enable boolean settings and ISA presets.
 
 ### Changed
 
@@ -20,7 +26,12 @@
   singular `--wasm-features` option. The previous options are still supported, but
   are not displayed in help text.
 
-* Breaking: the CLI option `--cranelift-flags` was changed to `--cranelift-flag`.
+* Breaking: `Config::cranelift_clear_cpu_flags` was removed. Use `Config::target`
+  to clear the CPU flags for the host's target.
+
+* Breaking: `Config::cranelift_other_flag` was renamed to `Config::cranelift_flag_set`.
+
+* Breaking: the CLI option `--cranelift-flags` was changed to `--cranelift-set`.
 
 * Breaking: the CLI option `--enable-reference-types=false` has been changed to
   `--wasm-features=-reference-types`.

crates/wasmtime/src/config.rs

@@ -441,10 +441,8 @@ impl Config {
     ///
     /// This method can be used to change the target triple.
     ///
-    /// Note that any no Cranelift flags will be inferred for the given target.
-    ///
-    /// [`Config::cranelift_clear_cpu_flags`] will reset the target triple back to
-    /// the host's target.
+    /// Cranelift flags will not be inferred for the given target and any
+    /// existing target-specific Cranelift flags will be cleared.
     ///
     /// # Errors
     ///
@@ -898,22 +896,6 @@ impl Config {
         self
     }
 
-    /// Clears native CPU flags inferred from the host.
-    ///
-    /// Note: this method will change the target to that of the host.
-    ///
-    /// By default Wasmtime will tune generated code for the host that Wasmtime
-    /// itself is running on. If you're compiling on one host, however, and
-    /// shipping artifacts to another host then this behavior may not be
-    /// desired. This function will clear all inferred native CPU features.
-    ///
-    /// To enable CPU features afterwards it's recommended to use the
-    /// [`Config::cranelift_other_flag`] method.
-    pub fn cranelift_clear_cpu_flags(&mut self) -> &mut Self {
-        self.isa_flags = native::builder_without_flags();
-        self
-    }
-
     /// Allows setting a Cranelift boolean flag or preset. This allows
     /// fine-tuning of Cranelift settings.
     ///
@@ -954,7 +936,7 @@ impl Config {
     ///
     /// This method can fail if the flag's name does not exist, or the value is not appropriate for
     /// the flag type.
-    pub unsafe fn cranelift_other_flag(&mut self, name: &str, value: &str) -> Result<&mut Self> {
+    pub unsafe fn cranelift_flag_set(&mut self, name: &str, value: &str) -> Result<&mut Self> {
         if let Err(err) = self.flags.set(name, value) {
             match err {
                 SetError::BadName(_) => {

src/lib.rs

@@ -213,12 +213,12 @@ struct CommonOptions {
     opt_level: Option<wasmtime::OptLevel>,
 
     /// Cranelift common flags to set.
-    #[structopt(long = "cranelift-flag", value_name = "NAME=VALUE", parse(try_from_str = parse_cranelift_flag))]
-    cranelift_flags: Vec<CraneliftFlag>,
+    #[structopt(long = "cranelift-set", value_name = "NAME=VALUE", parse(try_from_str = parse_cranelift_flag))]
+    cranelift_set: Vec<(String, String)>,
 
-    /// The Cranelift ISA preset to use.
-    #[structopt(long, value_name = "PRESET")]
-    cranelift_preset: Option<String>,
+    /// The Cranelift boolean setting or preset to enable.
+    #[structopt(long, value_name = "SETTING")]
+    cranelift_enable: Vec<String>,
 
     /// Maximum size in bytes of wasm memory before it becomes dynamically
     /// relocatable instead of up-front-reserved.
@@ -273,15 +273,15 @@ impl CommonOptions {
 
         self.enable_wasm_features(&mut config);
 
-        if let Some(preset) = &self.cranelift_preset {
+        for name in &self.cranelift_enable {
             unsafe {
-                config.cranelift_flag_enable(preset)?;
+                config.cranelift_flag_enable(name)?;
             }
         }
 
-        for CraneliftFlag { name, value } in &self.cranelift_flags {
+        for (name, value) in &self.cranelift_set {
             unsafe {
-                config.cranelift_other_flag(name, value)?;
+                config.cranelift_flag_set(name, value)?;
             }
         }
 
@@ -401,13 +401,7 @@ fn parse_wasm_features(features: &str) -> Result<wasmparser::WasmFeatures> {
         memory64: false,
     })
 }
-
-struct CraneliftFlag {
-    name: String,
-    value: String,
-}
-
-fn parse_cranelift_flag(name_and_value: &str) -> Result<CraneliftFlag> {
+fn parse_cranelift_flag(name_and_value: &str) -> Result<(String, String)> {
     let mut split = name_and_value.splitn(2, '=');
     let name = if let Some(name) = split.next() {
         name.to_string()
@@ -419,7 +413,7 @@ fn parse_cranelift_flag(name_and_value: &str) -> Result<CraneliftFlag> {
     } else {
         bail!("missing value in cranelift flag");
     };
-    Ok(CraneliftFlag { name, value })
+    Ok((name, value))
 }
 
 fn parse_target(s: &str) -> Result<Triple> {

tests/all/module.rs

@@ -16,14 +16,14 @@ fn caches_across_engines() {
 
     // differ in shared cranelift flags
     let res = Module::deserialize(
-        &Engine::new(&Config::new().cranelift_nan_canonicalization(true)).unwrap(),
+        &Engine::new(Config::new().cranelift_nan_canonicalization(true)).unwrap(),
         &bytes,
     );
     assert!(res.is_err());
 
     // differ in cranelift settings
     let res = Module::deserialize(
-        &Engine::new(&Config::new().cranelift_opt_level(OptLevel::None)).unwrap(),
+        &Engine::new(Config::new().cranelift_opt_level(OptLevel::None)).unwrap(),
         &bytes,
     );
     assert!(res.is_err());
@@ -31,7 +31,12 @@ fn caches_across_engines() {
     // Missing required cpu flags
     if cfg!(target_arch = "x86_64") {
         let res = Module::deserialize(
-            &Engine::new(&Config::new().cranelift_clear_cpu_flags()).unwrap(),
+            &Engine::new(
+                Config::new()
+                    .target(&target_lexicon::Triple::host().to_string())
+                    .unwrap(),
+            )
+            .unwrap(),
             &bytes,
         );
         assert!(res.is_err());