Remove the Flags type from Config API (#769)

* Remove the `Flags` type from `Config` API

This commit removes the final foreign type from the `Config` API in the
`wasmtime` crate. The cranelift `Flags` type is now expanded into
various options on the `Config` structure itself, all prefixed with
`cranelift_` since they're only relevant to the Cranelift backend. The
various changes here were:

* The `avoid_div_traps` feature is enabled by default since it seemed
  that was done anywhere anyway.
* Enabling the wasm SIMD feature enables the requisite features in
  Cranelift as well.
* A method for enabling the debug verifier has been added.
* A method for configuring the Cranelift optimization level, as well as
  a corresponding enumeration, has been added.

* Assert that `Config` is both `Send` and `Sync`

src/bin/wasmtime.rs

@@ -36,7 +36,6 @@ use wasi_common::preopen_dir;
 use wasmtime::{Config, Engine, HostRef, Instance, Module, Store};
 use wasmtime_cli::pick_compilation_strategy;
 use wasmtime_environ::{cache_create_new_config, cache_init};
-use wasmtime_environ::{settings, settings::Configurable};
 use wasmtime_interface_types::ModuleData;
 use wasmtime_wasi::create_wasi_instance;
 use wasmtime_wasi::old::snapshot_0::create_wasi_instance as create_wasi_instance_snapshot_0;
@@ -231,29 +230,21 @@ fn main() -> Result<()> {
     }
 
     let mut config = Config::new();
-    let mut flag_builder = settings::builder();
-
-    // There are two possible traps for division, and this way
-    // we get the proper one if code traps.
-    flag_builder.enable("avoid_div_traps")?;
 
     // Enable/disable producing of debug info.
     config.debug_info(args.flag_g);
 
     // Enable verifier passes in debug mode.
-    if cfg!(debug_assertions) {
-        flag_builder.enable("enable_verifier")?;
-    }
+    config.cranelift_debug_verifier(cfg!(debug_assertions));
 
     // Enable SIMD if requested
     if args.flag_enable_simd {
-        flag_builder.enable("enable_simd")?;
         config.wasm_simd(true);
     }
 
     // Enable optimization if requested.
     if args.flag_optimize {
-        flag_builder.set("opt_level", "speed")?;
+        config.cranelift_opt_level(wasmtime::OptLevel::Speed);
     }
 
     // Decide how to compile.
@@ -261,7 +252,6 @@ fn main() -> Result<()> {
         args.flag_cranelift,
         args.flag_lightbeam,
     )?)?;
-    config.flags(settings::Flags::new(flag_builder));
     let engine = Engine::new(&config);
     let store = HostRef::new(Store::new(&engine));
 

src/bin/wast.rs

@@ -29,8 +29,6 @@ use std::path::Path;
 use std::process;
 use wasmtime::{Config, Engine, HostRef, Store};
 use wasmtime_cli::pick_compilation_strategy;
-use wasmtime_environ::settings;
-use wasmtime_environ::settings::Configurable;
 use wasmtime_environ::{cache_create_new_config, cache_init};
 use wasmtime_wast::WastContext;
 
@@ -118,25 +116,16 @@ fn main() -> Result<()> {
     }
 
     let mut cfg = Config::new();
-    let mut flag_builder = settings::builder();
-
-    // There are two possible traps for division, and this way
-    // we get the proper one if code traps.
-    flag_builder.enable("avoid_div_traps").unwrap();
-
     // Enable verifier passes in debug mode.
-    if cfg!(debug_assertions) {
-        flag_builder.enable("enable_verifier").unwrap();
-    }
+    cfg.cranelift_debug_verifier(cfg!(debug_assertions));
 
     // Enable optimization if requested.
     if args.flag_optimize {
-        flag_builder.set("opt_level", "speed").unwrap();
+        cfg.cranelift_opt_level(wasmtime::OptLevel::Speed);
     }
 
     // Enable SIMD if requested
     if args.flag_enable_simd {
-        flag_builder.enable("enable_simd").unwrap();
         cfg.wasm_simd(true);
     }
 
@@ -144,8 +133,7 @@ fn main() -> Result<()> {
     cfg.strategy(pick_compilation_strategy(
         args.flag_cranelift,
         args.flag_lightbeam,
-    )?)?
-    .flags(settings::Flags::new(flag_builder));
+    )?)?;
     let store = HostRef::new(Store::new(&Engine::new(&cfg)));
     let mut wast_context = WastContext::new(store);