Remove logging levels restrictions (#538)

* Fixes #537: Remove release mode logging levels restrictions;

* Add information about log's logging levels in the README;

cranelift/README.md

@@ -130,6 +130,22 @@ protection. Just something to think about.
 
 </details>
 
+<details>
+<summary>Log configuration</summary>
+
+Cranelift uses the `log` crate to log messages at various levels. It doesn't
+specify any maximal logging level, so embedders can choose what it should be;
+however, this can have an impact of Cranelift's code size. You can use `log`
+features to reduce the maximum logging level. For instance if you want to limit
+the level of logging to `warn` messages and above in release mode:
+
+```
+[dependency.log]
+...
+features = ["release_max_level_warn"]
+```
+</details>
+
 <details>
 <summary>Building the documentation</summary>
 

lib/codegen/Cargo.toml

@@ -18,7 +18,7 @@ failure = { version = "0.1.1", default-features = false, features = ["derive"] }
 failure_derive = { version = "0.1.1", default-features = false }
 hashmap_core = { version = "0.1.9", optional = true }
 target-lexicon = { version = "0.0.3", default-features = false }
-log = { version = "0.4.4", default-features = false, features = ["release_max_level_warn"] }
+log = { version = "0.4.4", default-features = false }
 # It is a goal of the cranelift-codegen crate to have minimal external dependencies.
 # Please don't add any unless they are essential to the task of creating binary
 # machine code. Integration tests that need external dependencies can be

lib/codegen/meta/src/cdsl/mod.rs

@@ -1,7 +1,7 @@
 //! Cranelift DSL classes.
 //!
 //! This module defines the classes that are used to define Cranelift
-//! instructions and other entitties.
+//! instructions and other entities.
 
 pub mod types;
 

lib/codegen/src/isa/registers.rs

@@ -151,7 +151,7 @@ pub struct RegClassData {
     /// first register unit in each allocatable register.
     pub mask: RegUnitMask,
 
-    /// The global `RegInfo` instance containing that this register class.
+    /// The global `RegInfo` instance containing this register class.
     pub info: &'static RegInfo,
 }
 

lib/frontend/Cargo.toml

@@ -12,7 +12,7 @@ readme = "README.md"
 [dependencies]
 cranelift-codegen = { path = "../codegen", version = "0.22.0", default-features = false }
 target-lexicon = { version = "0.0.3", default-features = false }
-log = { version = "0.4.4", default-features = false, features = ["release_max_level_warn"] }
+log = { version = "0.4.4", default-features = false }
 hashmap_core = { version = "0.1.9", optional = true }
 
 [features]

lib/module/Cargo.toml

@@ -14,7 +14,7 @@ cranelift-codegen = { path = "../codegen", version = "0.22.0", default-features
 cranelift-entity = { path = "../entity", version = "0.22.0", default-features = false }
 hashmap_core = { version = "0.1.9", optional = true }
 failure = "0.1.1"
-log = { version = "0.4.4", default-features = false, features = ["release_max_level_warn"] }
+log = { version = "0.4.4", default-features = false }
 
 [features]
 default = ["std"]

lib/wasm/Cargo.toml

@@ -18,7 +18,7 @@ hashmap_core = { version = "0.1.9", optional = true }
 failure = { version = "0.1.1", default-features = false, features = ["derive"] }
 failure_derive = { version = "0.1.1", default-features = false }
 target-lexicon = { version = "0.0.3", default-features = false }
-log = { version = "0.4.4", default-features = false, features = ["release_max_level_warn"] }
+log = { version = "0.4.4", default-features = false }
 
 [dev-dependencies]
 wabt = "0.6.0"