From 518d30b3793b57182a01afeca65879709da832ea Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <jolesen@mozilla.com>
Date: Fri, 17 Feb 2017 11:57:32 -0800
Subject: [PATCH] Add a compilation context struct.

This will provide main entry points for compiling functions, and it
serves as a place for keeping data structures that should be preserved
between function compilations to reduce allocator thrashing.

So far, Context is just basic scaffolding. More to be added.
---
 lib/cretonne/src/context.rs | 23 +++++++++++++++++++++++
 lib/cretonne/src/lib.rs     | 24 +++++++++++++-----------
 2 files changed, 36 insertions(+), 11 deletions(-)
 create mode 100644 lib/cretonne/src/context.rs

diff --git a/lib/cretonne/src/context.rs b/lib/cretonne/src/context.rs
new file mode 100644
index 0000000000..2360302ea2
--- /dev/null
+++ b/lib/cretonne/src/context.rs
@@ -0,0 +1,23 @@
+//! Cretonne compilation context and main entry point.
+//!
+//! When compiling many small functions, it is important to avoid repeatedly allocating and
+//! deallocating the data structures needed for compilation. The `Context` struct is used to hold
+//! on to memory allocations between function compilations.
+
+use ir::Function;
+
+/// Persistent data structures and compilation pipeline.
+pub struct Context {
+    /// The function we're compiling.
+    pub func: Function,
+}
+
+impl Context {
+    /// Allocate a new compilation context.
+    ///
+    /// The returned instance should be reused for compiling multiple functions in order to avoid
+    /// needless allocator thrashing.
+    pub fn new() -> Context {
+        Context { func: Function::new() }
+    }
+}
diff --git a/lib/cretonne/src/lib.rs b/lib/cretonne/src/lib.rs
index bfd986949a..47339a39ca 100644
--- a/lib/cretonne/src/lib.rs
+++ b/lib/cretonne/src/lib.rs
@@ -2,28 +2,30 @@
 
 #![deny(missing_docs)]
 
+pub use context::Context;
+pub use legalizer::legalize_function;
 pub use verifier::verify_function;
 pub use write::write_function;
-pub use legalizer::legalize_function;
 
 /// Version number of the cretonne crate.
 pub const VERSION: &'static str = env!("CARGO_PKG_VERSION");
 
-pub mod ir;
-pub mod isa;
 pub mod cfg;
 pub mod dominator_tree;
-pub mod entity_map;
 pub mod entity_list;
-pub mod sparse_map;
-pub mod settings;
-pub mod verifier;
+pub mod entity_map;
+pub mod ir;
+pub mod isa;
 pub mod regalloc;
+pub mod settings;
+pub mod sparse_map;
+pub mod verifier;
 
-mod write;
 mod constant_hash;
-mod predicates;
+mod context;
 mod legalizer;
-mod ref_slice;
-mod partition_slice;
 mod packed_option;
+mod partition_slice;
+mod predicates;
+mod ref_slice;
+mod write;