From e19762b57c3ab2a17631ad02e3d80c8b33af854b Mon Sep 17 00:00:00 2001
From: Mark Mansi <markm@cs.wisc.edu>
Date: Sat, 7 Mar 2020 15:10:13 -0600
Subject: [PATCH] add some placeholder text, short intro

---
 src/backend/backend.md      | 16 ++++++++++++++++
 src/backend/lowering-mir.md |  3 +++
 src/backend/monomorph.md    |  7 +++++++
 3 files changed, 26 insertions(+)

diff --git a/src/backend/backend.md b/src/backend/backend.md
index 167391a8..cc477b3e 100644
--- a/src/backend/backend.md
+++ b/src/backend/backend.md
@@ -1 +1,17 @@
 # The Compiler Backend
+
+The _compiler backend_ refers to the parts of the compiler that turn rustc's
+MIR into actual executable code (e.g. an ELF or EXE binary) that can run on a
+processor. This is the last stage of compilation, and it has a few important
+parts:
+
+0. First, we need to collect the set of things to generate code for. In
+   particular, we need to find out which concrete types to substitute for
+   generic ones, since we need to generate code for the concrete types.
+   Generating code for the concrete types (i.e. emitting a copy of the code for
+   each concrete type) is called _monomorphization_, so the process of
+   collecting all the concrete types is called _monomorphization collection_.
+1. Next, we need to actually lower the MIR (which is generic) to a codegen IR
+   (usually LLVM IR; which is not generic) for each concrete type we collected.
+2. Finally, we need to invoke LLVM, which runs a bunch of optimization passes,
+   generates executable code, and links together an executable binary.
diff --git a/src/backend/lowering-mir.md b/src/backend/lowering-mir.md
index e69de29b..e3c13795 100644
--- a/src/backend/lowering-mir.md
+++ b/src/backend/lowering-mir.md
@@ -0,0 +1,3 @@
+# Lowering MIR to a Codegen IR
+
+TODO
diff --git a/src/backend/monomorph.md b/src/backend/monomorph.md
index fc54886f..eaf37f2e 100644
--- a/src/backend/monomorph.md
+++ b/src/backend/monomorph.md
@@ -1 +1,8 @@
 # Monomorphization
+
+TODO
+
+
+## Polymorphization
+
+TODO