skeleton for backend chapters

Author: mark-i-m

src/SUMMARY.md

@@ -101,13 +101,16 @@
     - [Constant evaluation](./const-eval.md)
         - [miri const evaluator](./miri.md)
     - [Parameter Environments](./param_env.md)
-    - [Code Generation](./codegen.md)
-        - [Updating LLVM](./codegen/updating-llvm.md)
-        - [Debugging LLVM](./codegen/debugging.md)
-        - [Backend Agnostic Codegen](./codegen/backend-agnostic.md)
-    - [Profile-guided Optimization](./profile-guided-optimization.md)
-    - [Sanitizers Support](./sanitizers.md)
-    - [Debugging Support in Rust Compiler](./debugging-support-in-rustc.md)
+    - [Compiler Backend](./backend/backend.md)
+        - [Monomorphization](./backend/monomorph.md)
+        - [Lowering MIR](./backend/lowering-mir.md)
+        - [Code Generation](./backend/codegen.md)
+            - [Updating LLVM](./backend/updating-llvm.md)
+            - [Debugging LLVM](./backend/debugging.md)
+            - [Backend Agnostic Codegen](./backend/backend-agnostic.md)
+        - [Profile-guided Optimization](./profile-guided-optimization.md)
+        - [Sanitizers Support](./sanitizers.md)
+        - [Debugging Support in Rust Compiler](./debugging-support-in-rustc.md)
 
 ---
 

src/codegen/backend-agnostic.md renamed to src/backend/backend-agnostic.md

@@ -0,0 +1 @@
+# The Compiler Backend

src/backend/backend.md

@@ -6,7 +6,7 @@ generates an executable binary. rustc uses LLVM for code generation.
 > NOTE: If you are looking for hints on how to debug code generation bugs,
 > please see [this section of the debugging chapter][debugging].
 
-[debugging]: codegen/debugging.html
+[debugging]: ./debugging.md
 
 ## What is LLVM?
 

src/codegen.md renamed to src/backend/codegen.md

@@ -3,7 +3,7 @@
 > NOTE: If you are looking for info about code generation, please see [this
 > chapter][codegen] instead.
 
-[codegen]: ../codegen.md
+[codegen]: ./codegen.md
 
 This section is about debugging compiler bugs in code generation (e.g. why the
 compiler generated some piece of code or crashed in LLVM).  LLVM is a big

src/codegen/debugging.md renamed to src/backend/debugging.md

@@ -0,0 +1 @@
+# Monomorphization

src/backend/lowering-mir.md

@@ -4,9 +4,8 @@
 This chapter contains a few tips to debug the compiler. These tips aim to be
 useful no matter what you are working on.  Some of the other chapters have
 advice about specific parts of the compiler (e.g. the [Queries Debugging and
-Testing
-chapter](./incrcomp-debugging.html) or
-the [LLVM Debugging chapter](./codegen/debugging.md)).
+Testing chapter](./incrcomp-debugging.html) or the [LLVM Debugging
+chapter](./backend/debugging.md)).
 
 ## `-Z` flags
 

src/backend/monomorph.md

@@ -23,7 +23,7 @@ it useful to look at the various codegen options listed under `-Chelp`
 and the internal options under `-Zhelp` -- there are a number that
 pertain to LLVM (just search for LLVM).
 
-[d]: ../codegen/debugging.md
+[d]: ../backend/debugging.md
 
 ## If you do narrow to an LLVM bug