Changes between Version 2 and Version 3 of Commentary/Compiler/NewCodeGen

Timestamp:

11/02/07 04:17:48 (6 years ago)

Author:

simonpj

Comment:

--

Commentary/Compiler/NewCodeGen

@@ -12 +12 @@
    * Control-flow blocks: `Block`
    * Control-flow graphs: `Graph`[[BR]][[BR]]
- * '''`ZipCfgCmm`''' instantiates `ZipCfg` for Cmm, by defining types `Middle` and `Last` and using these to instantiate the polymorphic fields of `ZipCfg`.  It also defines a bunch of smart constructor (`mkJump`, `mkAssign`, mkCmmIfThenElse` etc) which make it easy to build Cmm.
+ * '''`ZipCfgCmm`''' instantiates `ZipCfg` for Cmm, by defining types `Middle` and `Last` and using these to instantiate the polymorphic fields of `ZipCfg`.  It also defines a bunch of smart constructor (`mkJump`, `mkAssign`, mkCmmIfThenElse` etc) which make it easy to build `CmmGraph`.
 
 Todo list:
-  * Get rid of `CmmFormals` on `LastJump` and `LastCall` in `ZipCfgCmm`
+  * Get rid of `CmmFormals` on `LastJump` and `LastCall` in `ZipCfgCmm` in favour of `CopyIn` and `CopyOut`.
+  * Change the C-- parser (which parses RTS .cmm files) to directly construct `CmmGraph`.  
 
 == The pipeline ==
 
- * Code generator converts STG to Cmm.
+ * Code generator converts STG to `CmmGraph`.
 
- * '''Simple control flow optimisation''' (implemented in `CmmContFlowOpt`)
-   * 
+ * '''Simple control flow optimisation''', implemented in `CmmContFlowOpt`:
+   * Branch chain elimination
+   * Remove unreachable blocks
+   * TODO: block concatenation.  branch to K; and this is the only use of K.
+   * Consider: block duplication.  branch to K; and K is a short block.  Branch chain elimination is just a special case of this.
+
+ * '''The Adams optimisation'''.  Given:
+{{{
+  call f returns to K
+  K: CopyIn retvals; goto L
+  L: <code>
+}}}
+ transform to 
+{{{
+  call f returns to L
+  L : CopyIn retvals; <code>
+}}}
+ ''and'' move `CopyOut` into L's other predecessors.  !ToDo: explain why this is a good thing.
+
+ * '''Proc-point analysis''' and '''transformation''', implemented in `CmmProcPointZ`.  (Adams version is `CmmProcPoint`.) The transfomation part adds a `CopyIn` to the front of each proc-point, which expresses the idea that proc-points use a standard entry convention. 
+
+ * '''Add spill/reload''', implemented in `CmmSpillReload`, to spill live C-- variables before a call and reload them afterwards.  The middle node of the result is `Middle` (from `ZipCfgCmm` extended with `Spill` and `Reload` constructors.  
+ Invariant: (something like) all variables in a block are gotten from `CopyIn` or `Reload`. 
+