From 014549aea8d61c36dbb498666779e600a6406d20 Mon Sep 17 00:00:00 2001
From: "simonpj@microsoft.com" <unknown>
Date: Thu, 12 Nov 2009 15:33:32 +0000
Subject: [PATCH] Comments only

---
 compiler/cmm/CmmSpillReload.hs |   31 +++++++++++++++++--------------
 compiler/cmm/cmm-notes         |   18 ++++++++++++++++++
 2 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/compiler/cmm/CmmSpillReload.hs b/compiler/cmm/CmmSpillReload.hs
index 1cdafa9..df05a65 100644
--- a/compiler/cmm/CmmSpillReload.hs
+++ b/compiler/cmm/CmmSpillReload.hs
@@ -31,20 +31,23 @@ import UniqSet
 import Data.Maybe
 import Prelude hiding (zip)
 
--- The point of this module is to insert spills and reloads to
--- establish the invariant that at a call (or at any proc point with
--- an established protocol) all live variables not expected in
--- registers are sitting on the stack.  We use a backward analysis to
--- insert spills and reloads.  It should be followed by a
--- forward transformation to sink reloads as deeply as possible, so as
--- to reduce register pressure.
-
--- A variable can be expected to be live in a register, live on the
--- stack, or both.  This analysis ensures that spills and reloads are
--- inserted as needed to make sure that every live variable needed
--- after a call is available on the stack.  Spills are pushed back to
--- their reaching definitions, but reloads are dropped wherever needed
--- and will have to be sunk by a later forward transformation.
+{- Note [Overview of spill/reload]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The point of this module is to insert spills and reloads to
+establish the invariant that at a call (or at any proc point with
+an established protocol) all live variables not expected in
+registers are sitting on the stack.  We use a backward analysis to
+insert spills and reloads.  It should be followed by a
+forward transformation to sink reloads as deeply as possible, so as
+to reduce register pressure.
+
+A variable can be expected to be live in a register, live on the
+stack, or both.  This analysis ensures that spills and reloads are
+inserted as needed to make sure that every live variable needed
+after a call is available on the stack.  Spills are pushed back to
+their reaching definitions, but reloads are dropped wherever needed
+and will have to be sunk by a later forward transformation.
+-}
 
 data DualLive = DualLive { on_stack :: RegSet, in_regs :: RegSet }
 
diff --git a/compiler/cmm/cmm-notes b/compiler/cmm/cmm-notes
index 2fab86f..823fd0a 100644
--- a/compiler/cmm/cmm-notes
+++ b/compiler/cmm/cmm-notes
@@ -2,6 +2,24 @@ Notes on new codegen (Sept 09)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Things to do:
+
+ - CmmContFlowOpt.runCmmContFlowOptZs is not called!
+ - Why is runCmmOpts called from HscMain?  Seems too "high up".
+   In fact HscMain calls (runCmmOpts cmmCfgOptsZ) which is what
+   runCmmContFlowOptZs does.  Tidy up!
+
+
+ - AsmCodeGen has a generic Cmm optimiser; move this into new pipeline
+
+ - AsmCodeGen has post-native-cg branch elimiator (shortCutBranches);
+   we ultimately want to share this with the Cmm branch eliminator.
+
+ - At the moment, references to global registers like Hp are "lowered" 
+   late (in AsmCodeGen.fixAssignTop and cmmToCmm). We should do this
+   early, in the new native codegen, much in the way that we lower 
+   calling conventions.  Might need to be a bit sophisticated about
+   aliasing.
+
  - Refactor Cmm so that it contains only shared stuff
    Add a module MoribundCmm which contains stuff from
    Cmm for old code gen path
-- 
1.7.10.4