Current status; small fixes; more optimisation ideas in log

5 files changed, 94 insertions, 3 deletions

diff --git a/log.md b/log.md
index bee8491..b6ac3c4 100644
--- a/log.md
+++ b/log.md
@@ -618,3 +618,5 @@ need to look at register optimisations.
 
 - C calls
 - Capitalisation in the reference list
+- More optimisations: branch optimisation
+- More optimisations: tail recursion
diff --git a/thesis/intro.tex b/thesis/intro.tex
index 12a1484..f92b21d 100644
--- a/thesis/intro.tex
+++ b/thesis/intro.tex
@@ -52,7 +52,7 @@ ARM instructions have 4-bit register fields to address them.
 Some 16-bit Thumb instructions have 3-bit register fields that can only address the lowest eight registers.
 For these instructions there exist 32-bit variants that can address all sixteen registers.
 
-\begin{figure*}[t]
+\begin{figure*}[b]
 	\centering
 	\begin{subfigure}[b]{.2\linewidth}
 		\centering
@@ -312,6 +312,9 @@ There was a minor problem with negative offsets to the \ual{ldr} instruction,
 	that cannot be as large in Thumb as they can in ARM.
 \Cref{sec:load-offsets} deals with this.
 
+Moving to Thumb introduces a number of interesting optimisation vectors.
+One of them, register allocation, is discussed in \cref{sec:reg-alloc}.
+
 We benchmark the Thumb backend for Clean and discuss the results in \cref{sec:results}.
 
 \subsection{Terminology}
diff --git a/thesis/preamble.tex b/thesis/preamble.tex
index 9f07f6b..8d7dfed 100644
--- a/thesis/preamble.tex
+++ b/thesis/preamble.tex
@@ -66,6 +66,8 @@
 
 \let\oldtexttt\texttt
 \def\texttt#1{\oldtexttt{\footnotesize #1}}
+\let\oldurl\url
+\renewcommand{\url}[1]{{\small\oldurl{#1}}}
 
 \newcommand*{\blankpage}{%
 	\vspace*{\fill}
diff --git a/thesis/status.tex b/thesis/status.tex
new file mode 100644
index 0000000..29eff12
--- /dev/null
+++ b/thesis/status.tex
@@ -0,0 +1,85 @@
+\section{Current status}
+\label{sec:status}
+
+\begin{multicols}{2}
+
+In this section, we briefly discuss the current status of the Thumb backend for Clean.
+
+\subsection{Run-time system}
+\label{sec:status:rts}
+The latest version of the RTS can be found at \url{https://git.camilstaps.nl/clean-run-time-system.git/}.
+The Thumb backend is located in the \texttt{thumb2*} files and can be built with \texttt{Makefile.linux\_thumb2}.
+
+Register aliases have been used to ease changing the register allocation.
+The current allocation is set in \texttt{thumb2regs.s}.
+
+The Clean RTS has three garbage collectors:
+	a copying,
+	a compacting
+	and a marking collector.
+At this point only the first works.
+The expectation is that the others can be fixed rather easily and that only a few bits need to be flipped.
+We don't expect any problems other than the ones encountered in the copying collector (which has been discussed in \cref{sec:code-addresses}).
+
+\subsection{Code generator}
+\label{sec:status:cg}
+The latest version of the code generator can be found at \url{https://git.camilstaps.nl/clean-code-generator.git/}.
+The Thumb-specific part is in the \texttt{cgthumb2*} files and
+	throughout other files in a few \texttt{\#ifdef} blocks.
+It can be built with \texttt{Makefile.linux\_thumb2}.
+
+There are two code generators:
+	one that generates readable assembly code (\texttt{thumb2was.c})
+	and one that generates object code (\texttt{thumb2as.c}).
+At the moment of writing, only the first has been adapted to work for Thumb ---
+	the second is the same as the ARM code generator.
+
+\subsection{Building programs}
+\label{sec:status:building}
+To build a file \texttt{mymodule.icl} for a Thumb target, the following workflow can be used:
+
+\begin{minted}{bash}
+	# Build _system, needed only once
+	cg _system -s _system.s
+	as -o _system.o _system.s -march=armv7-a
+
+	# Build cgopts, needed only once
+	as -o cgopts.o cgopts.s -march=armv7-a
+
+	# Build actual program
+	clm -ABC mymodule
+	cg Clean\ System\ Files/mymodule -s mymodule.s
+	as -o mymodule.o mymodule.s -march=armv7-a
+	cc -o mymodule \
+		/path/to/rts/_startup.o \
+		/path/to/_system.o \
+		cgopts.o \
+		mymodule.o \
+		-lc -lm \
+		-march=armv7-a
+\end{minted}
+
+The \texttt{\_system.abc} that is needed can be taken from any Clean distribution \parencite{clean}.
+
+In \texttt{cgopts.s}, some variables are set that are normally added by the Clean make tool \texttt{clm}.
+The file may look like this:
+
+\begin{minted}{ual}
+		.data
+		.global ab_stack_size
+		.global flags
+		.global heap_size
+		.global heap_size_multiple
+		.global initial_heap_size
+
+	heap_size:          .word 0x00200000
+	ab_stack_size:      .word 0x00080000
+	flags:              .word 0x00000008
+	heap_size_multiple: .word 0x00001400
+	initial_heap_size:  .word 0x00019000
+\end{minted}
+
+Another option to build Clean programs using the Thumb backend is to get the Clean make tool \texttt{clm} from \url{https://svn.cs.ru.nl/repos/clean-tools/trunk/clm/} and build it so that \texttt{NO\_ASSEMBLE} is \emph{not} defined
+	(which will cause it to execute the readable code generator instead of the object code generator).
+
+\end{multicols}
diff --git a/thesis/thesis.tex b/thesis/thesis.tex
index 9e320c2..7ebb7ad 100644
--- a/thesis/thesis.tex
+++ b/thesis/thesis.tex
@@ -62,13 +62,12 @@ It produces on average 20\% smaller code than the ARM code generator, which is o
 \appendix
 \input{terms}
 \input{system}
+\input{status}
 
 \ifdraft\else
 \cleardoublepage
 \fi
 
-\let\oldurl\url
-\renewcommand{\url}[1]{{\small\oldurl{#1}}}
 % See http://tex.stackexchange.com/a/40750/23992
 \DeclareRobustCommand{\VAN}[1]{van #1}
 \phantomsection\addcontentsline{toc}{section}{\bibname}