LLVM in 20 minutes

1. LLVM
2009 1 15 ( )

2. LLVM
Tatsuhiro Ujihisa

3. LLVM
The Low Level Virtual Machine (LLVM) is a compiler
infrastructure, written in C++, which is designed for compile-
time, link-time, run-time, and "idle-time" optimization of
programs written in arbitrary programming languages. LLVM
was originally developed as a research infrastructure at the
University of Illinois at Urbana-Champaign to investigate
dynamic compilation techniques for static and dynamic
programming languages...
http://en.wikipedia.org/wiki/Low_Level_Virtual_Machine

4. In short,
C JVM
gcc
( )
( )

5. C
C→ → →
$ vim a.c
$ gcc a.c -S -o a.s
$ gcc a.s -o a
$ ./a

6. LLVM (1)
C → LLVM → LLVM →
$ vim a.c
$ llvm-gcc a.c -S -o a.ll
$ llvm-as a.ll -o a.bc
$ lli a.bc

7. LLVM (2)
C → LLVM → LLVM → →
$ vim a.c
$ llvm-gcc a.c -S -o a.ll
$ llvm-as a.ll -o a.bc
$ llc a.bc -o a
$ ./a

8. LLVM (3)
LLVM → LLVM →
$ vim a.ll
$ llvm-as a.ll -o a.bc
$ lli a.bc

9. LLVM (4)
LLVM → LLVM → →
$ vim a.ll
$ llvm-as a.ll -o a.bc
$ opt a.bc -o a2.bc
$ lli a2.bc

10. LLVM (5)
LLVM → LLVM → → →
$ vim a.ll
$ llvm-as a.ll -o a.bc
$ opt -O3 a.bc -o a2.bc
$ opt -O3 a2.bc -o a3.bc
$ lli a3.bc

11. LLVM
$ llvm-as a.ll -o a.bc
$ opt -O3 a.bc -o a2.bc
$ opt -O3 a2.bc -o a3.bc
$ llvm-dis a3.bc -o a3.ll
$ vim a3.ll

12. llvm-as: LLVM (.ll)
LLVM (.bc)
lli: LLVM (.bc)
opt: LLVM (.bc) LLVM
(.bc)
llvm-dis: llvm-as
llvm-gcc: C (.c) LLVM
(.ll)

13. LLVM Hello,
world!
Hello, world!
@str = internal constant [14 x i8] c"Hello, world!00"
declare i32 @puts(i8*)
define i32 @main()
{
call i32 @puts( i8* getelementptr ([14 x i8]* @str, i32
ret i32 0
}

14. LLVM
( )
C

15. Vim quickrun LLVM
.ll <Space>r llvm-as lli

16. LLVM
LLVM
OK (C OK)
LLVM Mac, Linux, Windows

17. LLVM ( )
C (llvm-gcc)
Perl
Python (pypy)
Ruby (Rubinius, MacRuby, etc)
Haskell
Brainf**k
... LLVM

18. LLVM
Pure
( )
Haskell
sudo port install pure

19. LLVM
LLVM
LLVM

20. ( )
LLVM
(MacRuby)
( svn up)

21. !
Brainf**k → LLVM
BFC: Brainf**k Compiler
git clone
git://github.com/ujihisa/bfc.git
vim bfc/bfc.rb

22. :+
+:
/* C */
/* char *h */
++*h;
LLVM !→
OK

23. (bfc.rb )
when '+'
a = tc += 1; b = tc += 1; c = tc += 1; d = tc += 1
"%tmp#{a} = load i32* %i, align 4n" <<
"%tmp#{b} = getelementptr [1024 x i8]* %h, i32 0, i32 %
"%tmp#{c} = load i8* %tmp#{b}, align 1n" <<
"%tmp#{d} = add i8 1, %tmp#{c}n" <<
"store i8 %tmp#{d}, i8* %tmp#{b}, align 1n"
1.
2.
3.
4. 1

24. $ cat helloworld.bf
$ cat helloworld.bf | ruby bfc.rb --llvm > helloworld.ll
$ llvm-as helloworld.ll > helloworld.bc
$ opt -O3 helloworld.bc #
$ lli helloworld.bc
Hello, world!
$ ruby bfc.rb --llvm helloworld.bf --run

25. :
BFC: Brainf**k Compilers
http://ujihisa.blogspot.com/2009/12/bfc-
brainfk-compilers.html
LLVM For Starters
http://ujihisa.blogspot.com/2009/12/llvm-
for-starters.html
Let's Try LLVM
http://ujihisa.blogspot.com/2009/12/let-
try-llvm.html

26. nil try-llvm.html