documentation missing for how to emit bitcode and machine code

[Quuxplusone]

Bugzilla Link	PR4343
Status	NEW
Importance	P normal
Reported by	John Nowak (john@johnnowak.com)
Reported on	2009-06-07 03:31:39 -0700
Last modified on	2010-03-06 13:59:17 -0800
Version	trunk
Hardware	PC All
CC	edwin+bugs@etorok.eu, llvm-bugs@lists.llvm.org, nicholas@mxc.ca
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[04:21am] johnnowak: where in the documentation does it discuss how to emit
bitcode and machine code?
[04:21am] johnnowak: i can't seem to track it down
[04:22am] ddunbar__: not sure if its in the actual docs
[04:23am] ddunbar__: see include/llvm/Bitcode/ReaderWriter.h though
[04:23am] johnnowak: you'd think discussing how to generate code would be part
of the documentation for a compiler infrastructure
[04:23am] ddunbar__: patches welcome!
[04:23am] ddunbar__: I thought the tutorial covered this stuff though
[04:24am] johnnowak: it doesn't
[04:24am] edwin: opt -load=yourplugin.so input.bc -o output.bc
[04:26am] johnnowak: i'd hope that you wouldn't want people unfamiliar with the
project submitting essential pieces of documentation for basic yet critical
functionality
[04:27am] ddunbar__: johnnowak: file a docs bug if you like

[Quuxplusone]

Do you mean:
 a) when running clang on the command line?
 b) when running llvm-gcc on the command line?
 c) given a .ll (textual LLVM IR) file, on the command line?
 d) from inside your LLVM-using C++ program?

The first three are well documented:
 a) http://clang.llvm.org/get_started.html
 b) http://llvm.org/cmds/llvmgcc.html
 c) i. To bitcode: http://llvm.org/cmds/llvm-as.html (described on http://llvm.org/docs/CommandGuide/ as "assemble a human-readable .ll file into bytecode")
    ii. To machine code: http://llvm.org/cmds/llc.html (described in the command guide as "generate native machine code for a bytecode file")

The last one however, is not.
 d) i. JITing is in the tutorial: http://llvm.org/docs/tutorial/LangImpl4.html#jit
    ii. To bitcode: Look at the source to llvm-as (it's only 149 lines). The important part is WriteBitcodeToFile() which is in the doxygen, but you'd have to know where to look: http://llvm.org/doxygen/namespacellvm.html#e74f76713a63766894166c9a8dd8e94a
    iii. To machine code: Look at the source to llc (364 lines). Sadly there's more than one function call needed to emit machine code.

So clearly that should be documented. But where? Add it to the tutorial? I
can't think of an obvious place this should go.

[Quuxplusone]

(In reply to comment #1)
> So clearly that should be documented. But where? Add it to the tutorial? I
> can't think of an obvious place this should go.
>

http://llvm.org/docs/tutorial/
Simple JIT Tutorials
4. Reading and Writing Bitcode
^ that looks like the obvious place to me.

[Quuxplusone]

(In reply to comment #1)
> Do you mean:
>  d) from inside your LLVM-using C++ program?

Yes, d. Török Edwin's suggestion seems appropriate.