[LLVMdev] Suggestion on simple optimization pass for a beginner?

[David Tweed]

Hi,

 

If you're looking for something incredibly simple to get started with it
might be fruitful to implement replacement of particular function calls of
constant arguments with the appropriate result. (That might also then lead
to opportunities for a constant propagation pass.) This would involve quite
a bit of API usage without being actually that involved, and if you're doing
it just for the learning experience you probably neededn't bother too much
about the corner cases that make this tricky in general.

 

Cheers,

Dave

 

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Rekha R
Sent: 06 October 2013 13:24
To: LLVM Developers Mailing List
Subject: [LLVMdev] Suggestion on simple optimization pass for a beginner?

 

Hello,

I am a beginner in LLVM development with the aim of writing a new
optimization pass. But then before I could do that, I thought of writing
simple passes. I could successfully implement the Hello pass as given in the
doc. Then I wrote a simple Constant Folding pass - evaluate instructions of
the form c=10+20 and replace all uses of c with 30. Only later did I realize
that Clang does this optimization while building the IR. Hence I couldn't
check whether my constant folding pass is "working". I have two questions:

1. Is there a way to disable constant folding during IR development by
clang?

2. If not, can someone suggest a simple optimization (simple in complexity
on the lines of constant folding) to get started?

My intention is to get used to the APIs in LLVM and not get cluttered by the
optimization itself. (Hence I chose constant folding in the first place.)

Any opinion will be appreciated :)

Regards,

Rekha 
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