[LLVMdev] sccp pass with opt

Daniel Berlin
Tue, 16 Apr 2013 21:11:43 -0000

Right reason, but you want mem2reg.
Without mem2reg, i would not expect most passes to do anything.
opt a.ll -mem2reg -sccp gives the result you want.


On Tue, Apr 16, 2013 at 12:57 PM, Shuxin Yang <shuxin.llvm at gmail.com>
wrote:
> This compiler does not have mem-SSA,  as far as I know, only few pass can
> propagate value along memory.
>
> You need to promote those local variable into register first before sccp is
> invoked.
>  e.g1. opt a.ll -basicaa -gvn -sccp -S
>  eg.2. opt a.ll -sroa -sccp -S
>
>
> On 4/16/13 12:37 PM, Niko Zarzani wrote:
>
> Hi all,
>
> I am trying to see how single llvm optimizations work by running them one
by
> one with opt and looking how the IR changes.
> Since I was interested in seeing how constant propagation was working I
> tried to run opt on the Sparse Conditional Constant Propagation, however by
> passing as argument -S -sccp -die it does not change anything in the output
> IR code. I attached the file with the source code I used, I think that the
x
> value in that example should be propagated in the mul instruction. What am
I
> missing?
>
> Thank you in advance,
>
> Niko
>
>
>
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