[LLVMdev] Does LLVM optimize variable to constant value in the compiling time?

[Robert Sandra]

By optimization, do you mean enable the optimization whiling building llvm
or use optimization flag while using clang command to get the bitcode file?

In my case, I disable the optimization when I built llvm, and I use the
following command to get the bitcode:

clang -O0 -emit-llvm hello.c -c -o hello.bc

To run the pass:

opt -load ../../../Debug+Asserts/lib/Hello.so -hello < hello.bc > /dev/null

The llvm version I am using is 3.3svn.

Thanks.

On Fri, Feb 22, 2013 at 4:25 PM, Caldarale, Charles R <
Chuck.Caldarale at unisys.com> wrote:

> > From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> > On Behalf Of Robert Sandra
> > Subject: [LLVMdev] Does LLVM optimize variable to constant value in the
> compiling time?
>
> > Considering the following codes:
>
> > int x = 21;
> > if(x > 20) {
> >    p = &C;
> > } else {
> >    p = &E;
> > }
>
> > I looked into the bitcode that LLVM generates, it still considers the
> 'else'
> > branch, which will be never reached during the runtime.
>
> What version of LLVM?  What happens if you enable optimization?
>
>  - Chuck
>
>
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