[llvm-dev] opt: how to invoke optimizations manually?

[John Regehr via llvm-dev]

I feel like it might save people some significant time in the long run 
if opt printed a helpful little error message when it is instructed to 
run >0 transformation passes and also all functions it sees are optnone.

John



On 3/16/18 7:30 AM, Son Tuan VU via llvm-dev wrote:
> Hi,
> 
> You should add this option to the first command 
> *"-disable-O0-optnone"* so *clang -Xclang -disable-O0-optnone -emit-llvm 
> -S -o without_dce.ll test.c* then *opt -dce -S < without_dce.ll > 
> with_dce.ll*
> *
> *
> HTH,
> 
> Son Tuan Vu
> 
> On Fri, Mar 16, 2018 at 2:15 PM, HwJ via llvm-dev 
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> 
>     Hello,
> 
>     I'd like to measure the impact of optimizations.
>     Trying this (for DCE):
> 
>     * clang -S -emit-llvm test.c
>     * opt -S test.ll > without_dce.ll
>     * opt -S -dce test.ll > with_dce.ll
> 
>     gives without_dce.ll and with_dce.ll having the same content.
> 
>     How can you apply certain optimizations in a specified order?
> 
>     Best,
>     HwJ
> 
>     ---
> 
>     $ cat test.c
> 
>         int dce(int n) {
>              if ((n < 0) || (n >= 0))
>                  return 1;
> 
>              return 0;
>         }
> 
>     _______________________________________________
>     LLVM Developers mailing list
>     llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>     http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>     <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> 
> 
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>