[llvm-dev] Why does LLVM keep some loads in the loops even after applying the O3 optimization?

[Tim Northover via llvm-dev]

Hi Fami,


On Thu, 28 Mar 2019 at 14:17, Fami H via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> There are no other basic blocks in the loop.  I am wondering why the first load instruction (ldr r0, [r5]) is repeatedly executed in the loop while the load address (r5) is never changed in the loop body. Shouldn't this instruction be moved out of the loop as a result of -licm flag?

It's very difficult to say without the source. It's possible LLVM
thinks the fprintf call might modify memory at that address, but
that's only speculation.

Cheers.

Tim.