On Tue, May 19, 2015 at 11:59 AM, Richard Henderson <r...@redhat.com> wrote: > On 05/19/2015 11:06 AM, Rich Felker wrote: >> I'm still mildly worried that concerns for supporting >> relaxation might lead to decisions not to optimize code in ways that >> would be difficult to relax (e.g. certain types of address load >> reordering or hoisting) but I don't understand GCC internals >> sufficiently to know if this concern is warranted or not. > > It is. The relaxation that HJ is working on requires that the reads from the > got not be hoisted. I'm not especially convinced that what he's working on is > a win. > > With LTO, the compiler can do the same job that he's attempting in the linker, > without an extra nop. Without LTO, leaving it to the linker means that you > can't hoist the load and hide the memory latency. >
My relax approach won't take away any optimization done by compiler. It simply turns indirect branch into direct branch with a nop prefix at link-time. I am having a hard time to understand why we shouldn't do it. -- H.J.
