tmsriram added a comment. In https://reviews.llvm.org/D39079#905454, @joerg wrote:
> In https://reviews.llvm.org/D39079#905396, @rnk wrote: > > > In https://reviews.llvm.org/D39079#905372, @joerg wrote: > > > > > Why again is this a good idea? > > > > > > It saves the direct jump to the PLT, reducing icache pressure, which is a > > major cost in some workloads. > > > It also increases the pressure on the branch predictor, so it is not really > black and white. My experiments show that doing this improves performance of some our large workloads by upto 1% and it happens with a reduction in iTLB misses. > > >>> This is an even worse hack than -Bsymbolic, >> >> Personally, I would like to build LLVM with -Bsymbolic so that we can build >> LLVM as a DSO and load it from clang without regressing startup time, so I >> don't see what's so terrible about -Bsymbolic, especially for C++ programs. > > Qt5 tries that. Requires further hacks as the main binary must be compiled as > fully position independent code to not run into fun latter. Fun with copy > relocations is only part of it. > >> Anyway, LLVM already has an attribute, nonlazybind, and this just provides a >> flag to apply it to all declarations. It gives the user access to the >> GOTPCREL relocations that we, and loaders, already support. > > The loader doesn't see GOTPCREL anymore. It also requires a linker that > disassembles instructions, because it can't distinguish between a normal > pointer load and a call, to be able to optimize it. The linker can replace indirect calls via GOTPCREL with direct calls, both GOLD and BFD linker support this today. https://reviews.llvm.org/D39079 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
