Gentoo gcc link time optimization software

Building gentoo linux with llvmclang phoronix forums. At the time, all those tags increased confusion, and imo made work harder. Is there a reason why not to use linktime optimization lto. I recently did a fresh install of funtoo optimized for core i7 and a recompile of the system to run phoronix benchmarks. In order to use lto we must first install llvm with the gold linker plugin so clang can pass the plugin flag to the. As always it was not without glitches but by now i was able to build almost everything with gcc4.

This can result in better optimization of packages but isnt standard behavior in gentoo yet. Consequently, the code starts to behave differently. For example libreoffice will take a lot of time to compile despite how many cores you will throw at him. The behavior of gcc has changed significantly since version 3.

As you can tell from the thread, quite a number of packages fail to build with it. To start viewing messages, select the forum that you want to visit from the selection below. Makes programmes larger, havent done any benchmarks. I think it may have to do with the new lto features go for linktime optimization improvements.

The page doesnt say anything about linktime optimization or the flto flag. Gentoo linux was named after the fastswimming gentoo penguin. The name was chosen to reflect the potential speed improvements of machinespecific optimization, which is a major feature of gentoo. Gcc 10 linktime optimization benchmarks on amd threadripper stemming from the recent news in fedora 32 potentially ltoing packages by default for better performance and not yet having checked on the linktime optimization performance of the indevelopment gcc 10, here is a fresh look at the possible performance. Linktime optimization lto is one of the most actively developed features of gcc. Gentoo forums view topic compiling world with llvmgcc. Building gentoo linux with llvmclang following this weekends news about linktime optimization support for the linux kernel, in the discussion that spawned, building the linux kernel with the llvmclang compiler was once again brought up. Since 2010, i am working on getting lto to work well with real world applications and with gcc4. You can always override the automatic decision to do linktime optimization by passing fnolto to the link command. I am stuck on building gcc 9 with lto use flag, because it is creating over 30 lto processes when i try to do so. I have only nine packages with failed with lto in my package. The page doesnt say anything about link time optimization or the flto flag. Skipping to these boundaries can increase performance as well as the size of the resulting code and data spaces.

It will take at least twice as long to build sysdevelgcc, but the resulting binaries will be 10% to 15% faster at compiling software. Great customization and optimization options use flags and package manager portage, but too much time consuming on tweaking, optimization and installation source compiling very good docs, even the inexperienced users will able to install and configure the system and basics with some effort. Gcc 9 was branched last friday see a partial list of changes and if all goes well, it will be released tomorrow. We will try to figure out how things really are with gcc. Jem matzan many people wonder if 64bit gnulinux offers any kind of performance increase over 32bit. The gentoo recommended kernel sources for a desktop system are, of course, syskernelgentoosources. Following is a tutorial that would help beginners to install gentoo for the first time. In this article, we will be enabling the gcc options marked with to use this code transformation, gcc has to be configured with withppl and withcloog to enable the graphite loop transformation infrastructure. People say that gcc gnu compiler collection cannot generate effective code compared to other proprietary compilers.

The post title is gcc6 related state of gentoo and not gentoo is dying. Linktime optimization to speed up the linux kernel. When building software with the performanceoriented feature, linktime optimizations are applied on recent versions of the gnu compiler collection that allow for inlining of functions. If this is your first visit, be sure to check out the faq by clicking the link above. When i enable link time optimization in gcc, the binaries produced become much larger. These are maintained by the gentoo developers, and patched to fix security vulnerabilities, functional problems, as well as to improve compatibility with rare system architectures.

The program is written in various parts, which are usually stored as separate. It will take a longer time to compile your code with this option, and in fact it should not be used systemwide with gcc 4. Gentoo package management is designed to be modular, portable, easy to maintain, and flexible. Unfortunately, it is generally not faster than compile time optimization, so its a tradeoff between overall build speed and the overall quality of optimizations for that build. Ive so far come across two more packages that wont compile. This expands the scope of interprocedural optimizations to encompass the whole program or, rather, everything that is visible at link time. So to me this is clearly a bug in their compiler linker. No, i havent tried gold with llvm since im not using link time optimization yet. You generally should specify the optimization options to be used for linktime optimization though gcc tries to be clever at guessing an optimization level to use from the options used at. The only important thing to keep in mind is that to enable linktime optimizations you need to use the gcc driver to perform the linkstep. Phoronix gcc graphite and lto benchmarks minds and machines. When i say a beginner to gentoo, i literally mean a beginner to gentoo and not a beginner to gnulinux. The text asked if gentoo is dying, the title is just gcc6 related state of gentoo, you know.

Enable software pipelining of innermost loops during selective scheduling. To exemplify, if gentoo is installed on a machine whose gccs chost is i686pclinuxgnu, and a distcc server is setup on another computer whose gccs chost is i486linuxgnu, then there is no need to be afraid that the results would be less optimal because of the strictly inferior subarchitecture of the remote compiler andor hardware. If link time optimization were as fast as compile time optimization, then it would obviate the need for compiler hints. Matthias maier 20170521 and later updates these old versions of toolchain packages binutils, gcc, glibc are no longer officially supported and are not suitable for general use. But as always in gentoo theres other options also available. The linking stage takes more time, you can mitigate this by using multiple threads flto n. Link time optimization gcc, the gnu compiler collection. Gcc then automatically performs linktime optimization if any of the objects involved were compiled with the flto. That will do a profile guided optimization build of gcc at optimization level 3 with tweaks for your cpu. If im unhappy, i can request a patch, by submitting a bug, or the other extreme of this software is a piece of. The linktime optimization feature defers optimizing the resulting executables to linking phase. Linktime optimizations are optimizations done by the compiler at linktime, when interprocedural optimizations can be applied against the entire codebase as a whole of whats being compiled rather than just the scope of a single source file being compiled at a time.

A gentoo portage configuration for building with o3, graphite, and lto. Enabling gcc graphite and lto on gentoo minds and machines. To make whole program optimization effective, it is necessary to make certain whole program. Ipo differs from other compiler optimization because it analyzes the entire program. Packages to rebuild after upgrading gcc on gentoo systems. I was looking at the optimization flags in the gcc manual and it looked pretty. It is thus time for me to write an update on recent developments in my favourite areas. Gentoo is dying would be a fact, but state of gentoo is a question. Because such a large proportion of the packages that make up most. Now, with link time optimization, the tiny function read from read.

So, how can gcc compiler produce more effective code. Optimize options using the gnu compiler collection gcc. Gccs linktime optimization support allows for creating faster generated binaries at the cost of increased compile times and greater system memory ram usage. But strace has an easy fix, just change the unrecognized bool type to an int and it compiles.

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