search for: optimisers

Hi all, I am trying to understand the effectiveness of various llvm optimisations when a language targets llvm (or C) as its backend. The following is my approach (please correct me if I did anything wrong): I am trying to explicitly control the optimisations passes in llvm. I disable optimisation in clang, but instead emit unoptimized llvm IR, and use opt to optimise that. These are what I

Have -O0 on your clang command line causes all functions to get marked with an 'optnone' attribute that prevents opt from being able to optimize them later. You should also add "-Xclang -disable-O0-optnone" to your command line. ~Craig On Thu, Sep 21, 2017 at 10:04 PM, Yi Lin via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hi all, > > I am trying to

Full_Name: Karsten Krug Version: 2.4.0 OS: Open Suse 10.0, Windows XP Submission from: (NULL) (88.134.13.50) I found a problem in the 'optimise' function for one dimensional optimisation. Example 1: Try to find a maximum of the function below with the use of 'optimise' in the interval [0,0.5]. The function follows a parabola and has two local maxima located at the margins of

I am often asked what optimisations "our" compiler performs at each level. But "our" compiler is actually CLang/LLVM which we have retargeted to our proprietary target. Most of the work we do is in maintaining our target specific backend. Certainly there are optimisations that we do to take best advantage of our instruction set during lowering and instruction selection, and

I noticed that there is a '-run-pass' argument for llc. I am wondering if I can do a similar approach with machine level optimisations/passes for llc. Are those passes optional (so I can turn them off)? And how can I get MIR format as llc expects with '-run-pass'? Thanks a lot. Cheers, Yi On 22/9/17 15:10, Craig Topper wrote: > Have -O0 on your clang command line causes

Right but then you'll have to call each opt level. Have u looked in the pass manager? On Jun 24, 2017 3:52 PM, "Sean Silva via llvm-dev" <llvm-dev at lists.llvm.org> wrote: > The most definitive list you can probably hope to get will be obtained by > passing -mllvm -debug-pass=Structure to a clang invocation. > > -- Sean Silva > > On Jun 24, 2017 7:10 AM,

On Mon, Jun 26, 2017 at 5:04 AM, ORiordan, Martin <martin.oriordan at intel.com > wrote: > Thanks Sean and Silva. > > > > I guess what I was seeking was a URL that I could point (non-compiler) > people at, but I guess no such reference exists. What I can do if > reference bot the source manager and use ‘-mllvm -debug-pass=Structure’ > for each optimisation level,

Hi there, I have a piece of Matlab code I use to optimise a trding strategy. If there are any Matlab/R specialists out there, I would appreciate your help in doing the exact same optimisation in R. I suspect I would use nlm() in R but am not sure where to define my constraints. I have attached my Matlab code below for reference. Many thanks. Constraints function [c,ceq]=TriskellConstraints(X)

I agree, it's much clearer, it just takes runs at multiple opt levels and therefore I don't find it to be a "one stop shop". On Jun 24, 2017 8:44 PM, "Sean Silva" <chisophugis at gmail.com> wrote: > Looking at PassManagerBuilder can be useful because there are sometimes > comments giving some idea of the intent of the particular choice of passes, > but

With LLVM v5.0, I found failures in some of the 'gcc.c-torture/execute' tests due to a change in the optimisation where undefined behaviour is involved. The tests that fail are the '20040409-[123].c' tests. The underlying failure is due to the optimisation of the following: int test2(int x) { return x + INT_MIN; } from using an ADD instruction to using an OR instruction.

Hi Sanjoy, Yes these are C tests (from 'gcc.c-torture/execute'), and as I indicated in my original message, the tests are not valid because the behaviour is undefined. However, it was while investigating these new failures in these tests that I realised that this optimisation existed. The optimisation itself is perfectly valid, but it does mean that integer underflow will no longer be

Hello, We have developed a compiler analysis for multi-threaded codes that identifies functions which do not modify global variables. Furthermore, the analysis checks that accesses performed before the function call, do not target the same location as accesses performed after the call (hence, the variables accessed before and after the call do not alias). We want to integrate this analysis

Greetings to All! Now I am trying to run speex on TI DSP... I need only coder+decoder+AEC. Bitrate 8000bps. Building with floating point support. What can i do, to reduce RAM consumption? I mean very serious RAM optimisations. Deleting not used structure fields, etc... May be I can do something with alloc... Help me to determine that it is possible to throw out. What is best result(in RAM

> As far as I know, ObjectFile is either COFF, ELF or MachO format, > statically compiled. But the pass manager for applying optimisation > passes works only on llvm-ir. I would not need to apply optimisations on the parts of the program in the object file. These are meant to be optimised beforehand. The only parts I want to run passes on are specific function that I know

Taking the address of a function inhibits optimisations for that function. Essentially any ABI changes are unavailable if we can't adjust the call site to match. The case of interest here is when a given function is called directly and indirectly, and we don't want the latter to impose a cost on the former. One approach to avoid the ABI constraint cost is to extract/outline the body of an

When I'm trying to understand how or why the back end does something I've found the -view-* options to llc to be useful. It's not ideal, because "clang" doesn't take those options, so I have to invoke first "clang" and then "llc", and sometimes that combination gives different final code from invoking just "clang", but usually I can construct

Hello, I would like to build samba at different optimisation levels with debug symbols, in order to test a static analysis tool I have developed. I have found the configure option "--enable-developer", which I presume enables debug symbols and sets optimisation to O0, however I would also like to be able to enable debug symbols and set the optimisation level to O2. I cannot find a way

On Fri, Jun 4, 2010 at 8:18 AM, Pekka Nikander <pekka.nikander at nomadiclab.com> wrote: > I am working on heavily optimising unusually static C++ code, and have encountered a situation where I basically want an optimiser that would speculatively unroll a loop to see if the first round of the loop could be optimised further.  (I happen to know that it is possible.)  The previous

I'm fairly new to LLVM, and am writing an optimisation pass to be run by 'opt'. However, i'd like this pass to be parameterisable; as such i'd like to be able to pass an option to it (preferably via the command line to 'opt'). e.g. so i can do something like this "opt -load mypass.so -MyPass=MyPassOption < inputfile.bc ..." (for example one thing I would

I have 2 similar servers. Since upgrading one from CentOS 5.5 to 6, disk write performance in kvm guest VMs is much worse. There are many, many posts about optimising kvm, many mentioning disk performance in CentOS 5 vs 6. I've tried various changes to speed up write performance, but northing's made a significant difference so far: - Install virtio disk drivers in guest - update the