search for: optimisation

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....

...ble 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 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...

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 the interval [0,0.5]. Please try the following code which performs this optimisation, produces a p...

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...

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 all functions to get marked > with an ...

...u 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, "Martin J. O'Riordan via llvm-dev" < > llvm-dev at lists.llvm.org> wrote: > > 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 a...

....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, and document that. The downside is that this > will continuously go out of data with each release. > Yeah, the nasty thing is that as each user of LLVM is running potentially different pass pipelines, we don't really have a good way to write a user-facing (or at least non-compil...

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) global objFunc_vol; [a,b] = objFunc_vol(X); c(1) = b-6.5; c(2) = std(X(:))-6.5; ceq = []; e...

...be obtained by >> passing -mllvm -debug-pass=Structure to a clang invocation. >> >> -- Sean Silva >> >> On Jun 24, 2017 7:10 AM, "Martin J. O'Riordan via llvm-dev" < >> llvm-dev at lists.llvm.org> wrote: >> >> 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 optimisatio...

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. The optimisation is ent...

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 detected on systems which have hardware for this purpose. My question is not about the validity of the optimisation - it's perfectly legitimate - but rather about whether a target ca...

...nalysis 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 within the existing analyses, such that standard compiler optimisations can use this info. Do you suggest that we change the getModRefInfo() or there is a better way to expose the no-aliasing information to the optimisations? If getModRefInfo() is the way to go, can you please indicate how to start? Where can I find documentation about the way getModRefInfo() works an...

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 optimisation)? Also i am going to use TI optimised FFT.

> 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 beforehand. > What you can do is to isolate the...

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 constr...

...nation gives different final code from invoking just "clang", but usually I can construct a simple example in which "clang" and "clang | llc" give the same output and then use -view-legalize-dags, etc with "llc". However, when I'm trying to understand an optimisation that happens (or doesn't happen) earlier on in the compiler I've found this approach sometimes doesn't work at all. If I invoke "clang" with no optimisation options then the optimisation I'm interested in has already happened before the bitcode is generated, but if I invok...

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 optimisa...

...te: > 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 optimisations that produce the loop in the first place already do a magical job (relying heavily on constant propagation), transforming cross-class tail recursion into the loop that I am now addressing. Hence, there is probably little than can be done in the previous optimisations. > > So, has anyone work...

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...

...figures for the hosts show that the CentOS 6 server is faster: 54 CentOS 5 Host 50 CentOS 5 Host 69 CentOS 6 host 70 CentOS 6 host Figures for a CentOS 6 guest running on the CentOS 5 host show that the performance hit is less than 50%: 30 CentOS 6 guest on CentOS 5 host with no optimisations 27 CentOS 6 guest on CentOS 5 host with no optimisations 32 CentOS 6 guest on CentOS 5 host with no optimisations Here are the figures a CentOS 6 guest running on the CentOS 6 host with various optimisations. Even with these optimisations, performance doesn't come close to the un-opt...