search for: skaller

..., -O3, etc.) besides very high-level, extremely rough heuristics. > Another way to do this would be to calculate a time limit on > a pass and abort it if it exceeded the limit. No way. This would make the optimizations nondeterministic. -- Sean Silva On Thu, Nov 22, 2012 at 11:50 PM, john skaller <skaller at users.sourceforge.net> wrote: > Hi, I've been having some of the usual problems with C compiler optimisations: > they work fine on small functions but drop dead on big ones. > > I think this is roughly because some function level optimisations are > worse than O...

...f course Sean's point that superlinear behaviour ought to be reported as it's probably a bug is very true, Regards, Dave -----Original Message----- From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Sean Silva Sent: 23 November 2012 06:47 To: john skaller Cc: Clang; llvmdev at cs.uiuc.edu Subject: Re: [LLVMdev] [cfe-dev] costing optimisations Adding LLVMdev, since this is intimately related to the optimization passes. > I think this is roughly because some function level optimisations are > worse than O(N) in the number of instructions. Ple...

...aliasing -std=c++11 -fPIC .... Elapsed: 106.058, Result code 0 /usr/local/bin/clang++ -fno-common -fno-strict-aliasing -std=c++11 -dynamiclib -O3 .... Elapsed: 0.049, Result code 0 env DYLD_LIBRARY_PATH=build/release/lib/rtl:$DYLD_LIBRARY_PATH build/release/bin/flx_run '/Users/johnskaller/felix/test/regress/rt/tuple-02.dylib' Elapsed: 0.007, Result code 0 With -O2: Compile: Elapsed: 106.918, Result code 0 Link: Elapsed: 0.048, Result code 0 Run: Elapsed: 0.010, Result code 0 With -O1: Compile: Elapsed: 13.664, Result code 0 Link: Elapsed: 0.042, Result code 0...

On 23.11.2012, at 15:12, john skaller <skaller at users.sourceforge.net> wrote: > > On 23/11/2012, at 5:46 PM, Sean Silva wrote: > >> Adding LLVMdev, since this is intimately related to the optimization passes. >> >>> I think this is roughly because some function level optimisations are >>&...

...ly filled array provided int has a full representation. Historically, C was a real mess, with the most traditional copying of arrays of chars aliasing other values being undefined. C++ did NOT follow C here. It invented its own, more consistent, set of rules. Not sure about C++11 though. -- john skaller skaller at users.sourceforge.net http://felix-lang.org

Hello, I was wondering about the case below. I tried to find any information in C standard, but I found nothing. In this case, variable "i" is uninitialized, but it is the _same_ value passed as an argument, so only of "a" or "b" should be printed. What I found is that with -O2: LLVM (trunk) prints both "a" and "b" GCC (4.2) prints both

On 11/24/2012 02:08 AM, Jakub Staszak wrote: > Hello, > > I was wondering about the case below. I tried to find any information in C standard, but I found nothing. > In this case, variable "i" is uninitialized, but it is the _same_ value passed as an argument, so only of "a" or "b" should be printed. > > What I found is that with -O2: > LLVM

On 11/24/2012 04:14 AM, john skaller wrote: > > On 24/11/2012, at 10:21 PM, Nick Lewycky wrote: > >> >> Passing an uninitialized value as a function argument is undefined behaviour on the spot, regardless of what the callee does (even if it never references that argument). > > Cite reference? No? Then you...

...h a lower optimisation switch in that case. I think I might try that. > > Of course Sean's point that superlinear behaviour ought to be reported as > it's probably a bug is very true, Isn't data flow analysis O(N^3)? You cannot do proper alias analysis without it. -- john skaller skaller at users.sourceforge.net http://felix-lang.org