similar to: Ignored branch predictor hints

I did https://bugs.llvm.org/show_bug.cgi?id=37368 2018-05-09 20:33 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > I did > > https://bugs.llvm.org/show_bug.cgi?id=37368 > > 2018-05-09 20:29 GMT+02:00 David Zarzycki <dave at znu.io>: > >> I’d wager that the if-else chain is being converted to a "switch >> statement” during an optimization

Hi Dávid, Looks like you can defeat the switch conversion by adding a dummy asm(“”): #define likely(x) __builtin_expect((x),1) // switch like char * b(int e) { if (likely(e == 0)) return "0"; asm(""); if (e == 1) return "1"; else return "f"; } Dave > On May 9, 2018, at 2:33 PM, Dávid Bolvanský via llvm-dev

Thanks, interesting. But a fix needs to be made since branch predictor hints are broken in a valid C++20 code: https://godbolt.org/g/dpSDqd Dňa st 9. 5. 2018, 20:40 David Zarzycki <dave at znu.io> napísal(a): > Hi Dávid, > > Looks like you can defeat the switch conversion by adding a dummy asm(“”): > > #define likely(x) __builtin_expect((x),1) > > // switch like

Use *last = nullptr; for (Use &U : Src->uses()) last = &U; last->getUser()->dump(); Or any better solution? 2018-04-20 19:19 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > Is: > > > 2018-04-20 18:07 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > >> Hello, >> >> Code: https://godbolt.org/g/EG4Wi6

Maybe nicer.. auto i = Src->uses().begin(); std::advance(i, Src->getNumUses() - 1); i->getUser()->dump(); 2018-04-20 19:19 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > Use *last = nullptr; > for (Use &U : Src->uses()) > last = &U; > last->getUser()->dump(); > > > Or any better solution? > > 2018-04-20 19:19

It works with MemoryLocation MemoryLocation::get(const CallInst *CI) { AAMDNodes AATags; CI->getAAMetadata(AATags); const auto &DL = CI->getModule()->getDataLayout(); return MemoryLocation(CI, DL.getTypeStoreSize(CI->getType()), AATags); } Is it fine? :) 2018-05-22 23:56 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > Looks like there are many overloads

You might want to look more carefully at how you're constructing the MemoryLocation.   The first argument is a pointer, and the second argument is the number of bytes pointed to by that pointer (or MemoryLocation::UnknownSize if the number of bytes accessed isn't known). More generally, copy-pasting code you don't understand isn't a good idea. -Eli On 5/22/2018 4:02 PM, Dávid

IR: define i32 @calloc_strlen_write_between() { %call = tail call noalias i8* @calloc(i32 10, i32 1) store i8 97, i8* %call, align 1 %call1 = tail call i32 @strlen(i8* %call) ret i32 %call1 } static bool eliminateStrlen(CallInst *CI, BasicBlock::iterator &BBI, AliasAnalysis *AA, MemoryDependenceResults *MD, const DataLayout &DL, const TargetLibraryInfo *TLI,

Yeah, sorry for that. Better "It compiles ok (but maybe incorrect code)", not "It works" as I wrote. 2018-05-23 1:08 GMT+02:00 Friedman, Eli <efriedma at codeaurora.org>: > You might want to look more carefully at how you're constructing the > MemoryLocation. The first argument is a pointer, and the second argument > is the number of bytes pointed to by

Hello, Code: https://godbolt.org/g/EG4Wi6 unsigned fff3(void) { char buf[10] = ""; return strlen(buf); } Since we are memset-ing before strlen call, we could replace strlen with just 0. Has LLVM any API to get "last instruction before strlen" which modifies strlen argument "buf"? So we can check "yes, it is memset there, replace strlen with zero"

Full stack trace: opt: /home/xbolva00/LLVM/llvm/include/llvm/ADT/Optional.h:176: T* llvm::Optional<T>::getPointer() [with T = llvm::MemoryLocation]: Assertion `Storage.hasVal' failed. Stack dump: 0. Program arguments: opt aaa.ll -dse -S 1. Running pass 'Function Pass Manager' on module 'aaa.ll'. 2. Running pass 'Dead Store Elimination' on function

Looks like there are many overloads for "get". http://llvm.org/doxygen/MemoryLocation_8cpp_source.html But nothing for CallInst. Any suggestions how to do a proper one? I will look at it too. 2018-05-22 23:34 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > Full stack trace: > > opt: /home/xbolva00/LLVM/llvm/include/llvm/ADT/Optional.h:176: T* >

Is: 2018-04-20 18:07 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > Hello, > > Code: https://godbolt.org/g/EG4Wi6 > > unsigned fff3(void) { > char buf[10] = ""; > return strlen(buf); > } > > Since we are memset-ing before strlen call, we could replace strlen with > just 0. > > Has LLVM any API to get "last

* if (isStringFromCalloc(Dst, TLI)) should be if (!isStringFromCalloc(Dst, TLI)) but still asserting... 2018-05-22 23:06 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > Can you help a bit? > > I try to work with DSE but I got the following assert: > opt: /home/xbolva00/LLVM/llvm/include/llvm/ADT/Optional.h:176: T* > llvm::Optional<T>::getPointer() [with T

There is a new discussion related to -Wredundant-move warning on GCC bugzilla. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87300 pi 14. 9. 2018 o 9:53 David Blaikie <dblaikie at gmail.com> napísal(a): > > > On Fri, Sep 14, 2018 at 12:48 AM Stephan Bergmann <sbergman at redhat.com> > wrote: > >> On 13/09/2018 18:22, David Blaikie via llvm-dev wrote: >>

Yes, we should produce this warning in C++11 mode too. (I could be misrecalling, but I think the rationale for the current behaviour is based on historical GCC behaviour.) On Sun, 16 Sep 2018, 10:04 David Blaikie via cfe-dev, < cfe-dev at lists.llvm.org> wrote: > Fair point made on that thread - that this is a DR, so technically the > std::move is pessimizing even in C++11 mode.

It looks like the memoryIsNotModifiedBetween assumes the second argument is a store, or some other instruction supported by MemoryLocation::get.  If you're passing in something else, you'll have to compute the MemoryLocation some other way. (Generally, if you're asking a question about an assertion, please include the whole stack trace; it's hard to guess what's happening

Hello, I am currently working with the implementation of CFL Andersen algorithmand I am trying to do some improvements to the Andersen algorithm. I would like to create loadable module .so and run clang with my e.g. "cfl-anders-improved.so" to avoid the "long" way - generating IR, running opt with my improved algorithm to generate optimalized code and then building it. Is a

memoryIsNotModifiedBetween is precisely the sort of expensive walk we shouldn't be doing... I'm surprised it hasn't caused any serious issues yet.  Ideally, what we should be doing is using MemorySSA to find a dependency from the memset: if the closest dependency is the malloc, there aren't any stores between the memset and the malloc.  (But we aren't using MemorySSA in

Hello, Code: int f1(int a, int b) { return sqrt(a) > sqrt(b); } int f2(int a, int b) { return a > b; } Possibly, under -ffast-math (to ignore NaNs), f1 could be transformed to f2 variant. Also a transformation could support sin and tan, and reverse comparison for cos. Suggestions? Thanks -------------- next part -------------- An HTML attachment was scrubbed... URL: