similar to: Constants propagation into printf format string

On Thu, May 17, 2018 at 3:53 PM, Dávid Bolvanský via llvm-dev <llvm-dev at lists.llvm.org> wrote: > Hello, > > I was thinking about a new possible simplification in InstCombine which > would transform code like this: > > const char * NAME = "Prog"; > > void printer(char **arr, int len) { > for (int i = 0; i < len; ++i) { > printf("%s:

On 5/17/2018 4:04 PM, Davide Italiano via llvm-dev wrote: > On Thu, May 17, 2018 at 3:53 PM, Dávid Bolvanský via llvm-dev > <llvm-dev at lists.llvm.org> wrote: >> Hello, >> >> I was thinking about a new possible simplification in InstCombine which >> would transform code like this: >> >> const char * NAME = "Prog"; >> >> void

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

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

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

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

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

Hello, #define likely(x) __builtin_expect((x),1) // switch like char * b(int e) { if (likely(e == 0)) return "0"; else if (e == 1) return "1"; else return "f"; } GCC correctly prefers the first case: b(int): mov eax, OFFSET FLAT:.LC0 test edi, edi jne .L7 ret But Clang seems to ignore _builtin_expect hints in this case.

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

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

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,

* 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

It could save useless parsing in s/f/printf during runtime. E.g. for heavy "fprint"ing code like fprintf(f, "%s: %s", TAG, msg); I think it could be quite useful. After this transformation we would get fprintf(f, "ABC: %s", msg); --> We could save one push/mov instruction + less parsing in printf every time we call it. We would just replace string constant

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* >

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

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, I would like to find a way to do this removal properly. I found DSE and "eliminateNoopStore" can be useful for this thing. What I mean? int *test = malloc(15 * sizeof(int)); test[10] = 12; < ----- remove this store memset(test,0,sizeof(int) * 15); I already checked the function "eliminateNoopStore". Looks good, I think I would be to get the value ("A") we

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"

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: >>

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