search for: memoryisnotmodifiedbetween

...st = CI->getOperand(0); > Instruction *UnderlyingPointer = dyn_cast<Instruction>(GetUnderlyingObject(Dst, DL)); > if (!UnderlyingPointer) > return false; > if (isStringFromCalloc(Dst, TLI)) > return false; > errs() << "before\n"; > if (memoryIsNotModifiedBetween(UnderlyingPointer, CI, AA)) { <--- CRASH > errs() << "after\n"; > } > return false; > } > > Do you know what is wrong here? I followed the "example" (in eliminateNoopStore) how to use "memoryIsNotModifiedBetween". > > > Thank...

...b7 (opt+0x1b57bb7) #14 0x000056135d175216 (opt+0x6b0216) #15 0x00007f6e348051c1 __libc_start_main /build/glibc-itYbWN/glibc-2.26/csu/../csu/libc-start.c:342:0 #16 0x000056135d1f404a (opt+0x72f04a) 2018-05-22 23:32 GMT+02:00 Friedman, Eli <efriedma at codeaurora.org>: > 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...

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 bet...

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 s...

...0x00007f6e348051c1 __libc_start_main /build/glibc-itYbWN/glibc-2.26 >> /csu/../csu/libc-start.c:342:0 >> #16 0x000056135d1f404a (opt+0x72f04a) >> >> >> 2018-05-22 23:32 GMT+02:00 Friedman, Eli <efriedma at codeaurora.org>: >> >>> 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 aski...

...rlen) return false; Value *Dst = CI->getOperand(0); Instruction *UnderlyingPointer = dyn_cast<Instruction>(GetUnderlyingObject(Dst, DL)); if (!UnderlyingPointer) return false; if (isStringFromCalloc(Dst, TLI)) return false; errs() << "before\n"; if (memoryIsNotModifiedBetween(UnderlyingPointer, CI, AA)) { <--- CRASH errs() << "after\n"; } return false; } Do you know what is wrong here? I followed the "example" (in eliminateNoopStore) how to use "memoryIsNotModifiedBetween". Thank you for advice 2018-05-21 21:06 GMT+02...

...Func_strlen) > return false; > > Value *Dst = CI->getOperand(0); > Instruction *UnderlyingPointer = > dyn_cast<Instruction>(GetUnderlyingObject(Dst, DL)); > if (!UnderlyingPointer) > return false; > if (!isStringFromCalloc(Dst, TLI)) > return false; > > if (memoryIsNotModifiedBetween(UnderlyingPointer, CI, AA)) { > Value *Len = ConstantInt::get(CI->getType(), 0); > CI->replaceAllUsesWith(Len); > CI->eraseFromParent(); > return true; > } > return false; > } > > > ------------------------------------------------------ > That IR is still w...

...5216 (opt+0x6b0216) > #15 0x00007f6e348051c1 __libc_start_main /build/glibc-itYbWN/glibc-2. > 26/csu/../csu/libc-start.c:342:0 > #16 0x000056135d1f404a (opt+0x72f04a) > > > 2018-05-22 23:32 GMT+02:00 Friedman, Eli <efriedma at codeaurora.org>: > >> 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...

...c(*Callee, Func) || !TLI->has(Func) || Func != LibFunc_strlen) return false; Value *Dst = CI->getOperand(0); Instruction *UnderlyingPointer = dyn_cast<Instruction>(GetUnderlyingObject(Dst, DL)); if (!UnderlyingPointer) return false; if (!isStringFromCalloc(Dst, TLI)) return false; if (memoryIsNotModifiedBetween(UnderlyingPointer, CI, AA)) { Value *Len = ConstantInt::get(CI->getType(), 0); CI->replaceAllUsesWith(Len); CI->eraseFromParent(); return true; } return false; } ------------------------------------------------------ That IR is still wrongly transformed with this code to ret i32 0 (but t...

...Func_strlen) > return false; > > Value *Dst = CI->getOperand(0); > Instruction *UnderlyingPointer = > dyn_cast<Instruction>(GetUnderlyingObject(Dst, DL)); > if (!UnderlyingPointer) > return false; > if (!isStringFromCalloc(Dst, TLI)) > return false; > > if (memoryIsNotModifiedBetween(UnderlyingPointer, CI, AA)) { > Value *Len = ConstantInt::get(CI->getType(), 0); > CI->replaceAllUsesWith(Len); > CI->eraseFromParent(); > return true; > } > return false; > } > > > ------------------------------------------------------ > That IR is still w...

"memory accesses between the malloc and the memset without an expensive linear scan of the block/function" (1) do you mean just use "memoryIsNotModifiedBetween" function in DSE to check it? x = maloc(..); memset(x, ...) (2) GetUnderlyingObject would give me Value * (from malloc) ? Also another case: memset(s, 0, len); // len > 1 return strlen(s); // optimize to 0 (3) How to check memset and strlen pairs? I have a strlen call, I have a "V...

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