search for: onlyreadsmemory

...ing to determine what it would take to get the X86 code generator to replace the call to sqrt with a sqrtsd instruction inline. It turns out that it could do exactly that, were it not for the fact that in the function visitUnaryFloatCall() at line 5514 in SelectionDAGBuilder.cpp, the result of !I.onlyReadsMemory() Is true, so the code is unable to replace the function call with an ISD::FSQRT SDNode. If I remove the above test, then the compiler will emit a sqrtsd instruction. I am hoping that someone might be able to comment on what onlyReadsMemory is supposed to do be doing in general and why it is retu...

Hi, GlobalsAA, during propagation of mod-ref behavior in the call graph, looks at library functions (in GlobalsAAResult::AnalyzeCallGraph: F->isDeclaration() check), for attributes, and if the function does not have the onlyReadsMemory attribute set, forgets it. I noticed that library functions such as malloc/realloc do not have the attributes doesNotAccessMemory or onlyReadsMemory respectively set (FunctionAttrs.cpp). This leads to a loss of GlobalsAA information in the caller (and its caller and so on). Aren't these attrib...

...it would take to get the X86 code generator to replace the call to sqrt with a sqrtsd instruction inline. > > It turns out that it could do exactly that, were it not for the fact that in the function visitUnaryFloatCall() at line 5514 in SelectionDAGBuilder.cpp, the result of > > !I.onlyReadsMemory() > > Is true, so the code is unable to replace the function call with an ISD::FSQRT SDNode. If I remove the above test, then the compiler will emit a sqrtsd instruction. > > I am hoping that someone might be able to comment on what onlyReadsMemory is supposed to do be doing in gene...

...vm.org> wrote: > >> Hi, >> >> GlobalsAA, during propagation of mod-ref behavior in the call graph, >> looks at library functions (in GlobalsAAResult::AnalyzeCallGraph: >> F->isDeclaration() check), for attributes, and if the function does not >> have the onlyReadsMemory attribute set, forgets it. >> >> I noticed that library functions such as malloc/realloc do not have the >> attributes doesNotAccessMemory or onlyReadsMemory respectively set >> (FunctionAttrs.cpp). This leads to a loss of GlobalsAA information in the >> caller (and it...

I am probably stating the obvious, but if the function is side-effect free (onlyReadsMemory) it is valid to remove it. But I am guessing that does not belong to this pass. On Wed, Aug 24, 2016 at 8:38 AM, Sanjoy Das via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Btw, looks like the bug is in runSCCP in > > for (BasicBlock::iterator BI = BB.begin(), E = BB.end();...

Hello, Is there a analysis pass which calculates the ModRefBehaviours OnlyReadsPointerArguments and OnlyAccessesPointerArguments? I tried to find one but so far I only saw that different AA's return OnlyReadsMemory and DoesNotAccessMemory if the readonly and readnone attributes are set. Best regards and thanks in advance, Johannes -- Johannes Doerfert Researcher / PhD Student Compiler Design Lab (Prof. Hack) Saarland University, Computer Science Building E1.3, Room 4.26 Tel. +49 (0)681 302-57521 : doe...

...t; wrote: > > > > > > > Hi, > > GlobalsAA, during propagation of mod-ref behavior in the call graph, > looks at library functions (in GlobalsAAResult::AnalyzeCallGraph: > F->isDeclaration() check), for attributes, and if the function does > not have the onlyReadsMemory attribute set, forgets it. > > > > I noticed that library functions such as malloc/realloc do not have > the attributes doesNotAccessMemory or onlyReadsMemory respectively > set (FunctionAttrs.cpp). This leads to a loss of GlobalsAA > information in the caller (and its calle...

...get the X86 code generator to replace the call to sqrt with a sqrtsd instruction inline. >> >> It turns out that it could do exactly that, were it not for the fact that in the function visitUnaryFloatCall() at line 5514 in SelectionDAGBuilder.cpp, the result of >> >> !I.onlyReadsMemory() >> >> Is true, so the code is unable to replace the function call with an ISD::FSQRT SDNode. If I remove the above test, then the compiler will emit a sqrtsd instruction. >> >> I am hoping that someone might be able to comment on what onlyReadsMemory is supposed to do...

From: Villmow, Micah Sent: Tuesday, November 06, 2012 1:37 PM To: 'llvm-dev at cs.uiuc.edu' Cc: Guo, Xiaoyi Subject: Bug in SelectionDAG visitTargetIntrinsic We ran into a problem where specifying IntrNoMem was causing our instruction selection to fail with target specific intrinsics. After looking into the code and ISel debug it looks like tablegen and SelectionDAG are using different

void SelectionDAGBuilder::visitTargetIntrinsic(const CallInst &I, - unsigned Intrinsic) { - bool HasChain = !I.doesNotAccessMemory(); - bool OnlyLoad = HasChain && I.onlyReadsMemory(); + unsigned Intrinsic) { + // Info is set by getTgtMemInstrinsic + TargetLowering::IntrinsicInfo Info; + bool IsTgtIntrinsic = TLI.getTgtMemIntrinsic(Info, I, Intrinsic); + bool HasChain = Info.readMem || Info.writeMem; + bool OnlyLoad = HasChain &...

...aph) if (F->isDeclaration()) { // Try to get mod/ref behaviour from function attributes. - if (F->doesNotAccessMemory()) { + if (F->doesNotAccessMemory() || F->onlyAccessesArgMemory()) { // Can't do better than that! } else if (F->onlyReadsMemory()) { FunctionEffect |= Ref; if (!F->isIntrinsic()) // This function might call back into the module and read a global - // consider every global as possibly being read by this function. FR.MayReadAnyGlobal = true; } else {...

...ph) if (F->isDeclaration()) { // Try to get mod/ref behaviour from function attributes. - if (F->doesNotAccessMemory()) { + if (F->doesNotAccessMemory() || F->onlyAccessesArgMemory()) { // Can't do better than that! } else if (F->onlyReadsMemory()) { FunctionEffect |= Ref; if (!F->isIntrinsic()) // This function might call back into the module and read a global - // consider every global as possibly being read by this function. FR.MayReadAnyGlobal = true; } else {...

...eclaration()) { > // Try to get mod/ref behaviour from function attributes. > - if (F->doesNotAccessMemory()) { > + if (F->doesNotAccessMemory() || F->onlyAccessesArgMemory()) { > // Can't do better than that! > } else if (F->onlyReadsMemory()) { > FunctionEffect |= Ref; > if (!F->isIntrinsic()) > // This function might call back into the module and read a global - > // consider every global as possibly being read by this function. > FR.MayReadAnyGlobal = tr...

...// Try to get mod/ref behaviour from function attributes. > > - if (F->doesNotAccessMemory()) { > > + if (F->doesNotAccessMemory() || > > F->onlyAccessesArgMemory()) { > > // Can't do better than that! > > } else if (F->onlyReadsMemory()) { > > FunctionEffect |= Ref; > > if (!F->isIntrinsic()) > > // This function might call back into the module and > > read a global - > > // consider every global as possibly being read by this > >...

...Try to get mod/ref behaviour from function attributes. >>> - if (F->doesNotAccessMemory()) { >>> + if (F->doesNotAccessMemory() || F->onlyAccessesArgMemory()) { >>> // Can't do better than that! >>> } else if (F->onlyReadsMemory()) { >>> FunctionEffect |= Ref; >>> if (!F->isIntrinsic()) >>> // This function might call back into the module and read a global - >>> // consider every global as possibly being read by this function. >>&g...

...etermine it's a must-alias of a set of things, we could do the same If we determine it's a must-alias of the live on entry def, etc If I understand correctly, the necessary info for fp in this example is: isMustAlias (CallSite argument a, Value a) && getModRefBehavior(CallSite)== onlyReadsMemory. So adding a MRI_MustMod is insufficient? Are we instead looking to set a MRI_Must bit, disjunct of MRI_Mod, and test for MRI_Ref&MRI_Must or MRI_Mod&MRI_Must? In getModRefInfo(CS, Loc), the MRI_Must bit would then be set if doesAccessArgPointees and ArgAlias == MustAlias for all Args, whi...

Hi Stephan, >> In order to perform this transform the optimizers would have to work out >> that sample does not modify any global state. This cannot be done without >> knowing the definition of sample, but you only provide a declaration. > > Which is why I am trying to supply this additional information in a > custom alias analysis pass, but it doesn't seem to

...> // Try to get mod/ref behaviour from function attributes. >> - if (F->doesNotAccessMemory()) { >> + if (F->doesNotAccessMemory() || F->onlyAccessesArgMemory()) { >> // Can't do better than that! >> } else if (F->onlyReadsMemory()) { >> FunctionEffect |= Ref; >> if (!F->isIntrinsic()) >> // This function might call back into the module and read a global - >> // consider every global as possibly being read by this function. >> FR.M...

...ehaviour from function attributes. > > > - if (F->doesNotAccessMemory()) { > > > + if (F->doesNotAccessMemory() || > > > F->onlyAccessesArgMemory()) { > > > // Can't do better than that! > > > } else if (F->onlyReadsMemory()) { > > > FunctionEffect |= Ref; > > > if (!F->isIntrinsic()) > > > // This function might call back into the module and > > > read a global - > > > // consider every global as possibly being re...

Hi Félix, Sanjoy Das wrote: > Félix Cloutier via llvm-dev wrote: > > Assuming that this is a bug, what are the next steps? > > Looks like you already have a very small test case -- have you tried > sticking it in a debugger to see why SCCP thinks removing the call is > okay? > > Alternatively, file a bug at llvm.org/bugs and someone will get to it. The third