similar to: [LLVMdev] Semantic of parameter attribute noalias

I wanted to confirm that my understanding of the situation is correct. For background, I've been working have an optimizer pass for a research architecture which works best when there are large basic blocks and good alias analysis results. I first noticed the issue in rgbcmy01 from eembc-1.1, but have created a simpler test case which demonstrates the same issue which is unencumbered by the

----- Original Message ----- > From: "Alex Bradbury" <asb at asbradbury.org> > To: llvm-dev at lists.llvm.org > Cc: "Hal Finkel" <hfinkel at anl.gov> > Sent: Sunday, November 8, 2015 10:30:09 AM > Subject: Re: noalias parameter attribute not currently exploited by alias analysis? > > On 2 November 2015 at 20:20, Alex Bradbury <asb at

----- Original Message ----- > From: "Raul Silvera" <rsilvera at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Chandler Carruth" <chandlerc at google.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Friday, November 14, 2014 12:15:51 PM > Subject: Re: [LLVMdev] Upcoming

----- Original Message ----- > From: "Raul Silvera" <rsilvera at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Chandler Carruth" <chandlerc at google.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Friday, November 14, 2014 10:34:39 AM > Subject: Re: [LLVMdev] Upcoming

Hi Daniel, On April 11, 2017 at 6:22:34 PM, Daniel Berlin (dberlin at dberlin.org) wrote: > Note: This is a generic problem with any situation where noalias exists but > the pointers are proven equal :) Yes. > TBAA, for example, has the same generic issue, we just drop the tbaa > metadata and declare it okay, even though it would have been UB at the > source level. Yes.  I

----- Original Message ----- > From: "Raul Silvera" <rsilvera at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Chandler Carruth" <chandlerc at google.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Tuesday, November 18, 2014 9:09:40 PM > Subject: Re: [LLVMdev] Upcoming

Regarding the name, I'm not sure noaliasAtFunctionEntry makes sense, for two reasons: a) The pointer involved may not be defined at entry. b) We already have something which is similar in spirit - IsIdentifiedObject. That covers the 3 cases I have in the new function, but also two additional ones: GlobalValues which are not GlobalAliases, and byval arguments. Unfortunately, a check of

Kuperstein, Michael M wrote: > Thanks Nick! > > Can you just check sanity before I commit? > (Or suggest a better name for the function...) Sure! +static bool canNotAliasDiffArgument(const Value *V) +{ + return (isa<AllocaInst>(V) || isNoAliasCall(V) || isNoAliasArgument(V)); +} Extra parens? The name "canNotAliasDiffArgument" works, but it's named for what we

Kuperstein, Michael M wrote: > Regarding the name, I'm not sure noaliasAtFunctionEntry makes sense, for two reasons: > a) The pointer involved may not be defined at entry. Right, I thought of that too. > b) We already have something which is similar in spirit - IsIdentifiedObject. That covers the 3 cases I have in the new function, but also two additional ones: GlobalValues which

----- Original Message ----- > From: "Raul Silvera" <rsilvera at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Chandler Carruth" <chandlerc at google.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Monday, November 24, 2014 7:20:04 PM > Subject: Re: [LLVMdev] Upcoming Changes/Additions

Thanks Nick! Can you just check sanity before I commit? (Or suggest a better name for the function...) -----Original Message----- From: Nick Lewycky [mailto:nicholas at mxc.ca] Sent: Sunday, May 26, 2013 09:54 To: Kuperstein, Michael M Cc: LLVMdev at cs.uiuc.edu Subject: Re: [LLVMdev] Mixing noalias and regular arguments Kuperstein, Michael M wrote: > Ping? Pong! Sorry for the slow review,

Hi all, I have a custom alias analysis pass that enforces that pointers from different address spaces do not alias, and I'm using MemoryDependenceAnalysis to, well, figure out dependence analysis. The AA pass is extremely simple, it only checks the address space of pointers, returns NoAlias if they're different, and delegates otherwise. It is the last alias analysis pass added to my

Kuperstein, Michael M wrote: > Ping? Pong! Sorry for the slow review, I had this patch starred but hadn't got around to it. Yes, the rationale and implementation are correct. > (Is there a code owner for AA, btw?) (It falls back on the more general code owner who is Chris Lattner in this case, "Everything not covered by someone else".) +/// isNoAliasArgument - Return true

Hi all, I think I've spotted a semantic issue with marking @malloc and @realloc as noalias.  Say we have the program: int f() {   int* p0 = malloc(size of(int));   free(p0);   int* p1 = malloc(sizeof(int));   if (!p1) return 20;   int value = 0;   for (int i = 0; i < 1; i++) {     *p1 = 20;     value = *p1;     if (false)  // "false" is obscured in a way the compiler can't

Thanks Daniel, I'll do a debug build of LLVM (I guess that'll teach me) and step through it as soon as I'll find a power outlet. I'm calling getDependency on the load instruction, and it returns the store instruction. Suspiciously enough, calling invalidateCachedPointerInfo on load->getPointerOperand() does not cause my AA pass to be called again when I use getDependency (or

On Nov 4, 2009, at 6:43 AM, Hans Wennborg wrote: > Here is another change I'd like to suggest to the BasicAliasAnalysis. > > LLVM fails to remove the dead store in the following code: > > %t = type { i32 } > > define void @f(%t* noalias nocapture %stuff ) { > %p = getelementptr inbounds %t* %stuff, i32 0, i32 0 > > store i32 1, i32* %p; <-- This

Hello, Currently the noalias attribute can be applied on function parameters and return value, or via scoped alias on store. The problem is that there is no easy way to apply the noalias attribute on a pointer that is loaded indirectly (e.g from the field of an aggregate, or from a memory location - though for this you can still use scoped alias, but they are a lot more intrusive) The idea

----- Original Message ----- > From: "Raul Silvera" <rsilvera at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Chandler Carruth" <chandlerc at google.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Tuesday, November 18, 2014 11:23:25 AM > Subject: Re: [LLVMdev] Upcoming

Hi, What are the intended semantics of noalias when applied to a vector of pointers? signext/zeroext parameter attributes are incorrectly rejected for vectors (bug 15391), and I'm not sure if the same is true for noalias when applied to pointer vectors. There's no mention of it in the langref, and the verifier currently rejects it. Is it supposed to work? Are pointers within the

On Tue, Apr 11, 2017 at 7:02 PM, Daniel Berlin <dberlin at dberlin.org> wrote: > >> >> > It would require semantic changes to llvm ir to fix this to properly >> > express object lifetimes that is compatible with all the random babble >> > standards have written down :) >> > For now, the only sane solution IMHO, is to say that no alias implies