similar to: [LLVMdev] [RFC] Scoped no-alias metadata (redux)

Hello again, When I had originally discussed this proposal, it was thought that we would not have to worry about control dependencies on the noalias metadata because such dependencies could only present a problem when loads or stores are merged (RAUW is called), and transformations should drop metadata when that happens. Now I'm worried that this is not true. Here's a simple example:

----- 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

----- Original Message ----- > From: "Chandler Carruth" <chandlerc at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Thursday, November 13, 2014 7:02:58 PM > Subject: Re: [LLVMdev] Upcoming Changes/Additions to Scoped-NoAlias metadata > > > >

Hi all, I'm having trouble understanding how llvm determines if pointers alias. Consider the following two functions that each do a redundant load: define float @A(float * noalias %ptr1) {   %ptr2 = getelementptr float* %ptr1, i32 1024   %val1a = load float* %ptr1   store float %val1a, float* %ptr2   %val1b = load float* %ptr1   ret float %val1b } define float @B(float * noalias %ptr1,

On Fri, Oct 7, 2011 at 2:15 PM, andrew adams <andrew.b.adams at gmail.com> wrote: > Hi all, > > I'm having trouble understanding how llvm determines if pointers > alias. Consider the following two functions that each do a redundant > load: > > define float @A(float * noalias %ptr1) { >   %ptr2 = getelementptr float* %ptr1, i32 1024 >   %val1a = load float*

It seems the same bug is there if we do pointer swapping with selects. Do you agree? (see example below) define void @f() { entry: %a1 = alloca float, align 4 %a2 = alloca float, align 4 br label %loop end: ret void loop: %phi = phi i32 [ 0, %entry ], [ 1, %loop ] %select_cond = icmp eq i32 %phi, 0 %ptr1 = select i1 %select_cond, float* %a1, float* %a2 %ptr2 = select i1

Alias analysis is figuring out the relationship between two pointer expressions, at some location in the program. At a given point in the program, do two expressions always refer to the same location? At a given point in the program, do two expressions never refer to the same location? AliasAnalysis::alias() doesn't explicitly take a "point" in the program because we don't

Oh. So it wasn't just the memory location size that was incorrect on those aliasing checks. I took a look at the tests and it appears that the alias call also catches some cases of restrict/noalias attributes, along with the tbaa info. My first idea of constructing an alias call with no Ptr's but valid tbaa info won't catch that at least. I will create a bug report and try and see if

----- 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

Hi Johannes, I followed your advice and got the same result: NoAlias and No dependence. Would you say AA is faulty for saying NoAlias or DA is faulty for saying no dependence? Or both? (revised example below) Thanks! define float @f() { entry: %g = alloca float, align 4 %h = alloca float, align 4 br label %for.body for.cond.cleanup: ; preds = %for.body

quite some speed improvement indeed. attached the updated patch to apply to svn/trunk. j -------------- next part -------------- A non-text attachment was scrubbed... Name: theora-mmx.patch.gz Type: application/x-gzip Size: 8648 bytes Desc: not available Url : http://lists.xiph.org/pipermail/theora-dev/attachments/20040824/5a5f2731/theora-mmx.patch-0001.bin

Hello, I've run into a problem which is both maddening and rather hard to replicate, therefore I wondered if someone might know of a plausible explanation for it. I couldn't find anything in the archives, though maybe I'm searching for the wrong thing. I'm calling some C code using .C, and get the vector I'm interested in back as the 7th location in the returned list.

----Snip-- struct st1{ int a; }; struct st2{ int b; }; struct st { struct st1 obj1; struct st2 obj2; }Obj; int test1(struct st1 * ptr1 , struct st2 * ptr2, struct st2 *ptr3) { ptr1->a = 10; *ptr3 = *ptr2; return ptr1->a; } --Snip--- For the above case GCC is able to store forward the value 10 to the return place. LLVM is not doing this. GCC https://godbolt.org/z/FCjCXy LLVM

The following is legal LLVM code in which ptr, ptr2, and ptr3 are all aliases: %struct = type { int, int } implementation int %p() { %ptr1 = alloca %struct %ptr2 = getelementptr %struct* %ptr1 %ptr3 = getelementptr %struct* %ptr2, uint 0 %pint = getelementptr %struct* %ptr3, uint 0, ubyte 0 %rval = load int* %pint ret int %rval } Should our pass a) ignore this, not replace %ptr1,

Hi, Following is excerpted from dynamic-vector-gep.ll. The resulting "extractelement" seems to always return 0.0f regardless the value idx1 and idx2 is holding. Am I missing something here or there is something fishy take place? Thanks Shuxin 101 ; CHECK: test6 102 ; CHECK: insertelement <4 x float> zeroinitializer, float 1.000000e+00, i32 %idx1 103 ; CHECK:

Hi everyone, As many of you might know, LLVM now has scoped noalias metadata (http://llvm.org/docs/LangRef.html#noalias-and-alias-scope-metadata) -- it allows us to preserve noalias function argument attributes when inlining, in addition to allowing frontends to add otherwise non-deducible aliasing properties to memory accesses. This currently works well, but needs a change and an intrinsic, as

Hi Danny, Thanks for that :) However I've just updated the prototype patch to NewGVN and it didn't need any API changes - all I rely on is GVNExpression. Hongbin, I wanted to explain a little about what GVNSink can currently do, what it was designed for and hopefully how to make it handle your testcase. *Background* Common code sinking is more difficult to efficently do than one might

Hi Matthijs, Sorry for not responding earlier. I have a few comments. On Aug 7, 2008, at 7:41 AM, Matthijs Kooijman wrote: > Hi Mon Ping, > > I've again attached a patch, wich lets LLVM know about about the > relations > between different address spaces. Instead of cramming this info in > with > TargetData (with all kinds of unwanted side effects, especially for

Hi Mon Ping, I've again attached a patch, wich lets LLVM know about about the relations between different address spaces. Instead of cramming this info in with TargetData (with all kinds of unwanted side effects, especially for the IR), I opted to create a new pass, TargetAddrspaces, which holds this information. Just like TargetData, this can be added to the passmanager by the tool running

Hi Shuxin I think i might have written that test. And yeah, no matter what values you get you’ll get a 0.0. Its probably a bad test case, but i can’t remember if it exposed a bug in this form or not. Since writing it Chandler rewrote SROA anyway so the original bug is long gone. Thanks, Pete On Apr 5, 2013, at 11:57 AM, Shuxin Yang <shuxin.llvm at gmail.com> wrote: > Hi, > >