similar to: [LLVMdev] SSA failed on alias

Hey, I am currently working on a VM which is based on LLVM and I would like to use its optimizer, but it somehow it can't detect something very simple (I guess.) This is the LLVM IR: target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128" target triple = "i386-unknown-linux-gnu" %struct.regs = type { i32, i32, i32 } define void @Test(%struct.regs* noalias

Hi, I have the following C loop to vectorize: struct box { double* source; }; void test(double* restrict result, struct box my_struct, int len) { for (int i=0 ; i<len; i++) { result[i] = my_struct.source[i] * my_struct.source[i]; } } There are two references in the loop, result[i] (restrict) and my_struct.source[i] (readonly). The compiler should easily figure out that

On Fri, Mar 13, 2015 at 2:54 PM Daniel Berlin <dberlin at dberlin.org> wrote: > On Fri, Mar 13, 2015 at 2:39 PM Olivier H Sallenave <ohsallen at us.ibm.com> > wrote: > >> Hi, >> >> I have the following C loop to vectorize: >> >> struct box { >> double* source; >> }; >> >> void test(double* restrict result, struct box

Hans Wennborg wrote: > After discussing with Nick Lewycky in the IRC channel, here comes a less > aggressive patch. > > We were worried that a constant pointer could alias with a GlobalValue. > Also, if one pointer could be a GlobalValue and the other a GlobalAlias > with the GlobalValue as aliasee. > However, I was not able to produce a test where this happens wihout the

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

After discussing with Nick Lewycky in the IRC channel, here comes a less aggressive patch. We were worried that a constant pointer could alias with a GlobalValue. Also, if one pointer could be a GlobalValue and the other a GlobalAlias with the GlobalValue as aliasee. However, I was not able to produce a test where this happens wihout the getUnderlyingObject() returning the same value. It

Dan Gohman wrote: > 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,

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 store is dead %x = load i32* inttoptr (i32 12345 to i32*) store i32 %x, i32* %p ret

On Mon, Jun 15, 2015 at 11:02 AM, Daniel Berlin <dberlin at dberlin.org> wrote: > Points-to analysis on LLVM-IR itself is fine (see the current CFL-AA, > or the old deleted andersen's implementations), and giving may-alias > and no-alias results also works. Giving must-alias answers, however, > is difficult. > > In particular, i would not simply ignore some types of

On 06/20/2017 03:26 AM, Hal Finkel wrote: > Hi, Adrien, Hello Hal! Thanks for your answer! > Thanks for reporting this. I recommend that you file a bug report at > https://bugs.llvm.org/ Will do! > Whenever I see reports of missed optimization opportunities in the face > of ptrtoint/inttoptr, my first question is: why are these instructions > present in the first place? At

LLVM 2.7's ScalarEvolution.cpp has this scary comment: // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can // lead to pointer expressions which cannot safely be expanded to GEPs, // because ScalarEvolution doesn't respect the GEP aliasing rules when // simplifying integer expressions. I think I understand what the comment is saying. If a GEP has

On Sun, Mar 15, 2015 at 4:34 PM Olivier Sallenave <ol.sall at gmail.com> wrote: > Hi Daniel, > > Thanks for your feedback. I would prefer not to write a new AA. Can't we > directly implement that traversal in BasicAA? > Can I ask why? Outside of the "well, it's another pass", i mean? BasicAA is stateless, so you can't cache, and you really don't

On Wed, Apr 20, 2011 at 8:08 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: > I have a question about when we should apply these pointer aliasing > rules. Do the rules tell us when a load/store is safe? > "Any memory access must be done through a pointer value associated > with an address range of the memory access, otherwise the behavior is > undefined." >

On Wed, Apr 20, 2011 at 12:20 PM, Eli Friedman <eli.friedman at gmail.com> wrote: > On Wed, Apr 20, 2011 at 8:08 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: >> I have a question about when we should apply these pointer aliasing >> rules. Do the rules tell us when a load/store is safe? >> "Any memory access must be done through a pointer value

On Wed, Apr 20, 2011 at 10:21 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: > On Wed, Apr 20, 2011 at 12:20 PM, Eli Friedman <eli.friedman at gmail.com> wrote: >> On Wed, Apr 20, 2011 at 8:08 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: >>> I have a question about when we should apply these pointer aliasing >>> rules. Do the rules tell

Hi again. I have a complex type system in my custom language that isn't easily representable as LLVM IR types, so I figured I could mostly get along with treating my types as i8* and doing the appropriate bitcasts and inttoptr instructions, and doing pointer arithmetic myself (by casting the pointers to ints, adding the appropriate byte offsets, and then casting back to pointers). However,

Hi, I am observing some incorrect behavior in basicaa, wherein two pointers that basicaa should determine to be MustAlias are ending up NoAlias - the other extreme :( I am blaming this on basicaa not handling inttoptr. Here is the relevant IR snippet. -------------------- %sunkaddr36 = ptrtoint %struct.BitParams* %bs to i32 %sunkaddr37 = add i32 %sunkaddr36, 16 %sunkaddr38 = inttoptr i32

On Wed, Apr 20, 2011 at 2:11 PM, Eli Friedman <eli.friedman at gmail.com> wrote: > On Wed, Apr 20, 2011 at 10:21 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: >> On Wed, Apr 20, 2011 at 12:20 PM, Eli Friedman <eli.friedman at gmail.com> wrote: >>> On Wed, Apr 20, 2011 at 8:08 AM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: >>>> I

On Sep 9, 2010, at 1:48 PM, David Greene wrote: > LLVM 2.7's ScalarEvolution.cpp has this scary comment: > > // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can > // lead to pointer expressions which cannot safely be expanded to GEPs, > // because ScalarEvolution doesn't respect the GEP aliasing rules when > // simplifying integer

Hi David, I had a quick look at the inttoptr/ptrtoint thing for GlobalISel and unless I am mistaken the semantic you want for such instructions do not match what the language reference says. Indeed, you said that inttoptr instruction is not a no-op on your architecture, whereas the language reference says: “The ‘inttoptr‘ instruction converts value to type ty2 by applying either a zero extension