similar to: [LLVMdev] difference between alias set tracker and alias analysis evaluator

Hi all, I have a problem with alias aliasing results returned by the alias set tracker and the alias analysis evaluator. so i call opt tool to run my module with the following options "-anders-aa -aa-eval -print-alias-sets -print-all-alias-modref-info" i use 2 classes to print alias analysis, the AliasSetTracket and AliasAnalysisEvaluator. but they give different results. here is a

Thanks, that's a lot more like the output I was expecting. But, I'm now wondering if I'm doing something wrong because the output confuses me. When run on the program: int main() { int a = 5; int* b = &a; int* c = &a; return *b; } I would expect to see either b may alias c or b must alias c. But, it doesn't even appear in the list. Furthermore, I would expect

Hi all, There is a problem about how AliasSetTracker merging AliasSet's when meet UnknownInst. When adding new pointer it looks for existing AliasSet's aliased with new pointer. And merging them together. It is ok for pointers: if %A mayalias %B and %B mayalias %C then %A mayalias %C. But the same logic when adding callsite is wrong ( findAliasSetForUnknownInst). Callsite may be known

Hi, all According to the document "LLVM Alias Analysis Infrastructure", I evaluated the AA performance by using the paramenters '-basicaa -ds-aa -anders-aa'. The source code 'test.c' is listed as follow: //------------=== Source code ===------------// #include<stdlib.h> typedef struct { int x; int y; } Location; Location* getNewLocation(int x, int y) {

Hi! On 7/10/2020 07:17, Shuai Wang wrote: > Hello! > > Thank you very much! Yes, that makes a lot of sense to me. However, just > want to point out two things that are still unclear: > > 1. The output contains a alias set of only one element, for instance: > "must alias, Mod       Pointers: (i32* %y, LocationSize::precise(4))" > > This one really confused

Hi, I am trying to get the alias info for the following code. The alias analysis returns "MayAlias" for arrays "A" and "B" in both the functions instead of "NoAlias". What passes should I run in opt before the alias analysis pass to get the accurate result? Example: //Note: static and called by func() only. static int sum(int *A, int *B) { int i = 0,

Hi, I'm trying to work with Type Based Alias Analysis (TBAA). Here's the example program I'm working with: ;;;;;;;;;;;;;;;;;;;;;; define void @foo(i64* %a, i64* %b, i64 %x, i64 %y) { store i64 %x, i64* %a, !tbaa !2 ; write to stack store i64 %y, i64* %b, !tbaa !3 ; write to heap ret void } !1 = !{!"root"} !2 = !{!"stack", !1} !3 = !{!"heap", !1}

BasicAA treats it conservatively if used on its own. It will return mayalias for the two pointers. TBAA operates based on the guarantee that pointers to different types cannot alias (think C's strict aliasing rules). Therein lies its power but also its danger, that is, nothing prevents the programmer to write code that violates these rules (That's why we have -fno-strict-aliasing). So

Dear LLVM, I would like to understand how to improve the LLVM alias analysis accuracy. I am currently using llvmgcc 2.9 and llvm 3.0. Here is the C code: void foo(int a[SIZE], int b[SIZE], int c[SIZE]) { for(int i=0; i<SIZE; i++) c[i] = a[i] + b[i]; } Here is the IR: target datalayout =

On Mon, 25 Jun 2007, Ben Chambers wrote: > I guess what confuses me is that it doesn't seem like it was able to > figure out that *b = a. Am I looking at this wrong? Is there a more > accurate way of getting the alias information out of the pass? The answer is to not look at the alias sets. I'd suggest looking at the raw results of alias queries. To do this, use the -aa-eval

Hi! I'm currently working on developing a new technique for alias analysis and wish to know how to compare it's results to the results that LLVM gets. The algorithm I have operates on LLVM assembly (I wrote the analysis in Haskell, so unfortunately I can't embed it into LLVM very easily). I tried using the option to print alias sets, but I'm not quite sure how to interpret the

Hi again! Replying in chronological order: > On Thu, Jul 9, 2020 at 6:51 PM Shuai Wang <wangshuai901 at gmail.com > <mailto:wangshuai901 at gmail.com>> wrote: > > Hey Matt, > > That's awesome. Thank you very much for all the information and > clarification! Just a few follow up questions. Could you kindly shed > some lights on it? Thank

Yes. I've attached an updated patch that does the following: 1. Fixes the partialalias of globals/arguments 2. Enables partialalias for cases where nothing has been unified to a global/argument 3. Fixes that select was unifying the condition to the other pieces (the condition does not need to be processed :P). This was causing unnecessary aliasing. 4. Adds a regression test to

Hello All, I have met a case with restrict keyword and I have a question about it. Let's look at a simple example. char buf[4]; void test(char *restrict a, char *restrict b, int count) {   for (unsigned i = 0; i < count; i++) {     *a = *b;     a++;     b++;     buf[i] = i;   } } I think there are no aliasing among pointers such as 'a', 'b' and 'buf'

to compile it to bitcode I give the following command : llvm-gcc -emit-llvm -c -o s.bc s.c and then I run different alias analysis passes like -anders-aa, -basicaa using following: opt -anders-aa -aa-eval -print-all-alias-modref-info s.bc From this I get the following output: Function: main: 8 pointers, 1 call sites NoAlias: i32* %retval, i32** %j NoAlias: i32* %retval, i32**

Oh, sorry, i didn't rebase it when i changed the fix, you would have had to apply the first on top of the second. Here is one against HEAD On Wed, Jan 14, 2015 at 12:32 PM, Ana Pazos <apazos at codeaurora.org> wrote: > Daniel, your patch does not apply cleanly. Are you on the tip? > > The code I see there is no line if (QueryResult == MayAlias|| QueryResult == PartialAlias)

Hey Matt, That's awesome. Thank you very much for all the information and clarification! Just a few follow up questions. Could you kindly shed some lights on it? Thank you! 1. I tried to tweak the code in the following way: - Clang [-> LLVM-IR]: https://llvm.godbolt.org/z/n9rGrs - [LLVM-IR ->] opt: https://llvm.godbolt.org/z/Uc6h5Y And i note that the outputs are: Alias sets for

----- Original Message ----- > From: "Daniel Berlin" <dberlin at dberlin.org> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Jiangning Liu" <Jiangning.Liu at arm.com>, "George Burgess IV" <george.burgess.iv at gmail.com>, "LLVM Developers > Mailing List" <llvmdev at cs.uiuc.edu>, "Nick Lewycky"

Hi Danny, // Add TypeBasedAliasAnalysis before BasicAliasAnalysis so that // BasicAliasAnalysis wins if they disagree. This is intended to help // support "obvious" type-punning idioms. - if (UseCFLAA) - addPass(createCFLAliasAnalysisPass()); addPass(createTypeBasedAliasAnalysisPass()); addPass(createScopedNoAliasAAPass()); + if (UseCFLAA) +

On Mon, Dec 5, 2011 at 6:08 PM, <ggan at codeaurora.org> wrote: > Hi Yi, > > I didn't get a chance to run your code. But from the debug information you > posted about tbaa alias analysis: > > Alias Set Tracker: 1 alias sets for 7 pointer values. >  AliasSet[0x207f860, 7] may alias, Mod/Ref   Pointers: (i32* %1, 4), > (i32* %x, 4), (i32** %p, 8), (i32** %q, 8),