similar to: [LLVMdev] [PATCH] Vectorizing Global Structures - Take 2

On Sat, Feb 16, 2013 at 8:26 AM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote: > Daniel, > > Indulge me one more mail and I will go away … (or I'll try to :) > > On Feb 15, 2013, at 6:38 PM, Daniel Berlin <dberlin at dberlin.org> wrote: > > yes, it does, but this is somewhat irrelevant to C. > > The pointers will not be of type struct.a[x] *,

Jeroen, thank you for very useful link with the context. Indeed union cases are very complicated and I see places in code when TBAA gives up. Daniel, I completely agree that TBAA has limited power and can solve relatively simple cases only. So anything more complicated that involves intermediate variables that points to struct or array elements cannot be solved by TBAA alone. Differentiating

BTW, I have found why it doesn't work for arrays. TBAA information propagation is not implemented in CodeGenFunction::EmitArraySubscriptExpr with "TODO: Preserve/extend path TBAA metadata?". On Fri, Dec 4, 2015 at 1:38 PM, Dmitry Polukhin <dmitry.polukhin at gmail.com> wrote: > As far as I can see it is specifics of arrays inside structs. Current TBAA > does distinguish

Hi Daniel, I see your point about LLVM and C/C++ type agnostic. I think TBAA was invented to partially cover this gap and give optimization opportunities when LLVM types are not sufficient but C/C++ types have required information. What do you think about following example: struct S { int a[10]; int b; }; int foo(struct S *ps, int i) { ps->a[i] = 1; ps->b = 2; return

Hi , The following loop fails to be vectorized since the load c[i] is casted as i64 and the store c[i] is double. The loop access analysis gives up since they are in different types. Since these two memory operations are in the same size, I believe the loop access analysis should return forward dependence and thus the loop can be vectorized. Any comments? Thanks, Jin #define N 1000 double

If I understand you correctly, conceptually you want two different objects to be returned for Foo.bl and Foo.al? Here is my take on this (take this with a grain of salt, Dan is the expert on this): http://llvm.org/docs/GetElementPtr.html#what-happens-if-an-array-index-is-out-of-bounds LLVM's semantic allows for arrays to be accessed out of bounds - this allows you to walk from the first

On Tue, Dec 19, 2017 at 9:10 AM, Siddharth Bhat via llvm-dev < llvm-dev at lists.llvm.org> wrote: > I could be entirely wrong, but from my understanding of memorySSA, each > def defines an "abstract heap state" which has the coarsest possible > definition - any write will be modelled as a "new heap state". > This is true for def-def relationships, but

Hi all, One of the reasons the Livermore Loops couldn't be vectorized is that it was using global structures to hold the arrays. Today, I'm investigating why is that so and how to fix it. My investigation brought me to LoopVectorizationLegality::canVectorizeMemory(): if (WriteObjects.count(*it)) { DEBUG(dbgs() << "LV: Found a possible read/write reorder:"

Hi Devs, I am looking at the bug https://bugs.llvm.org/show_bug.cgi?id=43953 and found that following piece of ir %arrayidx = getelementptr inbounds float, float* %Vec0, i64 %idxprom %0 = load float, float* %arrayidx, align 4, !tbaa !2 %arrayidx2 = getelementptr inbounds float, float* %Vec1, i64 %idxprom %1 = load float, float* %arrayidx2, align 4, !tbaa !2 %sub = fsub fast float %0, %1

Hi all, I have a question regarding dynamic indexing into a vector with GEP. I see that in the ScalarReplAggregates pass in the LLVM 3.2 release the call SROA::isSafeGEP() will now allow alloca scalarization in the case where a GEP index into a vector isn’t a constant. My question is: what is the expected behavior when the index is out of bounds of the vector? Is it undefined? I have an

Hi, It was a while now since I first asked about TBAA, and I am now getting back to this, trying to understand TBAA as it seems that the issue I described earlier originally in this thread is still one of many "TODO"s in CGExpr.cpp (http://lists.llvm.org/pipermail/llvm-dev/2018-September/126290.html). I would like to help on this to the best of my abilities, but I'm not quite

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:

before inlining all 20005 after inlining somewhere here changed made it NoAlias after Global Variable Optimizer 20014 20373 20255 20372 20254 before GVN 19993 20011 19991 20010 20030 It appears that TBAA metadata certainly changed after inlining and subsequent passes. I have attached the .bc file. I think I will try to dump out more TBAA metadata between passes. The method in

Hi Ivan, On 2019-01-17 18:09, Ivan Kosarev wrote: > Hello, Jonas, > > > It seems that when the struct member is an array, the base type > > becomes the element type. This is simply unhandled still in > > CodeGenTBAA ("TODO"). My question then is if it would be > > possible to instead create the DAG nodes !"A" and !"B" (as in > >

Hi Nadav, Thanks for the quick reply !! Ok, so as of now we are lacking capability to handle flat large reductions. I did go through function vectorizeChainsInBlock() (line number 2862). In this function, we try to vectorize if we have phi nodes in the IR (several if's check for phi nodes) i.e we try to construct tree that starts at chains. Any pointers on how to join multiple trees? I

Hi, I am trying to understand LLVM vectorization implementation and was looking into both loop and SLP vectorization. test case 1: *int foo(int *a) {int sum = 0,i;for(i=0; i<16; i++) sum += a[i];return sum;}* This code is vectorized by loop vectorizer where we calculate scalar loop cost as 4 and vector loop cost as 2. Since vector loop cost is less and above reduction is legal to

Thanks for quick reply Daniel, I tried to make a simple C testcase, but could not reproduce the same condition with output from Clang. I suppose I could modify the C code to make it look similar with TBAA's; I may be able to provide this by eod. > store %ptr above the load. My mistake; I was referring to the store $lcssa in bb2. Looking at the C source code, it should definitely alias

Hello everyone, In December, I had started a thread on scoped no-alias metadata in order to represent C99 'restrict' pointer information at the IR level: http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-December/056586.html At this point, we also have another important use case: preserving the existing 'noalias' attributes on pointers after inlining. My original proposal was

Hi Arnold, Thanks for your reply. I tried test case as suggested by you. *void foo(int *a, int *sum) {*sum = a[0]+a[1]+a[2]+a[3]+a[4]+a[5]+a[6]+a[7]+a[8]+a[9]+a[10]+a[11]+a[12]+a[13]+a[14]+a[15];}* so that it has a 'store' in its IR. *IR before vectorization :*target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128" target triple =

Hi, I am new to MemorySSA and wanted to understand its capabilities. Hence I wrote the following program (test.c): int N; void test(int *restrict a, int *restrict b, int *restrict c, int *restrict d, int *restrict e) { int i; for (i = 0; i < N; i = i + 5) { a[i] = b[i] + c[i]; } for (i = 0; i < N - 5; i = i + 5) { e[i] = a[i] * d[i]; } } I compiled this program using