similar to: [LLVMdev] loop metdata instruction

On 2/25/2013 2:08 PM, Redmond, Paul wrote: > > I've been looking through past threads looking for an answer to why the loop metadata is attached to the loop latch branch. What is the reason for putting the metadata inside the loop rather than outside (for example on the branch into the loop header.) Latch is a branch to the header. What branch in particular do you have in mind? Loop

Hi, On 2013-02-25, at 5:11 PM, Krzysztof Parzyszek wrote: > On 2/25/2013 2:08 PM, Redmond, Paul wrote: >> >> I've been looking through past threads looking for an answer to why the loop metadata is attached to the loop latch branch. What is the reason for putting the metadata inside the loop rather than outside (for example on the branch into the loop header.) > >

Hi, I want to use loop unrolling pass, however, I find that loop unrolling will introduces conditional branch at end of every "unrolled" part. For example, consider the following code *void foo( int n, int array_x[])* *{* * for (int i=0; i < n; i++)* * array_x[i] = i; * *}* Then I use this command "opt-3.5 try.bc -mem2reg -loops -loop-simplify -loop-rotate -lcssa

Hi Xiangyang, The algorithm for loop unrolling was changed post-3.5 to do more what you'd expect. If you use 3.6 or 3.7 you'll likely get better results. Cheers, James On Thu, 20 Aug 2015 at 18:09 Philip Reames via llvm-dev < llvm-dev at lists.llvm.org> wrote: > On 08/20/2015 07:38 AM, Xiangyang Guo via llvm-dev wrote: > > Hi, > > I want to use loop unrolling

There's been some recent noise on the mailing list about requiring -fno-rtti; http://lists.llvm.org/pipermail/llvm-dev/2015-August/089010.html Could that be it? On Sat, Aug 22, 2015 at 12:21 AM, Xiangyang Guo via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hi, James and Philip, Thanks for your help. > > Based on your advice, I downloaded llvm-3.7. However, with this new

Hi, I just tried llvm-3.8 (LLVM SVN Repository). With this version, -fno-rtti can help me to compile my code and -irce can help me to do a better job for loop unrolling. However, I still have one question. If I use Clang to compile a piece of c++ code to .bc and then use 'opt -loop-rotate -loop-unroll -irce', I can get what I want. I mean, there is no conditional branch at the end of each

I like to propose a new loop multi versioning optimization for LICM. For now I kept this for LICM only, but it can be used in multiple places. The main motivation is to allow optimizations stuck because of memory alias dependencies. Most of the time when alias analysis is unsure about memory access and it says may-alias. This un surety from alias analysis restrict some of the memory based

Hi, Mehdi, For example, I have this very simple source code: void foo( int n, int array_x[]) { for (int i=0; i < n; i++) array_x[i] = i; } After I use "clang -emit-llvm -o bc_from_clang.bc -c try.cc", I get bc_from_clang.bc. With my code (using LLVM IRbuilder API), I get bc_from_api.bc. Attachment please find thse two files. I also past the IR here.

Hi, InstCombine canonicalizes index operands (unless they are into struct types) to pointer size. The comment says: "If we are using a wider index than needed for this platform, shrink it to what we need. If narrower, sign-extend it to what we need. This explicit cast can make subsequent optimizations more obvious.". For our architecture, the canonicalization is a bit

Thanks for your point that out. I just add DataLayout in my code such as "mod->setDataLayout("e-m:e-i64:64-f80:128-n8:16:32:64-S128");", still no luck. I'm really confused about this. Do I need to add more passes before -loop-unroll? On Sat, Aug 22, 2015 at 11:36 AM, Mehdi Amini <mehdi.amini at apple.com> wrote: > > On Aug 22, 2015, at 7:27 AM, Xiangyang

Hi I have this program in which fooBuf can only take on NULL or the address of local_fooBuf, and fooBuf and local_fooBuf have scope of the foo function. Therefore there is no way for the fooPtr argument to alias with fooBuf. However, LLVM basicaa and globalsmodref-aa say the 2 pointers may alias. I am thinking whether i should implement a limited form of point-to alias on the fooBuf pointer in

Hi, I often find myself staring at IR and wanting to look at the C source code it corresponds to. To do so, I look up the debug identifier for the given IR line, scroll to the bottom of the IR file to find the debug identifier, look at the debug location (source and column), and then look at the source file. Too many steps. What would be great is a tool that took two files, i.e., a .c file and a

Hi, On Fri, Dec 30, 2011 at 3:09 AM, Tobias Grosser <tobias at grosser.es> wrote: > As it seems my intuition is wrong, I am very eager to see and understand > an example where a search limit of 4000 is really needed. > To make the ball roll again, I attached a testcase that can be tuned to understand the impact on compile time for different sizes of a basic block. One can also

Sent from my iPhone... On Jun 25, 2013, at 8:14 AM, Hal Finkel <hfinkel at anl.gov> wrote: > ----- Original Message ----- >> >> >> >> On Jun 24, 2013, at 4:24 PM, Hal Finkel < hfinkel at anl.gov > wrote: >> >> >> >> >> Indvars should ideally preserve NSW flags whenever possible. However, >> we don't want to

Hi, Scalar evolution seems to be wrapping around the trip count in the following loop. void add (int *restrict a, int *restrict b, int *restrict c) { char i; for (i = 0; i < 255; i++) a[i] = b[i] + c[i]; } When I run scalar evolution on the bit code, I get a backedge-taken count which is obviously wrong. $> cat loop.ll ; Function Attrs: nounwind define void @add(i32* noalias

Hello, I'm using LLVM to reason about memory safety of programs. One goal is to prove that certain array accesses are always safe. Currently, one of these proofs fails because of a missing no-signed-wrap (nsw) flag. I found that it has been "lost" during the SimplifyIndVar pass. Here's the example: int foo(int a[]) { int sum = 0; for (int i = 0; i < 1000; ++i)

On 12/29/2011 06:32 PM, Hal Finkel wrote: > On Thu, 2011-12-29 at 15:00 +0100, Tobias Grosser wrote: >> On 12/14/2011 01:25 AM, Hal Finkel wrote: >> One thing that I would still like to have is a test case where >> bb-vectorize-search-limit is needed to avoid exponential compile time >> growth and another test case that is not optimized, if >>

----- Original Message ----- > > > > On Jun 24, 2013, at 4:24 PM, Hal Finkel < hfinkel at anl.gov > wrote: > > > > > Indvars should ideally preserve NSW flags whenever possible. However, > we don't want to rely on SCEV to preserve them. SCEV expressions are > implicitly reassociated and uniqued in a flow-insensitive universe > independent of the

Hi Ashutosh, Have you been following the recent Loop Access Analysis work? LAA was split out from the Loop Vectorizer that have been performing the kind of loop versioning that you describe. The main reason was to be able to share this functionality with other passes. Loop Access Analysis is an analysis pass that computes basic memory dependence and the runtime checks. The versioning decision

On 4 February 2013 18:25, Arnold Schwaighofer <aschwaighofer at apple.com>wrote: > For cases where this approach breaks really badly we could consider adding > a specialized api or parameters (like the type of a user/use). But we > should do so only as a last resort and backed by actual code that would > benefit from doing so. > Very sensible, more or less what I had in