search for: unrolled

I am starting to use the sample profiler to analyze new performance opportunities. The loop unroller has popped up in several of the benchmarks I'm running. In particular, libquantum. There is a ~12% opportunity when the runtime unroller is triggered. This helps functions like quantum_sigma_x (http://sourcecodebrowser.com/libquantum/0.2.4/gates_8c_source.html#l00149). The function accounts

Hi Hal, I did opt.exe -S -debug -loop-unroll -unroll-runtime=true -unroll-count=4 csShader.ll and it prints out: Args: opt.exe -S -debug -loop-unroll -unroll-runtime=true -unroll-count=4 csShader.ll Loop Unroll: F[build_cs_5_0] Loop %loop_entry Loop Size = 82 partially unrolling with count: 1 Thanks, Frances On Thu, Oct 15, 2015 at 9:35 PM, Hal Finkel <hfinkel at anl.gov>

...ves loop unrolling hint metadata after using it to avoid unrolling more than the hint suggests. This is a potential problem because loop unrolling can be run more than once. Example: a loop annotated with "#pragma clang loop unroll_count(2)" which adds hint metadata to the loop would be unrolled twice every time the loop unrolling pass is run. Anyway, I ask about metadata removal because Eli who is reviewing the patch wasn't sure whether this was acceptable. Loop unrolling metadata can take the following forms: llvm.loop.unroll.enable false // don't unroll llvm.loop.unroll.enabl...

Hi, I am trying to do loop unrolling with loops that don't have constant loop counter. It is highly appreciated if anyone can help me on this. What I want to do is to turn loop (n) { <loop body> } into loop (n/4) { <loop body> <loop body> <loop body> <loop body> } loop (n%4) { <loop

...s. This is usually a good thing to check before > unrolling, but the compiler’s dependence analysis may be too > conservative in some cases. In addition to tuning the cost model, I found that the vectorizer does not even choose to get that far into its analysis for some loops that I need unrolled. In this particular case, there are three loops that need to be unrolled to get the performance I'm looking for. Of the three, only one gets far enough in the analysis to decide whether we unroll it or not. But I found a bigger issue. The loop optimizers run under the loop pass manager (I...

...5 PM, Friedman, Eli <efriedma at codeaurora.org> wrote: > On 10/12/2016 4:35 PM, Charith Mendis via llvm-dev wrote: > > Hi all, > > Attached herewith is a simple vectorized function with loops performing a > simple shuffle. > > I want all loops (inner and outer) to be unrolled by 2 and as such used > -unroll-count=2 > The inner loops(with k as the induction variable and having constant trip > counts) unroll fully, but the outer loop with (j) fails to unroll. > > The llvm code is also attached with inner loops fully unrolled. > > To inspect further, I...

...gt;>> On 10/12/2016 4:35 PM, Charith Mendis via llvm-dev wrote: >>> >>> Hi all, >>> >>> Attached herewith is a simple vectorized function with loops performing >>> a simple shuffle. >>> >>> I want all loops (inner and outer) to be unrolled by 2 and as such used >>> -unroll-count=2 >>> The inner loops(with k as the induction variable and having constant >>> trip counts) unroll fully, but the outer loop with (j) fails to unroll. >>> >>> The llvm code is also attached with inner loops fully u...

Is it possible to unroll a loop (forcibly if necessary) with llvm (possibly the -loop-unroll pass) a constant number of times. I believe that I read that the -unroll-count=x option was removed, correct? So is there some other way to do this or is this just not possible in llvm? -------------- next part -------------- An HTML attachment was scrubbed... URL:

Hi all, Attached herewith is a simple vectorized function with loops performing a simple shuffle. I want all loops (inner and outer) to be unrolled by 2 and as such used -unroll-count=2 The inner loops(with k as the induction variable and having constant trip counts) unroll fully, but the outer loop with (j) fails to unroll. The llvm code is also attached with inner loops fully unrolled. To inspect further, I added the following to the PassM...

Hi Hal, On 21/11/2012 22:38, Hal Finkel wrote: > ----- Original Message ----- >> From: "Ivan Llopard" <ivanllopard at gmail.com> >> To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> >> Sent: Wednesday, November 21, 2012 10:31:07 AM >> Subject: [LLVMdev] Disable loop unroll pass >> >> Hi, >> >> We've a

Hi all, Partial unrolling and runtime unrolling are enabled by default in aarch64 gcc which is help to get performance better. But these two methods are enabled for only several backends in LLVM which are X86, PowerPC and R600. I don't know the history of these two kinds of unrolling, and why they are not widely used. I also want to know is, for aarch64 backend, is it intentionally to get

Hi, We've a target which has hardware support for zero-overhead loops. Currently, we cannot detect them because the loop unroller is unrolling them before entering into the codegen. Looking at its implementation, it seems that it checks if it is profitable to unroll it or not based on certain parameters. Given that zero cost loops building is based more or less on the same constraints

Hi, Ivan: My $0.02. hasZeroCostLooping() disabling unrolling dose not seem to be appropriate for other architectures, at least the one I worked before. You mentioned: >Currently, we cannot detect them because the loop unroller is >unrolling them before entering into the codegen. Looking at its implementation, >it. Could you please articulate why CG fail to recognize it?

I just wanted to add to Krzysztof's response. I'm not sure if you're referring to the case when a compile-time trip count loop is completely unrolled or for a loop with a run-time trip count, which would be partially unrolled. For Hexagon, if we partially unroll a loop, we'd also like to use our hardware loop instructions. That is, unrolling and hardware loops are complementary. Thanks, -- Brendon -- Qualcomm Innovation Center, Inc is a...

Currently, loop fully unroller shares the same default threshold as loop dynamic unroller and partial unroller. This seems conservative because unlike dynamic/partial unrolling, fully unrolling will not affect LSD/ICache performance. In https://reviews.llvm.org/D28368, I proposed to double the threshold for loop fully unroller. This will change the codegen of several SPECCPU benchmarks: Code

Hi, I found LLVM cannot unroll the loop in the example below, while gcc can. Before I dig more about this issue, is this behavior as designed? bool bar(int i); void foo(int *a, int x, int y) { for (int i = 0; i < 4; ++i) { if (bar(i)) { break; } a[i] = i; } } Btw, if s/break/continue, LLVM is able to unroll it. Thanks, Jingyue -------------- next part --------------

...here but not on the cold path). > > I would even wire the *unrolling* the other way: just suppress unrolling in cold paths to save binary size. rolled loops seem like a generally good thing in cold code unless they are having some larger impact (IE, the loop itself is more expensive than the unrolled form). > > > Agree that we could suppress unrolling in cold path to save code size. But that's orthogonal with the propose here. This proposal focuses on O2 performance: shall we have different (higher) fully unroll threshold than dynamic/partial unroll. I agree that this is (to som...

Hi, I'm interesting in find a pass for loop unrolling in LLVM compiler. I tried opt --loop-unroll --unroll-count=4, but it don't work well. What pass I can used and how? I would also like to know if there is any way to mark the loops that I want them to be unroll Thanks you. -------------- next part -------------- An HTML attachment was scrubbed... URL:

...Which is in line to what I thought. However for this code snippet: if (EnableUnrollAndJam) { // Unroll and Jam. We do this before unroll but need to be in a separate // loop pass manager in order for the outer loop to be processed by // unroll and jam before the inner loop is unrolled. MPM.add(createLoopUnrollAndJamPass(OptLevel)); } MPM.add(createLoopUnrollPass(OptLevel)); // Unroll small loops I see: Loop-Closed SSA Form Pass Loop Pass Manager Unroll and Jam loops Loop Pass Manager Unroll loops Lazy Branch Probability...

Hello, I tried to do some small experiments on the loop unroll transformation. Following is the Test Program. I compiled it as follows: $ opt -loop-rotate -debug-only=loop-unroll -loop-unroll -unroll-count=2 test1.o -S -o test1.s ------------------ int a[1024]; int main() { int i, sum=0; for(i=0; i<1024; ++i) sum += a[i]; printf("%d",sum); } ------------------- I got