search for: tinytripcountvectorthreshold

...f %cmp.zero = icmp eq i32 %0, %n br i1 %cmp.zero, label %middle.block, label %vector.body //================ That is , if n <=7, the program will skip the vector.body. In LoopVectorize.cpp , I see the following code: //================ static cl::opt<unsigned> TinyTripCountVectorThreshold("vectorizer-min-trip-count", cl::init(16), ... ); //================ The minimal loop count is 16. What is the "n<=7" meaning? Thanks. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/atta...

Hi, The TinyTripCountVectorThreshold only applies to loops with a known (constant) trip count. If a loop has a trip count below this value we don’t attempt to vectorize the loop. The loop below has an unknown trip count. Once we decide to vectorize a loop, we emit code to check whether we can execute one iteration of the vectorized b...

...if I should decide to generate vectorized IR directly. (This is in code coming from a DSL which will impliciltly insert annotations, not manually written loops.) Cheers, Dave On Thu, May 23, 2013 at 5:06 AM, Arnold Schwaighofer < aschwaighofer at apple.com> wrote: > Hi, > > The TinyTripCountVectorThreshold only applies to loops with a known > (constant) trip count. If a loop has a trip count below this value we don’t > attempt to vectorize the loop. The loop below has an unknown trip count. > > Once we decide to vectorize a loop, we emit code to check whether we can > execute one itera...

Hi Nadav, Thanks for the response. I forgot to mention that there is an upper limit of 16 for the Trip Count check, TinyTripCountVectorThreshold = 16; if (TC > 0u && TC < TinyTripCountVectorThreshold). So right now, any loop with Trip Count as 0, or with value >=16, LV with unroll. With the change to the lower bound, it will also include the loop with 0 trip count. SCEV returns 0 trip count for this case, because it identi...

...hen you can either use the BB vectorization pass or the SLP vectorization pass to vectorize it. -Hal > Cheers, > Dave > > > > > > On Thu, May 23, 2013 at 5:06 AM, Arnold Schwaighofer < > aschwaighofer at apple.com > wrote: > > > Hi, > > The TinyTripCountVectorThreshold only applies to loops with a known > (constant) trip count. If a loop has a trip count below this value > we don’t attempt to vectorize the loop. The loop below has an > unknown trip count. > > Once we decide to vectorize a loop, we emit code to check whether we > can execute one...

...cur, where this is possible, to make such an effort justifiable? Best, Arnold On Sep 27, 2013, at 12:17 PM, Murali, Sriram <sriram.murali at intel.com> wrote: > Hi Nadav, > Thanks for the response. I forgot to mention that there is an upper limit of 16 for the Trip Count check, > TinyTripCountVectorThreshold = 16; > if (TC > 0u && TC < TinyTripCountVectorThreshold). So right now, any loop with Trip Count as 0, or with value >=16, LV with unroll. With the change to the lower bound, it will also include the loop with 0 trip count. > SCEV returns 0 trip count for this case, because...

...onsecutive within a stride. > > a[0] a[1] a[3] a[4] a[9] a[10] a[11] a[12] > > Not something the loop vectorizer currently understands. >> b) have the loop vectorizer process loops with trip count equal to >> the vector length ? > > You should be able to change "TinyTripCountVectorThreshold" in > loopvectorizer.cpp I managed to set this option when using 'opt' tool. Is there a way to set it when using the API without changing the default value in the source code and recompiling LLVM? >> >> One of both solutions will be needed, I guess. >> >&gt...

Hi Sriram, Thanks for performing this analysis. The problem here, both for memcpy and the vectorizer, is that we can’t predict the size of “n”, even though the only use of ’n’ is for the loop bound for the alloca [4 x [8 x i32]]. If you change the unroll condition to TC >= 0 then you will disable loop unrolling for all loops because getSmallConstantTripCount returns an unsigned number. You

...er because your individual accesses are consecutive within a stride. a[0] a[1] a[3] a[4] a[9] a[10] a[11] a[12] Not something the loop vectorizer currently understands. > b) have the loop vectorizer process loops with trip count equal to the vector length ? You should be able to change "TinyTripCountVectorThreshold" in loopvectorizer.cpp > > One of both solutions will be needed, I guess. > > Frank > > > >> On 05/11/13 22:12, Andrew Trick wrote: >> >>> On Oct 30, 2013, at 11:21 PM, Renato Golin <renato.golin at linaro.org> wrote: >>> >>...

Hi, I am trying to get a small loop to *not vectorize* for cases where it doesn't make sense. For instance, this loop: void foo(int a[4][8], int n) { int b[4][8]; for(int i = 0; i < 4; i++) { for(int j = 0; j < n; j++) { a[i][j] = b[i][j]; } } } * Has maximum of 8ints copy. LLVM tries to use Memcpy for the inner loop. It is not helpful to perform

Good that you bring this up. I still have no solution to this vectorization problem. However, I can rewrite the code and insert a second loop which eliminates the 'urem' and 'div' instructions in the index calculations. In this case, the inner loop's trip count would be equal to the SIMD length and the loop vectorizer ignores the loop. Unrolling the loop and SLP is not an

...e remainder loop. Would be good to leverage any information that can be derived about TC either statically or based on profiling, when determining EpilogVF. Potential speedups and overheads/slowdowns could possibly be demonstrated using extreme cases; what would the best and worst cases be? Perhaps TinyTripCountVectorThreshold is also affected? o Finally, VPlan is currently modeling how to vectorize the loop body according to the potentially profitable VF’s. It’s modelling could be used to generate vector code for both body and remainder, and to consider their combined, overall cost. Ayal. From: llvm-dev [mailto:llvm...

On 02/22/2017 11:52 AM, Adam Nemet via llvm-dev wrote: > Hi Ashutosh, > >> On Feb 22, 2017, at 1:57 AM, Nema, Ashutosh via llvm-dev >> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: >> >> Hi, >> This is a proposal about epilog loop vectorization. >> Currently Loop Vectorizer inserts an epilogue loop for handling loops

...e remainder loop. Would be good to leverage any information that can be derived about TC either statically or based on profiling, when determining EpilogVF. Potential speedups and overheads/slowdowns could possibly be demonstrated using extreme cases; what would the best and worst cases be? Perhaps TinyTripCountVectorThreshold is also affected? >> >> o Finally, VPlan is currently modeling how to vectorize the loop body according to the potentially profitable VF’s. It’s modelling could be used to generate vector code for both body and remainder, and to consider their combined, overall cost. >> >&g...