[PATCH] D24833: [LoopDataPrefetch/AArch64] Allow selective prefetching of symbolic strided accesses

[Renato Golin via llvm-commits]

rengolin added a comment.

In https://reviews.llvm.org/D24833#552654, @bmakam wrote:

> I have included all the gains and regressions in the summary. Only regression I saw on Kryo was a -1.28% in spec2006/h264ref and rest all were solid gains.


Oh, I missed the negative result. :)


================
Comment at: test/Transforms/LoopDataPrefetch/AArch64/kryo-large-stride.ll:7
@@ -4,1 +6,3 @@
 ; RUN: opt -mcpu=kryo -mtriple=aarch64-gnu-linux -passes=loop-data-prefetch -S < %s | FileCheck %s --check-prefix=NO_LARGE_PREFETCH --check-prefix=ALL
+; RUN: opt -mcpu=kryo -mtriple=aarch64-gnu-linux -passes=loop-data-prefetch -S < %s | FileCheck %s --check-prefix=SYMBOLIC_PREFETCH --check-prefix=ALL
+; RUN: opt -mcpu=kryo -mtriple=aarch64-gnu-linux -passes=loop-data-prefetch -prefetch-degree=0 -S < %s | FileCheck %s --check-prefix=NO_SYMBOLIC_PREFETCH --check-prefix=ALL
----------------
bmakam wrote:
> rengolin wrote:
> > Don't force the CPU here, we have the -prefetch-degree for that. Once we have a CPU that pre-fetches aren't profitable, we can use Kryo vs that one as an example, *in addition* to the flag-based ones.
> The LoopDataPrefetch pass is gated by targets that have PrefetchDistance set, so I am forcing the CPU to enable the software prefetcher. The -prefetch-degree flag is to enable the next line prefetching heuristic for targets that set the PrefetchDegree which is only Kryo currently.
Right, makes sense. Thanks!


https://reviews.llvm.org/D24833