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

[Adam Nemet via llvm-commits]

anemet requested changes to this revision.
This revision now requires changes to proceed.

================
Comment at: lib/Target/AArch64/AArch64Subtarget.cpp:74-75
@@ -73,3 +73,4 @@
     PrefetchDistance = 740;
+    PrefetchDegree = 1;
     MinPrefetchStride = 1024;
     MaxPrefetchIterationsAhead = 11;
----------------
So you are saying on one hand (MinPrefetchStride = 1024) that we shouldn't bother prefetching unless the stride is at least 1K but then you say (PrefetchDegree = 1) that you want to prefetch the very next cache line anytime the stride is not known at compile time.

I feel that there is a contradiction here.  The former suggest that you have a pretty powerful HW prefetcher, the latter that you don't and willing to speculate aggressively to compensate for it.

It seems that something is wrong with the model here.


https://reviews.llvm.org/D24833