[PATCH] D34963: [AArch64][Falkor] Avoid HW prefetcher tag collisions (step 1)

[Matthias Braun via Phabricator via llvm-commits]

MatzeB added inline comments.


================
Comment at: llvm/trunk/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp:9-13
+// For Falkor, we want to avoid HW prefetcher instruction tag collisions that
+// may inhibit the HW prefetching.  This is done in two steps.  Before ISel, we
+// mark strided loads (i.e. those that will likely benefit from prefetching)
+// with metadata.  Then, after opcodes have been finalized, we insert MOVs and
+// re-write loads to prevent unintnentional tag collisions.
----------------
Start with `/// \file` to have doxygen pick it up.


================
Comment at: llvm/trunk/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp:67-69
+    // FIXME: For some reason, preserving SE here breaks LSR (even if
+    // this pass changes nothing).
+    // AU.addPreserved<ScalarEvolutionWrapperPass>();
----------------
how strange...


================
Comment at: llvm/trunk/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp:110
+  for (Loop *I : LI)
+    for (auto L = df_begin(I), LE = df_end(I); L != LE; ++L)
+      MadeChange |= runOnLoop(*L);
----------------
no need for `auto`


================
Comment at: llvm/trunk/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp:116
+
+bool FalkorMarkStridedAccesses::runOnLoop(Loop *L) {
+  // Only mark strided loads in the inner-most loop
----------------
Could use a reference parameter as it cannot be nullptr.


================
Comment at: llvm/trunk/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp:123-124
+
+  for (const auto BB : L->blocks()) {
+    for (auto &I : *BB) {
+      LoadInst *LoadI = dyn_cast<LoadInst>(&I);
----------------
Would be nicer without `auto`.


Repository:
  rL LLVM

https://reviews.llvm.org/D34963