[PATCH] D89048: [ARM][LowOverheadLoops] Insert loop start at end of block in more cases

[Sam Parker via Phabricator via llvm-commits]

samparker added a comment.

Sorry, I didn't realise this had been updated.



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Comment at: llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp:1083
+    if (FirstNonTerminator != MBB->end()) {
+        if (RDA.hasSameReachingDef(Start, &*FirstNonTerminator, CountReg) &&
+                   RDA.hasSameReachingDef(Start, &*FirstNonTerminator, ARM::LR))
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I seem to remember being concerned that though we've already chosen an InsertPt, we then compare reaching defs against Start instead... In the case where InsertPt != Start, it means there's a mov lr, after Start and so RDA.isReachingDefLiveOut(Start, ARM::LR) shouldn't be true and RDA.hasSameReachingDef(Start, &*FirstNonTerminator, ARM::LR) may also not be true. Would you mind making another patch to compare against InsertPt and then rebase this on top of that?


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Comment at: llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp:1092
+        auto LastMI = &*MBB->getLastNonDebugInstr();
+        if (RDA.hasSameReachingDef(LastMI, &*InsertPt, CountReg)) {
+            for (auto &Op : InsertPt->operands()) {
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nit: your indentations are too wide.


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  https://reviews.llvm.org/D89048/new/

https://reviews.llvm.org/D89048