[llvm] [LV] Consider interleaving & tail-folding when -enable-wide-lane-mask=true (PR #163387)

[David Sherwood via llvm-commits]

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@@ -6146,8 +6154,11 @@ bool AArch64TTIImpl::preferPredicateOverEpilogue(TailFoldingInfo *TFI) const {
   if (Required == TailFoldingOpts::Disabled)
     Required |= TailFoldingOpts::Simple;
 
-  if (!TailFoldingOptionLoc.satisfies(ST->getSVETailFoldingDefaultOpts(),
-                                      Required))
+  TailFoldingOpts DefaultOpts = ST->getSVETailFoldingDefaultOpts();
+  if (TFI->UseWideLaneMask)
+    DefaultOpts |= TailFoldingOpts::Simple;
+
+  if (!TailFoldingOptionLoc.satisfies(DefaultOpts, Required))
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david-arm wrote:

I'm not sure it's a good idea to ignore the instruction threshold below because the problem that exists for normal tail-folding will also exist for wide lane masks. If the user really wants to test the special case of tail-folding for small loops they can always do it in conjunction with -sve-tail-folding-insn-threshold=0.

https://github.com/llvm/llvm-project/pull/163387