[AArch64][LoopVectorize] Enable tail-folding on neoverse-v2

This patch enables tail-folding of simple loops by default when
targeting the neoverse-v2 CPU. This was done for neoverse-v1 in
c7dbe32.

For SPEC2017 with "-Ofast -mcpu=neoverse-v2 -flto" this gives some small
wins:

549.fotonik3d_r: ~3.2%
     525.x264_r: ~2.7%
     554.roms_r: ~1.2%

Author: c-rhodes

llvm/lib/Target/AArch64/AArch64Subtarget.cpp

@@ -268,6 +268,8 @@ void AArch64Subtarget::initializeProperties(bool HasMinSize) {
     MaxBytesForLoopAlignment = 16;
     break;
   case NeoverseV2:
+    DefaultSVETFOpts = TailFoldingOpts::Simple;
+    LLVM_FALLTHROUGH;
   case NeoverseV3:
     EpilogueVectorizationMinVF = 8;
     MaxInterleaveFactor = 4;

llvm/test/Transforms/LoopVectorize/AArch64/sve-tail-folding-option.ll

@@ -11,6 +11,8 @@
 ; RUN: opt < %s -passes=loop-vectorize -sve-tail-folding-insn-threshold=0 -S -sve-tail-folding=default -mcpu=neoverse-v1 | FileCheck %s -check-prefix=CHECK-NEOVERSE-V1
 ; RUN: opt < %s -passes=loop-vectorize -sve-tail-folding-insn-threshold=0 -S -mcpu=neoverse-v1 -sve-tail-folding=default | FileCheck %s -check-prefix=CHECK-NEOVERSE-V1
 ; RUN: opt < %s -passes=loop-vectorize -sve-tail-folding-insn-threshold=0 -S -mcpu=neoverse-v1 | FileCheck %s -check-prefix=CHECK-NEOVERSE-V1
+; Simple tail-folding is also enabled by default on neoverse-v2. Use same check prefix.
+; RUN: opt < %s -passes=loop-vectorize -sve-tail-folding-insn-threshold=0 -S -mcpu=neoverse-v2 | FileCheck %s -check-prefix=CHECK-NEOVERSE-V1
 
 target triple = "aarch64-unknown-linux-gnu"