[llvm] [AArch64][SVE] Share code across SVE prologue/epilogue implementations (NFCI) (PR #162253)

[Sander de Smalen via llvm-commits]

================
@@ -334,6 +355,55 @@ bool AArch64PrologueEpilogueCommon::shouldCombineCSRLocalStackBump(
   return true;
 }
 
+SVEFrameSizes AArch64PrologueEpilogueCommon::getSVEStackFrameSizes() const {
+  StackOffset PPRCalleeSavesSize =
+      StackOffset::getScalable(AFI->getPPRCalleeSavedStackSize());
+  StackOffset ZPRCalleeSavesSize =
+      StackOffset::getScalable(AFI->getZPRCalleeSavedStackSize());
+  StackOffset PPRLocalsSize = AFL.getPPRStackSize(MF) - PPRCalleeSavesSize;
+  StackOffset ZPRLocalsSize = AFL.getZPRStackSize(MF) - ZPRCalleeSavesSize;
+  if (SVELayout == SVEStackLayout::Split)
+    return {{PPRCalleeSavesSize, PPRLocalsSize},
+            {ZPRCalleeSavesSize, ZPRLocalsSize}};
+  // For simplicity, attribute all locals to ZPRs when split SVE is disabled.
----------------
sdesmalen-arm wrote:

Do we want to add some asserts on the alignment? (e.g. PPRCalleeSavesSize + PPRLocalsSize must be 16-byte aligned. Same for PPRCalleeSaveSize in the case below?

https://github.com/llvm/llvm-project/pull/162253