[llvm] [AArch64][SVE] Support copy of PPR2 register class in copyPhysReg (PR #216303)

[Sander de Smalen via llvm-commits]

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@@ -5742,36 +5742,36 @@ static const MachineInstrBuilder &AddSubReg(const MachineInstrBuilder &MIB,
 }
 
 static bool forwardCopyWillClobberTuple(unsigned DestReg, unsigned SrcReg,
-                                        unsigned NumRegs) {
-  // We really want the positive remainder mod 32 here, that happens to be
+                                        unsigned NumRegs, bool IsPred) {
+  // We really want the positive remainder mod 16/32 here, that happens to be
   // easily obtainable with a mask.
-  return ((DestReg - SrcReg) & 0x1f) < NumRegs;
+  unsigned MaxRegs = IsPred ? 0xf : 0x1f;
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sdesmalen-arm wrote:

I was hoping we could use something like `getLargestLegalSuperClass`, but maybe that won't work. An alternative way to make this more generic would be to implement a little loop that checks if there's any overlap between any of the registers using `TRI->regsOverlap()`, but that's more compute intensive. So, the current approach is actually fine.

nit: instead of passing `IsPred`, can you pass `unsigned MaxRegs` directly (and also initialise it with `15` or `31` (instead of `0xf` and `0x1f`)
another nit: this function only has a single use, it could just be inlined and named `ForwardCopyWillClobberTuple = ...`

https://github.com/llvm/llvm-project/pull/216303