[llvm] [AArch64][GlobalISel] Implement selectVaStartAAPCS (PR #106979)

[Thorsten Schütt via llvm-commits]

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@@ -1994,7 +1994,108 @@ bool AArch64InstructionSelector::selectVectorAshrLshr(
 
 bool AArch64InstructionSelector::selectVaStartAAPCS(
     MachineInstr &I, MachineFunction &MF, MachineRegisterInfo &MRI) const {
-  return false;
+
+  if (MF.getSubtarget<AArch64Subtarget>().isCallingConvWin64(
+          MF.getFunction().getCallingConv(), MF.getFunction().isVarArg()))
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tschuett wrote:

Sorry. Could you instead copy the SDAG and do the Windows test here:
https://github.com/llvm/llvm-project/blob/350019e8b178394de03ff0cab38375ba806c9dc0/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp#L3564
and add an empty `selectWin64VASTART` function, which returns false.

https://github.com/llvm/llvm-project/pull/106979