[llvm] [AArch64] Add a fast-path for AArch64InstrInfo::getInstSizeInBytes (NFC) (PR #221894)

[Alexis Engelke via llvm-commits]

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@@ -204,6 +204,10 @@ static std::optional<unsigned> getLFIInstSizeInBytes(const MachineInstr &MI) {
 /// GetInstSize - Return the number of bytes of code the specified
 /// instruction may be.  This returns the maximum number of bytes.
 unsigned AArch64InstrInfo::getInstSizeInBytes(const MachineInstr &MI) const {
+  const MCInstrDesc &Desc = MI.getDesc();
+  if (!Desc.isPseudo() && !Subtarget.isLFI())
+    return 4;
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aengelke wrote:

Is Desc.getSize() used elsewhere or is the tablegen entry in EncodedI now unused? Maybe assert that getSize() == 4 if the ISA ever changes?

https://github.com/llvm/llvm-project/pull/221894