[llvm] [NFC][CodeGen] Add helper function to check SubReg validity (PR #181489)

[Rahul Joshi via llvm-commits]

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@@ -442,6 +442,37 @@ const TargetRegisterClass *TargetRegisterInfo::findCommonRegClass(
   return getCommonSubClass(DefRC, SrcRC);
 }
 
+bool TargetRegisterInfo::isSubRegValidForRegClass(const TargetRegisterClass *RC,
+                                                  unsigned Idx) const {
+  // NoSubRegister is always valid.
+  if (!Idx)
+    return true;
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jurahul wrote:

Done.

https://github.com/llvm/llvm-project/pull/181489