[llvm] CodeGen: Eliminate dynamic relocations in the register superclass tables. (PR #119122)

[Owen Anderson via llvm-commits]

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@@ -172,7 +172,8 @@ X86RegisterInfo::getLargestLegalSuperClass(const TargetRegisterClass *RC,
       if (getRegSizeInBits(*Super) == getRegSizeInBits(*RC))
         return Super;
     }
-    Super = *I++;
+    Super = I.isValid() ? getRegClass(*I) : nullptr;
+    ++I;
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resistor wrote:

In practice it won't break anything here, since the iterator is just a pointer. This whole code path is somewhat awkward, but I don't want to mess with it too much without understanding the underlying logic.

https://github.com/llvm/llvm-project/pull/119122