[llvm] Add the 'initializes' attribute langref and support (PR #84803)

[Arthur Eubanks via llvm-commits]

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@@ -858,6 +859,14 @@ class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
     }
   }
 
+  Expected<ConstantRange>
+  readBitWidthAndConstantRange(ArrayRef<uint64_t> Record, unsigned &OpNum) {
+    if (Record.size() - OpNum < 3)
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aeubanks wrote:

I'd check `1` instead of `3` and let `readConstantRange` deal with its own reading error

https://github.com/llvm/llvm-project/pull/84803