[llvm] [TableGen][DecoderEmitter] Fix decoder reading bytes past instruction (PR #154916)

[Rahul Joshi via llvm-commits]

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@@ -501,28 +516,47 @@ class FilterChooser {
   };
 
 public:
+  /// Constructs a top-level filter chooser.
   FilterChooser(ArrayRef<InstructionEncoding> Encodings,
-                ArrayRef<unsigned> EncodingIDs, unsigned BW,
+                ArrayRef<unsigned> EncodingIDs, unsigned MaxFilterWidth,
                 const DecoderEmitter *E)
-      : Encodings(Encodings), EncodingIDs(EncodingIDs), FilterBits(BW),
-        Parent(nullptr), BitWidth(BW), Emitter(E) {
+      : Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(nullptr),
+        MaxFilterWidth(MaxFilterWidth), Emitter(E) {
+    // Sort encoding IDs once.
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jurahul wrote:

When my other fix goes in (to set BitWidth = 8 * Size), we won't need to do this sorting for fixed length instructions it seems (since they will all correctly have the same bitwidth unlike today), so this will be needed only for variable length insts. Is that fair to day?

https://github.com/llvm/llvm-project/pull/154916