[llvm] [LLVM][MC] Add support to cull inactive decoders in decoder emitter (PR #154865)

[Rahul Joshi via llvm-commits]

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@@ -2528,45 +2535,80 @@ namespace {
 )";
 
   // Do extra bookkeeping for variable-length encodings.
-  std::vector<unsigned> InstrLen;
   bool IsVarLenInst = Target.hasVariableLengthEncodings();
   unsigned MaxInstLen = 0;
   if (IsVarLenInst) {
-    InstrLen.resize(Target.getInstructions().size(), 0);
+    std::vector<unsigned> InstrLen(Target.getInstructions().size(), 0);
     for (const InstructionEncoding &Encoding : Encodings) {
       MaxInstLen = std::max(MaxInstLen, Encoding.getBitWidth());
       InstrLen[Target.getInstrIntValue(Encoding.getInstruction()->TheDef)] =
           Encoding.getBitWidth();
     }
+
+    // For variable instruction, we emit a instruction length table to let the
+    // decoder know how long the instructions are. You can see example usage in
+    // M68k's disassembler.
+    emitInstrLenTable(OS, InstrLen);
   }
 
-  // Map of (namespace, hwmode, size) tuple to encoding IDs.
-  std::map<std::tuple<StringRef, unsigned, unsigned>, std::vector<unsigned>>
+  // Map of (bitwidth, namespace, hwmode) tuple to encoding IDs.
+  std::map<std::tuple<unsigned, StringRef, unsigned>, std::vector<unsigned>>
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jurahul wrote:

Done,

https://github.com/llvm/llvm-project/pull/154865