[llvm-exegesis] Ignore instructions using custom inserter

[qiucf]

Summary

Some instructions defined in table-gen files sets usesCustomInserter bit, which means it has to be lowered by target code and isn't actually valid instruction at MC level. So we should treat them like pseudo instructions.

[gchatelet]

LGTM thx @qiucf

llvm/test/tools/llvm-exegesis/PowerPC/unsupported-opcode.s

+# RUN: llvm-exegesis -mode=latency -opcode-name=SELECT_I8 2>&1 | FileCheck %s
+
+CHECK: Unsupported opcode: isPseudo/usesCustomInserter

llvm/tools/llvm-exegesis/lib/SerialSnippetGenerator.cpp

computeAliasingInstructions(const LLVMState &State, const Instruction *Instr,
 
   std::vector<const Instruction *> AliasingInstructions;
   for (const unsigned OtherOpcode : Opcodes) {
     if (OtherOpcode == Instr->Description.getOpcode())
       continue;
     const Instruction &OtherInstr = State.getIC().getInstr(OtherOpcode);
     const MCInstrDesc &OtherInstrDesc = OtherInstr.Description;
     // Ignore instructions that we cannot run.
-    if (OtherInstrDesc.isPseudo() ||
+    if (OtherInstrDesc.isPseudo() || OtherInstrDesc.usesCustomInsertionHook() ||
         OtherInstrDesc.isBranch() || OtherInstrDesc.isIndirectBranch() ||
         OtherInstrDesc.isCall() || OtherInstrDesc.isReturn()) {
           continue;
     }
     if (OtherInstr.hasMemoryOperands())
       continue;
     if (!State.getExegesisTarget().allowAsBackToBack(OtherInstr))
       continue;

llvm/tools/llvm-exegesis/llvm-exegesis.cpp

 
 // Generates code snippets for opcode `Opcode`.
 static Expected<std::vector<BenchmarkCode>>
 generateSnippets(const LLVMState &State, unsigned Opcode,
                  const BitVector &ForbiddenRegs) {
   const Instruction &Instr = State.getIC().getInstr(Opcode);
   const MCInstrDesc &InstrDesc = Instr.Description;
   // Ignore instructions that we cannot run.
-  if (InstrDesc.isPseudo())
-    return make_error<Failure>("Unsupported opcode: isPseudo");
+  if (InstrDesc.isPseudo() || InstrDesc.usesCustomInsertionHook())
+    return make_error<Failure>(
+        "Unsupported opcode: isPseudo/usesCustomInserter");
   if (InstrDesc.isBranch() || InstrDesc.isIndirectBranch())
     return make_error<Failure>("Unsupported opcode: isBranch/isIndirectBranch");
   if (InstrDesc.isCall() || InstrDesc.isReturn())
     return make_error<Failure>("Unsupported opcode: isCall/isReturn");
 
   const std::vector<InstructionTemplate> InstructionVariants =
       State.getExegesisTarget().generateInstructionVariants(
           Instr, MaxConfigsPerOpcode);