[llvm] [ARM] Verify that disassembled instruction is correct (PR #157360)

[Sergei Barannikov via llvm-commits]

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@@ -6103,9 +6076,23 @@ DecodeStatus ARMDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                              ArrayRef<uint8_t> Bytes,
                                              uint64_t Address,
                                              raw_ostream &CS) const {
+  DecodeStatus S;
   if (STI.hasFeature(ARM::ModeThumb))
-    return getThumbInstruction(MI, Size, Bytes, Address, CS);
-  return getARMInstruction(MI, Size, Bytes, Address, CS);
+    S = getThumbInstruction(MI, Size, Bytes, Address, CS);
+  else
+    S = getARMInstruction(MI, Size, Bytes, Address, CS);
+  if (S == DecodeStatus::Fail)
+    return S;
+
+  // Verify that the decoded instruction has the correct number of operands.
+  const MCInstrDesc &MCID = MCII->get(MI.getOpcode());
+  if (!MCID.isVariadic() && MI.getNumOperands() != MCID.getNumOperands()) {
+    reportFatalInternalError(MCII->getName(MI.getOpcode()) + ": expected " +
+                             Twine(MCID.getNumOperands()) + " operands, got " +
+                             Twine(MI.getNumOperands()) + "\n");
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s-barannikov wrote:

Not sure if this should be a fatal error. Maybe report an error and continue? In case there are bugs not detected by tests.

https://github.com/llvm/llvm-project/pull/157360