[mlir] Print some message for op-printing verification

[Chia-hungDuan]

Summary

Before dump, Insetad of switching to generic form silently after
verification failure. Print some debug logs to help identify why an op
may be printed in a different way.

[Mogball]

mlir/lib/IR/AsmPrinter.cpp

1319–1320

1327–1328

1334–1336

[Chia-hungDuan]

mlir/lib/IR/AsmPrinter.cpp

1319–1320

I may prefer to mention this is run by printer, changed to
"verifying operation before printing: "

[Chia-hungDuan]

Address review comment

[rriddle]

mlir/lib/IR/AsmPrinter.cpp

52

1319–1320

Would likely be nice to just prefix the message with the debug type:

mlir-asm-printer: Verifying operation: ...

[Chia-hungDuan]

Address review comment

[rriddle]

Nice!

mlir/lib/IR/AsmPrinter.cpp

 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/ScopedHashTable.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/TypeSwitch.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/Support/Threading.h"
 
 #include <tuple>
 
 using namespace mlir;
 using namespace mlir::detail;
 
+#define DEBUG_TYPE "asm-printer"
+
 void OperationName::print(raw_ostream &os) const { os << getStringRef(); }
 
 void OperationName::dump() const { print(llvm::errs()); }
 
 //===--------------------------------------------------------------------===//
 // AsmParser
 //===--------------------------------------------------------------------===//
 

 /// fails. We need to do this because custom print functions may fail for
 /// invalid ops.
 static OpPrintingFlags verifyOpAndAdjustFlags(Operation *op,
                                               OpPrintingFlags printerFlags) {
   if (printerFlags.shouldPrintGenericOpForm() ||
       printerFlags.shouldAssumeVerified())
     return printerFlags;
 
+  LLVM_DEBUG(llvm::dbgs() << "Verify op before printing: "
+                          << op->getName().getStringRef() << "\n");
+
   // Ignore errors emitted by the verifier. We check the thread id to avoid
   // consuming other threads' errors.
   auto parentThreadId = llvm::get_threadid();
-  ScopedDiagnosticHandler diagHandler(op->getContext(), [&](Diagnostic &) {
-    return success(parentThreadId == llvm::get_threadid());
+  ScopedDiagnosticHandler diagHandler(op->getContext(), [&](Diagnostic &diag) {
+    if (parentThreadId == llvm::get_threadid()) {
+      LLVM_DEBUG(llvm::dbgs() << "op-printing verification:\n"
+                              << diag.str() << "\n");
+      return success();
+    }
+    return failure();
   });
-  if (failed(verify(op)))
+  if (failed(verify(op))) {
+    LLVM_DEBUG(llvm::dbgs()
+               << op->getName().getStringRef()
+               << " failed on verification, will be printed in generic form\n");
     printerFlags.printGenericOpForm();
+  }
 
   return printerFlags;
 }
 
 AsmState::AsmState(Operation *op, const OpPrintingFlags &printerFlags,
                    LocationMap *locationMap)
     : impl(std::make_unique<AsmStateImpl>(
           op, verifyOpAndAdjustFlags(op, printerFlags), locationMap)) {}