[mlir][Transforms] More detailed error message when new IR cannot be legalized

Author: matthias-springer

mlir/lib/Transforms/Utils/DialectConversion.cpp

@@ -2302,6 +2302,37 @@ OperationLegalizer::legalizeWithFold(Operation *op,
   return success();
 }
 
+/// Report a fatal error indicating that newly produced or modified IR could
+/// not be legalized.
+static void
+reportNewIrLegalizationFatalError(const Pattern &pattern,
+                                  const SetVector<Operation *> &newOps,
+                                  const SetVector<Operation *> &modifiedOps,
+                                  const SetVector<Block *> &insertedBlocks) {
+  StringRef detachedBlockStr = "(detached block)";
+  std::string newOpNames = llvm::join(
+      llvm::map_range(
+          newOps, [](Operation *op) { return op->getName().getStringRef(); }),
+      ", ");
+  std::string modifiedOpNames = llvm::join(
+      llvm::map_range(
+          newOps, [](Operation *op) { return op->getName().getStringRef(); }),
+      ", ");
+  std::string insertedBlockNames = llvm::join(
+      llvm::map_range(insertedBlocks,
+                      [&](Block *block) {
+                        if (block->getParentOp())
+                          return block->getParentOp()->getName().getStringRef();
+                        return detachedBlockStr;
+                      }),
+      ", ");
+  llvm::report_fatal_error(
+      "pattern '" + pattern.getDebugName() +
+      "' produced IR that could not be legalized. " + "new ops: {" +
+      newOpNames + "}, " + "modified ops: {" + modifiedOpNames + "}, " +
+      "inserted block into ops: {" + insertedBlockNames + "}");
+}
+
 LogicalResult
 OperationLegalizer::legalizeWithPattern(Operation *op,
                                         ConversionPatternRewriter &rewriter) {
@@ -2389,8 +2420,8 @@ OperationLegalizer::legalizeWithPattern(Operation *op,
     appliedPatterns.erase(&pattern);
     if (failed(result)) {
       if (!rewriterImpl.config.allowPatternRollback)
-        llvm::report_fatal_error("pattern '" + pattern.getDebugName() +
-                                 "' produced IR that could not be legalized");
+        reportNewIrLegalizationFatalError(pattern, newOps, modifiedOps,
+                                          insertedBlocks);
       rewriterImpl.resetState(curState, pattern.getDebugName());
     }
     if (config.listener)