[mlir:Inliner] Emit an error when adding multiple simplification pipelines for the same op

[rriddle]

Summary

This perculates the incorrect configuration up to the user, instead of being implicit.

Depends on D122880

mlir/lib/Transforms/Inliner.cpp

defaultPipeline = [=](OpPassManager &pm) {
       (void)parsePassPipeline(defaultPipelineCopy, pm);
     };
   } else if (defaultPipelineStr.getNumOccurrences()) {
     defaultPipeline = nullptr;
   }
 
   // Initialize the op specific pass pipelines.
   llvm::StringMap<OpPassManager> pipelines;
-  for (OpPassManager pipeline : opPipelineList)
-    if (!pipeline.empty())
-      pipelines.try_emplace(pipeline.getOpName(), pipeline);
+  for (OpPassManager pipeline : opPipelineList) {
+    if (pipeline.empty())
+      continue;
+    auto it = pipelines.try_emplace(pipeline.getOpName(), pipeline);
+    if (!it.second) {
+      llvm::errs()
+          << "Inliner: Registering duplicate simplification pipeline for op '"
+          << it.first->getKey() << "'\n";
+      return failure();
+    }
+  }
   opPipelines.assign({std::move(pipelines)});
 
   return success();
 }
 
 std::unique_ptr<Pass> mlir::createInlinerPass() {
   return std::make_unique<InlinerPass>();
 }

mlir/test/Transforms/inlining.mlir

 // RUN: mlir-opt %s -inline='default-pipeline=''' | FileCheck %s
 // RUN: mlir-opt %s --mlir-disable-threading -inline='default-pipeline=''' | FileCheck %s
 // RUN: mlir-opt %s -inline='default-pipeline=''' -mlir-print-debuginfo -mlir-print-local-scope | FileCheck %s --check-prefix INLINE-LOC
 // RUN: mlir-opt %s -inline | FileCheck %s --check-prefix INLINE_SIMPLIFY
 // RUN: mlir-opt %s -inline='op-pipelines=func.func(canonicalize,cse)' | FileCheck %s --check-prefix INLINE_SIMPLIFY
+// RUN: not mlir-opt %s -inline='op-pipelines=func.func(canonicalize),func.func(cse)' 2>&1 | FileCheck %s --check-prefix ERROR_DUPLICATE_PIPELINE
+
+// ERROR_DUPLICATE_PIPELINE: Inliner: Registering duplicate simplification pipeline for op 'func.func'
 
 // Inline a function that takes an argument.
 func @func_with_arg(%c : i32) -> i32 {
   %b = arith.addi %c, %c : i32
   return %b : i32
 }
 
 // CHECK-LABEL: func @inline_with_arg