[Codegen][Tuner] solve name conflicts for merging td specs (iree-org#22409)

**Follow-up fix for:** iree-org#20127  
**Fixes:** iree-org#20673,
nod-ai/amd-shark-ai#2440

This issue was discovered while tuning BOO, where the same naming
conflict pattern caused the pass to fail.

## Problem

When a module contains both a conflicting name and a suffixed variant of
that name, the pass could create duplicate names during conflict
resolution.

### Example
```mlir
module {  // First module
  @apply_op_config
}
module {  // Second module
  @apply_op_config        // conflicts → would rename to @apply_op_config_0
  @apply_op_config_0      // but this already exists! → BUG
}
```

The second module's `@apply_op_config` would be renamed to
`@apply_op_config_0`, but that name already exists in the same module,
creating a duplicate.

## Solution

This PR checks the newly generated name against `seenNames` and
increments the numeric suffix until finding a unique name:
- `@apply_op_config` → `@apply_op_config_1` (skipping `_0` since it
exists)

The fix uses a simple numeric suffix scheme (e.g., `_0`, `_1`, `_2`)
instead of module prefixes for cleaner and more maintainable code.

---------

Signed-off-by: Bangtian Liu <[email protected]>

Author: bangtianliu

compiler/plugins/target/ROCM/test/default_tuning_specs_amdgpu.mlir

@@ -75,7 +75,7 @@
 // MERGE:         transform.foreach_match
 // MERGE:           @match_mmt -> @apply_op_config,
 // MERGE-NEXT:      @match_attention_2x10x4096x64x64x64_f16 -> @apply_attn_op_config,
-// MERGE-NEXT:      @match_mmt_2048x1280x5120_f16_f16_f32 -> @iree_default_tuning_spec_gfx942_1_apply_op_config
+// MERGE-NEXT:      @match_mmt_2048x1280x5120_f16_f16_f32 -> @apply_op_config_0
 
 // NOTE: The order matters above because `foreach_match` ops performs matching from top to bottom.
 

compiler/src/iree/compiler/Codegen/Common/LinkTuningSpecsPass.cpp

@@ -143,38 +143,22 @@ static TuningSpecsToMerge collectTuningSpecsToMerge(ModuleOp module) {
 }
 
 // Renames a `NamedSequenceOp` to resolve name conflicts caused by merging
-// tuning specs.
-// The name conflict resolution strategy follows below two rules:
-//   1. If the `NamedSequenceOp` is inside a module with a valid symbol name,
-//      its new name is prefixed with its containing module's symbol name.
-//   2. If the module has no symbol name, an incrementing counter is used
-//      to generate a unique prefix (e.g., `m0_`, `m1_`, etc.).
+// tuning specs by appending a numeric suffix until a unique name is found.
 static void updateNamedSequenceOp(
     NamedSequenceOp op, OpBuilder &builder,
     llvm::DenseMap<NamedSequenceOp, ForeachMatchOp> &namedSequenceToUser,
-    llvm::DenseMap<ModuleOp, std::string> &unnamedModuleNames,
-    unsigned &unnamedModuleCounter) {
+    llvm::DenseSet<StringRef> &seenNames) {
   StringRef specName = op.getSymName();
-  ModuleOp parentModule = op->getParentOfType<ModuleOp>();
-  assert(parentModule);
-  StringAttr parentSymbol = parentModule.getSymNameAttr();
-  std::string moduleName;
-  if (parentSymbol) {
-    moduleName = parentSymbol.getValue().str();
-  } else {
-    if (unnamedModuleNames.contains(parentModule)) {
-      moduleName = unnamedModuleNames[parentModule];
-    } else {
-      std::string newModuleName =
-          llvm::formatv("m{}", unnamedModuleCounter).str();
-      ++unnamedModuleCounter;
-      unnamedModuleNames[parentModule] = newModuleName;
-      moduleName = newModuleName;
-    }
+
+  // Ensure the name is unique by appending a numeric suffix if needed.
+  std::string uniqueNewSpecName = specName.str();
+  for (unsigned suffix = 0; seenNames.contains(uniqueNewSpecName); ++suffix) {
+    uniqueNewSpecName = llvm::formatv("{}_{}", specName, suffix).str();
   }
 
-  std::string newSpecName = llvm::formatv("{}_{}", moduleName, specName).str();
-  op.setSymName(newSpecName);
+  op.setSymName(uniqueNewSpecName);
+  StringRef newSeqName = op.getSymName();
+  seenNames.insert(newSeqName);
 
   // Skip updating ForeachMatchOp if the NamedSequenceOp is not used in it.
   if (!namedSequenceToUser.contains(op))
@@ -187,7 +171,7 @@ static void updateNamedSequenceOp(
   auto getUpdatedSymbol = [&](Attribute attr) -> SymbolRefAttr {
     StringRef name = cast<SymbolRefAttr>(attr).getRootReference();
     return (name == specName)
-               ? SymbolRefAttr::get(builder.getContext(), newSpecName)
+               ? SymbolRefAttr::get(builder.getContext(), newSeqName)
                : cast<SymbolRefAttr>(attr);
   };
 
@@ -236,13 +220,8 @@ static LogicalResult resolveAndMoveNamedSequenceOps(
   }
 
   // Update conflicted named sequence ops.
-  if (!nameConflictOps.empty()) {
-    llvm::DenseMap<ModuleOp, std::string> unnamedModuleNames;
-    unsigned unnamedModuleCounter = 0;
-    for (NamedSequenceOp op : nameConflictOps) {
-      updateNamedSequenceOp(op, builder, namedSequenceToUser,
-                            unnamedModuleNames, unnamedModuleCounter);
-    }
+  for (NamedSequenceOp op : nameConflictOps) {
+    updateNamedSequenceOp(op, builder, namedSequenceToUser, seenNames);
   }
 
   // Move all named sequence ops to the top-level module.

compiler/src/iree/compiler/Codegen/Common/test/link_tuning_specs.mlir

@@ -268,8 +268,8 @@ module @td_module attributes { transform.with_named_sequence } {
 // CHECK:         @__kernel_config(
 // CHECK:         transform.foreach_match
 // CHECK:           @match -> @apply_op_config
-// CHECK:           @inner_module_b_match -> @inner_module_b_apply_op_config
-// CHECK:           @inner_module_c_match -> @apply_op_config_1
+// CHECK:           @match_0 -> @apply_op_config_0
+// CHECK:           @match_1 -> @apply_op_config_1
 
 // -----
 
@@ -338,5 +338,56 @@ module @td_module attributes { transform.with_named_sequence } {
 // CHECK:         @__kernel_config(
 // CHECK:         transform.foreach_match
 // CHECK:           @match -> @apply_op_config
-// CHECK:           @m0_match -> @m0_apply_op_config
-// CHECK:           @m1_match -> @apply_op_config_1
+// CHECK:           @match_0 -> @apply_op_config_0
+// CHECK:           @match_1 -> @apply_op_config_1
+
+// -----
+
+// Test secondary conflict: when @apply_op_config from the second module conflicts
+// and would be renamed to @apply_op_config_0, but @apply_op_config_0 already
+// exists in the same module, it should skip to @apply_op_config_1.
+
+module @td_module_secondary_name_conflict attributes {transform.with_named_sequence} {
+  module attributes {iree_codegen.tuning_spec_with_default_entrypoint, transform.with_named_sequence} {
+    transform.named_sequence @apply_op_config(%arg0: !transform.any_op {transform.readonly}) {
+      transform.yield
+    }
+    transform.named_sequence @match_a(%arg0: !transform.any_op {transform.readonly}) -> (!transform.any_op) {
+      transform.yield %arg0 : !transform.any_op
+    }
+    transform.named_sequence @__kernel_config(%arg0: !transform.any_op {transform.consumed}) -> !transform.any_op
+        attributes {iree_codegen.tuning_spec_entrypoint} {
+      %updated_root = transform.foreach_match in %arg0
+          @match_a -> @apply_op_config : (!transform.any_op) -> !transform.any_op
+      transform.yield %updated_root : !transform.any_op
+    }
+  }
+  module attributes {iree_codegen.tuning_spec_with_default_entrypoint, transform.with_named_sequence} {
+    transform.named_sequence @apply_op_config(%arg0: !transform.any_op {transform.readonly}) {
+      transform.yield
+    }
+    transform.named_sequence @apply_op_config_0(%arg0: !transform.any_op {transform.readonly}) {
+      transform.yield
+    }
+    transform.named_sequence @match_b(%arg0: !transform.any_op {transform.readonly}) -> (!transform.any_op) {
+      transform.yield %arg0 : !transform.any_op
+    }
+    transform.named_sequence @match_c(%arg0: !transform.any_op {transform.readonly}) -> (!transform.any_op) {
+      transform.yield %arg0 : !transform.any_op
+    }
+    transform.named_sequence @__kernel_config(%arg0: !transform.any_op {transform.consumed}) -> !transform.any_op
+        attributes {iree_codegen.tuning_spec_entrypoint} {
+      %updated_root = transform.foreach_match in %arg0
+          @match_b -> @apply_op_config,
+          @match_c -> @apply_op_config_0 : (!transform.any_op) -> !transform.any_op
+      transform.yield %updated_root : !transform.any_op
+    }
+  }
+}
+
+// CHECK-LABEL:   module @td_module_secondary_name_conflict
+// CHECK:         @__kernel_config(
+// CHECK:         transform.foreach_match
+// CHECK:           @match_a -> @apply_op_config
+// CHECK:           @match_b -> @apply_op_config_1
+// CHECK:           @match_c -> @apply_op_config_0