[llvm-branch-commits] [mlir] [MLIR][LLVM] Preserve unknown function metadata on import (PR #203022)

[Akimasa Watanuki via llvm-branch-commits]

https://github.com/Men-cotton updated https://github.com/llvm/llvm-project/pull/203022

>From 07c0f68ed5b40d9fc1790176df8513c0ae5f78db Mon Sep 17 00:00:00 2001
From: mencotton <mencotton0410 at gmail.com>
Date: Mon, 8 Jun 2026 20:54:24 +0900
Subject: [PATCH] [MLIR][LLVM] Preserve unknown function metadata on import

Import non-debug function metadata without a kind-specific dialect conversion into LLVMFuncOp function_metadata. Preserve repeated metadata kinds through the generic carrier so LLVM IR import and export can round-trip those attachments.
---
 mlir/lib/Target/LLVMIR/ModuleImport.cpp       | 41 +++++++-
 .../Target/LLVMIR/Import/function-metadata.ll | 95 +++++++++++++++++++
 2 files changed, 131 insertions(+), 5 deletions(-)
 create mode 100644 mlir/test/Target/LLVMIR/Import/function-metadata.ll

diff --git a/mlir/lib/Target/LLVMIR/ModuleImport.cpp b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
index def83537df2f8..c1151b1d02603 100644
--- a/mlir/lib/Target/LLVMIR/ModuleImport.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
@@ -3283,18 +3283,49 @@ LogicalResult ModuleImport::processFunction(llvm::Function *func) {
   // Handle Function attributes.
   processFunctionAttributes(func, funcOp);
 
-  // Convert non-debug metadata by using the dialect interface.
+  // Convert non-debug metadata by using the dialect interface. Metadata without
+  // a kind-specific dialect conversion is preserved in the generic function
+  // metadata carrier.
   SmallVector<std::pair<unsigned, llvm::MDNode *>> allMetadata;
   func->getAllMetadata(allMetadata);
+  SmallVector<StringRef> metadataNames;
+  llvmModule->getMDKindNames(metadataNames);
+  SmallVector<Attribute> functionMetadata;
   for (auto &[kind, node] : allMetadata) {
-    if (!iface.isConvertibleMetadata(kind))
+    if (kind == llvm::LLVMContext::MD_dbg)
       continue;
-    if (failed(iface.setMetadataAttrs(builder, kind, node, funcOp, *this))) {
+
+    llvm::MDNode *metadataNode = node;
+    auto emitUnhandledFunctionMetadataWarning = [&]() {
       emitWarning(funcOp.getLoc())
-          << "unhandled function metadata: " << diagMD(node, llvmModule.get())
-          << " on " << diag(*func);
+          << "unhandled function metadata: "
+          << diagMD(metadataNode, llvmModule.get()) << " on " << diag(*func);
+    };
+
+    if (!iface.isConvertibleMetadata(kind)) {
+      auto getNamelessGlobalSymbol =
+          [this](llvm::GlobalVariable *globalVar) -> FlatSymbolRefAttr {
+        return getOrCreateNamelessSymbolName(globalVar);
+      };
+      Attribute nodeAttr = convertMetadataToAttr(context, metadataNode, iface,
+                                                 getNamelessGlobalSymbol);
+      auto mdNodeAttr = dyn_cast_if_present<LLVM::MDNodeAttr>(nodeAttr);
+      if (!mdNodeAttr || kind >= metadataNames.size()) {
+        emitUnhandledFunctionMetadataWarning();
+        continue;
+      }
+
+      functionMetadata.push_back(LLVM::FunctionMetadataAttr::get(
+          context, builder.getStringAttr(metadataNames[kind]), mdNodeAttr));
+      continue;
     }
+
+    if (failed(
+            iface.setMetadataAttrs(builder, kind, metadataNode, funcOp, *this)))
+      emitUnhandledFunctionMetadataWarning();
   }
+  if (!functionMetadata.empty())
+    funcOp.setFunctionMetadataAttr(builder.getArrayAttr(functionMetadata));
 
   if (func->isDeclaration())
     return success();
diff --git a/mlir/test/Target/LLVMIR/Import/function-metadata.ll b/mlir/test/Target/LLVMIR/Import/function-metadata.ll
new file mode 100644
index 0000000000000..15cf1835974a8
--- /dev/null
+++ b/mlir/test/Target/LLVMIR/Import/function-metadata.ll
@@ -0,0 +1,95 @@
+; RUN: mlir-translate -import-llvm -split-input-file %s | FileCheck %s
+
+; CHECK-LABEL: llvm.func @repeated_type_metadata
+; CHECK-SAME: function_metadata
+; CHECK-SAME: #llvm.func_metadata<"type", <#llvm.md_const<0 : i64>, #llvm.md_string<"typeid0">>>
+; CHECK-SAME: #llvm.func_metadata<"type", <#llvm.md_const<0 : i64>, #llvm.md_string<"typeid1">>>
+define void @repeated_type_metadata() !type !0 !type !1 {
+  ret void
+}
+
+!0 = !{i64 0, !"typeid0"}
+!1 = !{i64 0, !"typeid1"}
+
+; // -----
+
+; CHECK-LABEL: llvm.func @declaration_metadata
+; CHECK-SAME: function_metadata
+; CHECK-SAME: #llvm.func_metadata<"annotation", <#llvm.md_string<"declaration annotation">>>
+declare !annotation !0 void @declaration_metadata()
+
+!0 = !{!"declaration annotation"}
+
+; // -----
+
+declare void @callee()
+
+; CHECK-LABEL: llvm.func @function_ref_metadata
+; CHECK-SAME: function_metadata
+; CHECK-SAME: #llvm.func_metadata<"callees", <#llvm.md_value<@callee>>>
+define void @function_ref_metadata() !callees !0 {
+  ret void
+}
+
+!0 = !{ptr @callee}
+
+; // -----
+
+define void @alias_target() {
+  ret void
+}
+ at alias = alias void (), ptr @alias_target
+
+; CHECK-LABEL: llvm.func @alias_ref_metadata
+; CHECK-SAME: function_metadata
+; CHECK-SAME: #llvm.func_metadata<"callees", <#llvm.md_value<@alias>>>
+define void @alias_ref_metadata() !callees !0 {
+  ret void
+}
+
+!0 = !{ptr @alias}
+
+; // -----
+
+ at global = global i32 0
+
+; CHECK-LABEL: llvm.func @global_ref_metadata
+; CHECK-SAME: function_metadata
+; CHECK-SAME: #llvm.func_metadata<"callees", <#llvm.md_value<@global>>>
+define void @global_ref_metadata() !callees !0 {
+  ret void
+}
+
+!0 = !{ptr @global}
+
+; // -----
+
+ at 0 = global i32 0
+
+; CHECK-LABEL: llvm.func @nameless_global_ref_metadata
+; CHECK-SAME: function_metadata
+; CHECK-SAME: #llvm.func_metadata<"callees", <#llvm.md_value<@{{mlir\.llvm\.nameless_global_[0-9]+}}>>>
+define void @nameless_global_ref_metadata() !callees !0 {
+  ret void
+}
+
+!0 = !{ptr @0}
+
+; // -----
+
+ at ifunc = ifunc void (), ptr @ifunc_resolver
+define ptr @ifunc_resolver() {
+  ret ptr @ifunc_target
+}
+define void @ifunc_target() {
+  ret void
+}
+
+; CHECK-LABEL: llvm.func @ifunc_ref_metadata
+; CHECK-SAME: function_metadata
+; CHECK-SAME: #llvm.func_metadata<"callees", <#llvm.md_value<@ifunc>>>
+define void @ifunc_ref_metadata() !callees !0 {
+  ret void
+}
+
+!0 = !{ptr @ifunc}