[Mlir-commits] [mlir] [MLIR][LLVM] Allow importing of nameless globals (PR #101918)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-mlir-llvm

@llvm/pr-subscribers-mlir

Author: Ivan R. Ivanov (ivanradanov)

<details>
<summary>Changes</summary>

LLVM allows nameless globals for private global variables whereas in MLIR globals must be addressed using symbols. We attach symbols to nameless globals in order to enable their import.

---
Full diff: https://github.com/llvm/llvm-project/pull/101918.diff


3 Files Affected:

- (modified) mlir/include/mlir/Target/LLVMIR/ModuleImport.h (+3) 
- (modified) mlir/lib/Target/LLVMIR/ModuleImport.cpp (+19-2) 
- (modified) mlir/test/Target/LLVMIR/Import/global-variables.ll (+14-1) 


``````````diff
diff --git a/mlir/include/mlir/Target/LLVMIR/ModuleImport.h b/mlir/include/mlir/Target/LLVMIR/ModuleImport.h
index 04d098d38155b..2667530963109 100644
--- a/mlir/include/mlir/Target/LLVMIR/ModuleImport.h
+++ b/mlir/include/mlir/Target/LLVMIR/ModuleImport.h
@@ -19,6 +19,7 @@
 #include "mlir/Target/LLVMIR/Import.h"
 #include "mlir/Target/LLVMIR/LLVMImportInterface.h"
 #include "mlir/Target/LLVMIR/TypeFromLLVM.h"
+#include "llvm/IR/GlobalVariable.h"
 
 namespace llvm {
 class BasicBlock;
@@ -367,6 +368,8 @@ class ModuleImport {
   ModuleOp mlirModule;
   /// The LLVM module being imported.
   std::unique_ptr<llvm::Module> llvmModule;
+  /// Nameless globals
+  DenseMap<llvm::GlobalVariable *, FlatSymbolRefAttr> namelessGlobals;
 
   /// A dialect interface collection used for dispatching the import to specific
   /// dialects.
diff --git a/mlir/lib/Target/LLVMIR/ModuleImport.cpp b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
index 8b40b7b2df6c7..f84ad30a546ea 100644
--- a/mlir/lib/Target/LLVMIR/ModuleImport.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Target/LLVMIR/ModuleImport.h"
+#include "mlir/IR/BuiltinAttributes.h"
 #include "mlir/Target/LLVMIR/Import.h"
 
 #include "AttrKindDetail.h"
@@ -73,6 +74,11 @@ static constexpr StringRef getGlobalCtorsVarName() {
   return "llvm.global_ctors";
 }
 
+/// Prefix used for symbols of nameless llvm globals.
+static constexpr StringRef getNamelessGlobalPrefix() {
+  return "mlir.llvm.nameless_global.";
+}
+
 /// Returns the name of the global_dtors global variables.
 static constexpr StringRef getGlobalDtorsVarName() {
   return "llvm.global_dtors";
@@ -884,9 +890,15 @@ LogicalResult ModuleImport::convertGlobal(llvm::GlobalVariable *globalVar) {
     globalExpressionAttr =
         debugImporter->translateGlobalVariableExpression(globalExpressions[0]);
 
+  std::string globalName = globalVar->getName().str();
+  if (globalName == "") {
+    globalName = getNamelessGlobalPrefix().str() +
+                 std::to_string(namelessGlobals.size());
+    namelessGlobals[globalVar] = FlatSymbolRefAttr::get(context, globalName);
+  }
   GlobalOp globalOp = builder.create<GlobalOp>(
       mlirModule.getLoc(), type, globalVar->isConstant(),
-      convertLinkageFromLLVM(globalVar->getLinkage()), globalVar->getName(),
+      convertLinkageFromLLVM(globalVar->getLinkage()), globalName.c_str(),
       valueAttr, alignment, /*addr_space=*/globalVar->getAddressSpace(),
       /*dso_local=*/globalVar->isDSOLocal(),
       /*thread_local=*/globalVar->isThreadLocal(), /*comdat=*/SymbolRefAttr(),
@@ -1061,7 +1073,12 @@ FailureOr<Value> ModuleImport::convertConstant(llvm::Constant *constant) {
   // Convert global variable accesses.
   if (auto *globalVar = dyn_cast<llvm::GlobalVariable>(constant)) {
     Type type = convertType(globalVar->getType());
-    auto symbolRef = FlatSymbolRefAttr::get(context, globalVar->getName());
+    StringRef globalName = globalVar->getName();
+    FlatSymbolRefAttr symbolRef;
+    if (globalName == "")
+      symbolRef = namelessGlobals[globalVar];
+    else
+      symbolRef = FlatSymbolRefAttr::get(context, globalName);
     return builder.create<AddressOfOp>(loc, type, symbolRef).getResult();
   }
 
diff --git a/mlir/test/Target/LLVMIR/Import/global-variables.ll b/mlir/test/Target/LLVMIR/Import/global-variables.ll
index 902f77bd7e6cb..d8c33e311c626 100644
--- a/mlir/test/Target/LLVMIR/Import/global-variables.ll
+++ b/mlir/test/Target/LLVMIR/Import/global-variables.ll
@@ -280,7 +280,20 @@ define void @bar() {
 ; CHECK-DAG: #[[GLOBAL_VAR:.*]] = #llvm.di_global_variable<file = #[[FILE]], line = 268, type = #[[COMPOSITE_TYPE]], isLocalToUnit = true, isDefined = true>
 ; CHECK-DAG: #[[GLOBAL_VAR_EXPR:.*]] = #llvm.di_global_variable_expression<var = #[[GLOBAL_VAR]], expr = <>>
 
-; CHECK-DAG: llvm.mlir.global external constant @".str.1"() {addr_space = 0 : i32, dbg_expr = #[[GLOBAL_VAR_EXPR]]}
+; CHECK:  llvm.mlir.global private unnamed_addr constant @mlir.llvm.nameless_global.0("0\00") {addr_space = 0 : i32, dso_local}
+; CHECK:  llvm.mlir.global private unnamed_addr constant @mlir.llvm.nameless_global.1("1\00") {addr_space = 0 : i32, dso_local}
+;
+; CHECK:  llvm.mlir.global internal constant @zero() {addr_space = 0 : i32, dso_local} : !llvm.ptr {
+; CHECK:    llvm.mlir.addressof @mlir.llvm.nameless_global.0 : !llvm.ptr
+; CHECK:  llvm.mlir.global internal constant @one() {addr_space = 0 : i32, dso_local} : !llvm.ptr {
+; CHECK:    llvm.mlir.addressof @mlir.llvm.nameless_global.1 : !llvm.ptr
+
+; CHECK: llvm.mlir.global external constant @".str.1"() {addr_space = 0 : i32, dbg_expr = #[[GLOBAL_VAR_EXPR]]}
+
+ at 0 = private unnamed_addr constant [2 x i8] c"0\00"
+ at 1 = private unnamed_addr constant [2 x i8] c"1\00"
+ at zero = internal constant ptr @0
+ at one = internal constant ptr @1
 
 @.str.1 = external constant [10 x i8], !dbg !0
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/101918