diff --git a/flang/include/flang/Optimizer/Analysis/TBAAForest.h b/flang/include/flang/Optimizer/Analysis/TBAAForest.h
index 86030f0be26ae..b69e50bbe05c7 100644
--- a/flang/include/flang/Optimizer/Analysis/TBAAForest.h
+++ b/flang/include/flang/Optimizer/Analysis/TBAAForest.h
@@ -9,9 +9,11 @@
 #ifndef FORTRAN_OPTIMIZER_ANALYSIS_TBAA_FOREST_H
 #define FORTRAN_OPTIMIZER_ANALYSIS_TBAA_FOREST_H
 
+#include "flang/Optimizer/Dialect/FIROpsSupport.h"
 #include "mlir/Dialect/Func/IR/FuncOps.h"
 #include "mlir/Dialect/LLVMIR/LLVMAttrs.h"
 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
+#include "mlir/IR/Attributes.h"
 #include "mlir/IR/MLIRContext.h"
 #include "llvm/ADT/DenseMap.h"
 #include <string>
@@ -82,6 +84,12 @@ class TBAAForrest {
     return getFuncTree(func.getSymNameAttr());
   }
   inline const TBAATree &operator[](mlir::LLVM::LLVMFuncOp func) {
+    // the external name conversion pass may rename some functions. Their old
+    // name must be used so that we add to the tbaa tree added in the FIR pass
+    mlir::Attribute attr = func->getAttr(getInternalFuncNameAttrName());
+    if (attr) {
+      return getFuncTree(attr.cast<mlir::StringAttr>());
+    }
     return getFuncTree(func.getSymNameAttr());
   }
 
diff --git a/flang/include/flang/Optimizer/Dialect/FIROpsSupport.h b/flang/include/flang/Optimizer/Dialect/FIROpsSupport.h
index 00c06d0cbe619..977949e399a53 100644
--- a/flang/include/flang/Optimizer/Dialect/FIROpsSupport.h
+++ b/flang/include/flang/Optimizer/Dialect/FIROpsSupport.h
@@ -93,6 +93,12 @@ static constexpr llvm::StringRef getInternalProcedureAttrName() {
   return "fir.internal_proc";
 }
 
+/// Attribute containing the original name of a function from before the
+/// ExternalNameConverision pass runs
+static constexpr llvm::StringRef getInternalFuncNameAttrName() {
+  return "fir.internal_name";
+}
+
 /// Does the function, \p func, have a host-associations tuple argument?
 /// Some internal procedures may have access to host procedure variables.
 bool hasHostAssociationArgument(mlir::func::FuncOp func);
diff --git a/flang/lib/Optimizer/Transforms/ExternalNameConversion.cpp b/flang/lib/Optimizer/Transforms/ExternalNameConversion.cpp
index e967a8f19d53a..221e93ff85e18 100644
--- a/flang/lib/Optimizer/Transforms/ExternalNameConversion.cpp
+++ b/flang/lib/Optimizer/Transforms/ExternalNameConversion.cpp
@@ -9,11 +9,13 @@
 #include "flang/Common/Fortran.h"
 #include "flang/Optimizer/Dialect/FIRDialect.h"
 #include "flang/Optimizer/Dialect/FIROps.h"
+#include "flang/Optimizer/Dialect/FIROpsSupport.h"
 #include "flang/Optimizer/Support/InternalNames.h"
 #include "flang/Optimizer/Transforms/Passes.h"
 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
 #include "mlir/Dialect/OpenACC/OpenACC.h"
 #include "mlir/Dialect/OpenMP/OpenMPDialect.h"
+#include "mlir/IR/Attributes.h"
 #include "mlir/IR/SymbolTable.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Transforms/DialectConversion.h"
@@ -75,7 +77,8 @@ struct MangleNameOnFuncOp : public mlir::OpRewritePattern<mlir::func::FuncOp> {
                   mlir::PatternRewriter &rewriter) const override {
     mlir::LogicalResult ret = success();
     rewriter.startRootUpdate(op);
-    auto result = fir::NameUniquer::deconstruct(op.getSymName());
+    llvm::StringRef oldName = op.getSymName();
+    auto result = fir::NameUniquer::deconstruct(oldName);
     if (fir::NameUniquer::isExternalFacingUniquedName(result)) {
       auto newSymbol =
           rewriter.getStringAttr(mangleExternalName(result, appendUnderscore));
@@ -86,6 +89,9 @@ struct MangleNameOnFuncOp : public mlir::OpRewritePattern<mlir::func::FuncOp> {
 
       op.setSymNameAttr(newSymbol);
       mlir::SymbolTable::setSymbolName(op, newSymbol);
+
+      op->setAttr(fir::getInternalFuncNameAttrName(),
+                  mlir::StringAttr::get(op->getContext(), oldName));
     }
 
     updateEarlyOutliningParentName(op, appendUnderscore);
diff --git a/flang/test/Fir/external-mangling.fir b/flang/test/Fir/external-mangling.fir
index 5e7cb978838e4..06e1e2e412295 100644
--- a/flang/test/Fir/external-mangling.fir
+++ b/flang/test/Fir/external-mangling.fir
@@ -49,8 +49,8 @@ func.func private @_QPbar2(!fir.ref<f32>)
 
 // LLVMIR-UNDER: llvm.mlir.global common @a_(dense<0> : vector<4xi8>) {{.*}} : !llvm.array<4 x i8>
 // LLVMIR-UNDER: llvm.mlir.global common @__BLNK__(dense<0> : vector<4xi8>) {{.*}}  : !llvm.array<4 x i8>
-// LLVMIR-UNDER: llvm.func @bar_(!llvm.ptr) attributes {sym_visibility = "private"}
-// LLVMIR-UNDER: llvm.func @bar2_(!llvm.ptr) attributes {sym_visibility = "private"}
+// LLVMIR-UNDER: llvm.func @bar_(!llvm.ptr) attributes {fir.internal_name = "_QPbar", sym_visibility = "private"}
+// LLVMIR-UNDER: llvm.func @bar2_(!llvm.ptr) attributes {fir.internal_name = "_QPbar2", sym_visibility = "private"}
 
 // LLVMIR-NOUNDER: %{{.*}} = llvm.mlir.addressof @a : !llvm.ptr
 // LLVMIR-NOUNDER: %{{.*}} = llvm.mlir.addressof @__BLNK__ : !llvm.ptr
@@ -59,8 +59,8 @@ func.func private @_QPbar2(!fir.ref<f32>)
 
 // LLVMIR-NOUNDER: llvm.mlir.global common @a(dense<0> : vector<4xi8>) {{.*}} : !llvm.array<4 x i8>
 // LLVMIR-NOUNDER: llvm.mlir.global common @__BLNK__(dense<0> : vector<4xi8>) {{.*}}  : !llvm.array<4 x i8>
-// LLVMIR-NOUNDER: llvm.func @bar(!llvm.ptr) attributes {sym_visibility = "private"}
-// LLVMIR-NOUNDER: llvm.func @bar2(!llvm.ptr) attributes {sym_visibility = "private"}
+// LLVMIR-NOUNDER: llvm.func @bar(!llvm.ptr) attributes {fir.internal_name = "_QPbar", sym_visibility = "private"}
+// LLVMIR-NOUNDER: llvm.func @bar2(!llvm.ptr) attributes {fir.internal_name = "_QPbar2", sym_visibility = "private"}
 
 // ----- 
 
@@ -96,5 +96,5 @@ func.func @_QPwriteindex_omp_outline_0() attributes {omp.outline_parent_name = "
    return
 }
 
-// CHECK-UNDER: attributes {omp.outline_parent_name = "writeindex_"}
-// CHECK-NOUNDER: attributes {omp.outline_parent_name = "writeindex"}
+// CHECK-UNDER: attributes {fir.internal_name = "_QPwriteindex_omp_outline_0", omp.outline_parent_name = "writeindex_"}
+// CHECK-NOUNDER: attributes {fir.internal_name = "_QPwriteindex_omp_outline_0", omp.outline_parent_name = "writeindex"}