[flang-commits] [flang] [flang] use TBAA Forest in TBAABuilder (PR #68437)

via flang-commits flang-commits at lists.llvm.org
Fri Oct 6 11:21:33 PDT 2023


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-flang-codegen

<details>
<summary>Changes</summary>

See previous reviews at https://github.com/llvm/llvm-project/pull/68414 and https://github.com/llvm/llvm-project/pull/68317

This is important to ensure that tags end up in the same trees that were
created in the FIR TBAA pass. If they are in different trees then
everything in one tree will be assumed to MayAlias with everything in the
other tree. This leads to poor performance.

@<!-- -->vzakhari requested that the old (not-per-function) trees are
maintained so I left the old test intact.

---

Patch is 102.40 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/68437.diff


25 Files Affected:

- (added) flang/include/flang/Optimizer/Analysis/TBAAForest.h (+104) 
- (modified) flang/include/flang/Optimizer/CodeGen/TBAABuilder.h (+15-30) 
- (modified) flang/include/flang/Optimizer/Dialect/CMakeLists.txt (+4) 
- (modified) flang/include/flang/Optimizer/Dialect/FIRDialect.td (+3-1) 
- (modified) flang/include/flang/Optimizer/Dialect/FIROps.h (+1) 
- (modified) flang/include/flang/Optimizer/Dialect/FIROps.td (+12-5) 
- (added) flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.h (+27) 
- (added) flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.td (+59) 
- (modified) flang/include/flang/Optimizer/Transforms/Passes.h (+1) 
- (modified) flang/include/flang/Optimizer/Transforms/Passes.td (+20) 
- (modified) flang/lib/Optimizer/Analysis/CMakeLists.txt (+1) 
- (added) flang/lib/Optimizer/Analysis/TBAAForest.cpp (+60) 
- (modified) flang/lib/Optimizer/CodeGen/CodeGen.cpp (+12-3) 
- (modified) flang/lib/Optimizer/CodeGen/TBAABuilder.cpp (+30-28) 
- (modified) flang/lib/Optimizer/Dialect/CMakeLists.txt (+1) 
- (modified) flang/lib/Optimizer/Dialect/FIRDialect.cpp (+2) 
- (modified) flang/lib/Optimizer/Dialect/FIROps.cpp (+16-1) 
- (added) flang/lib/Optimizer/Dialect/FirAliasAnalysisOpInterface.cpp (+31) 
- (added) flang/lib/Optimizer/Transforms/AddAliasTags.cpp (+198) 
- (modified) flang/lib/Optimizer/Transforms/CMakeLists.txt (+1) 
- (added) flang/test/Fir/tbaa-codegen.fir (+47) 
- (added) flang/test/Fir/tbaa-codegen2.fir (+114) 
- (modified) flang/test/Fir/tbaa.fir (+13-11) 
- (added) flang/test/Transforms/tbaa.fir (+175) 
- (added) flang/test/Transforms/tbaa2.fir (+386) 


``````````diff
diff --git a/flang/include/flang/Optimizer/Analysis/TBAAForest.h b/flang/include/flang/Optimizer/Analysis/TBAAForest.h
new file mode 100644
index 000000000000000..3d11e6112bacce9
--- /dev/null
+++ b/flang/include/flang/Optimizer/Analysis/TBAAForest.h
@@ -0,0 +1,104 @@
+//===-- TBAAForest.h - A TBAA tree for each function -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_OPTIMIZER_ANALYSIS_TBAA_FOREST_H
+#define FORTRAN_OPTIMIZER_ANALYSIS_TBAA_FOREST_H
+
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Dialect/LLVMIR/LLVMAttrs.h"
+#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
+#include "mlir/IR/MLIRContext.h"
+#include "llvm/ADT/DenseMap.h"
+#include <string>
+
+namespace fir {
+
+//===----------------------------------------------------------------------===//
+// TBAATree
+//===----------------------------------------------------------------------===//
+/// Per-function TBAA tree. Each tree contins branches for data (of various
+/// kinds) and descriptor access
+struct TBAATree {
+  //===----------------------------------------------------------------------===//
+  // TBAAForrest::TBAATree::SubtreeState
+  //===----------------------------------------------------------------------===//
+  /// This contains a TBAA subtree based on some parent. New tags can be added
+  /// under the parent using getTag.
+  class SubtreeState {
+    friend TBAATree; // only allow construction by TBAATree
+  public:
+    SubtreeState() = delete;
+    SubtreeState(const SubtreeState &) = delete;
+    SubtreeState(SubtreeState &&) = default;
+
+    mlir::LLVM::TBAATagAttr getTag(llvm::StringRef uniqueId) const;
+
+  private:
+    SubtreeState(mlir::MLIRContext *ctx, std::string name,
+                 mlir::LLVM::TBAANodeAttr grandParent)
+        : parentId{std::move(name)}, context(ctx) {
+      parent = mlir::LLVM::TBAATypeDescriptorAttr::get(
+          context, parentId, mlir::LLVM::TBAAMemberAttr::get(grandParent, 0));
+    }
+
+    const std::string parentId;
+    mlir::MLIRContext *const context;
+    mlir::LLVM::TBAATypeDescriptorAttr parent;
+    llvm::DenseMap<llvm::StringRef, mlir::LLVM::TBAATagAttr> tagDedup;
+  };
+
+  SubtreeState globalDataTree;
+  SubtreeState allocatedDataTree;
+  SubtreeState dummyArgDataTree;
+  mlir::LLVM::TBAATypeDescriptorAttr anyAccessDesc;
+  mlir::LLVM::TBAATypeDescriptorAttr boxMemberTypeDesc;
+  mlir::LLVM::TBAATypeDescriptorAttr anyDataTypeDesc;
+
+  static TBAATree buildTree(mlir::StringAttr functionName);
+
+private:
+  TBAATree(mlir::LLVM::TBAATypeDescriptorAttr anyAccess,
+           mlir::LLVM::TBAATypeDescriptorAttr dataRoot,
+           mlir::LLVM::TBAATypeDescriptorAttr boxMemberTypeDesc);
+};
+
+//===----------------------------------------------------------------------===//
+// TBAAForrest
+//===----------------------------------------------------------------------===//
+/// Colletion of TBAATrees, usually indexed by function (so that each function
+/// has a different TBAATree)
+class TBAAForrest {
+public:
+  explicit TBAAForrest(bool separatePerFunction = true)
+      : separatePerFunction{separatePerFunction} {}
+
+  inline const TBAATree &operator[](mlir::func::FuncOp func) {
+    return getFuncTree(func.getSymNameAttr());
+  }
+  inline const TBAATree &operator[](mlir::LLVM::LLVMFuncOp func) {
+    return getFuncTree(func.getSymNameAttr());
+  }
+
+private:
+  const TBAATree &getFuncTree(mlir::StringAttr symName) {
+    if (!separatePerFunction)
+      symName = mlir::StringAttr::get(symName.getContext(), "");
+    if (!trees.contains(symName))
+      trees.insert({symName, TBAATree::buildTree(symName)});
+    return trees.at(symName);
+  }
+
+  // Should each function use a different tree?
+  const bool separatePerFunction;
+  // TBAA tree per function
+  llvm::DenseMap<mlir::StringAttr, TBAATree> trees;
+};
+
+} // namespace fir
+
+#endif // FORTRAN_OPTIMIZER_ANALYSIS_TBAA_FOREST_H
diff --git a/flang/include/flang/Optimizer/CodeGen/TBAABuilder.h b/flang/include/flang/Optimizer/CodeGen/TBAABuilder.h
index 3aeb124f911867e..2c5795678a91e16 100644
--- a/flang/include/flang/Optimizer/CodeGen/TBAABuilder.h
+++ b/flang/include/flang/Optimizer/CodeGen/TBAABuilder.h
@@ -13,8 +13,8 @@
 #ifndef FORTRAN_OPTIMIZER_CODEGEN_TBAABUILDER_H
 #define FORTRAN_OPTIMIZER_CODEGEN_TBAABUILDER_H
 
+#include "flang/Optimizer/Analysis/TBAAForest.h"
 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
-#include "mlir/IR/BuiltinAttributes.h"
 
 namespace fir {
 
@@ -25,9 +25,9 @@ namespace fir {
 //
 // TBAA type information is represented with LLVM::MetadataOp operation
 // with specific symbol name `TBAABuilder::tbaaMetaOpName`. The basic
-// TBAA tree used for Flang consists of the following nodes:
+// TBAA trees used for Flang consists of the following nodes:
 //   llvm.metadata @__flang_tbaa {
-//     llvm.tbaa_root @root_0 {id = "Flang Type TBAA Root"}
+//     llvm.tbaa_root @root_0 {id = "Flang Type TBAA Function Root funcName"}
 //     llvm.tbaa_type_desc @type_desc_1 {id = "any access",
 //                                       members = {<@root_0, 0>}}
 //     llvm.tbaa_type_desc @type_desc_2 {id = "any data access",
@@ -162,6 +162,9 @@ namespace fir {
 // Given the storage association, all non-box accesses are represented
 // with the conservative data access tag:
 //   < `<any data access>`, `<any data access>`, 0 >
+
+// additional tags are added in flang/Optimizer/Transforms/AddAliasTags.cpp
+// (before CodeGen)
 class TBAABuilder {
 public:
   TBAABuilder(mlir::MLIRContext *context, bool applyTBAA);
@@ -184,13 +187,13 @@ class TBAABuilder {
 
   // Returns TBAATagAttr representing access tag:
   //   < <descriptor member>, <descriptor member>, 0 >
-  mlir::LLVM::TBAATagAttr getAnyBoxAccessTag();
+  mlir::LLVM::TBAATagAttr getAnyBoxAccessTag(mlir::LLVM::LLVMFuncOp func);
   // Returns TBAATagAttr representing access tag:
   //   < <any data access>, <any data access>, 0 >
-  mlir::LLVM::TBAATagAttr getAnyDataAccessTag();
+  mlir::LLVM::TBAATagAttr getAnyDataAccessTag(mlir::LLVM::LLVMFuncOp func);
   // Returns TBAATagAttr representing access tag:
   //   < <any access>, <any access>, 0 >
-  mlir::LLVM::TBAATagAttr getAnyAccessTag();
+  mlir::LLVM::TBAATagAttr getAnyAccessTag(mlir::LLVM::LLVMFuncOp func);
 
   // Returns TBAATagAttr representing access tag described by the base and
   // access FIR types and the LLVM::GepOp representing the access in terms of
@@ -198,7 +201,8 @@ class TBAABuilder {
   // fir::BaseBoxType.
   mlir::LLVM::TBAATagAttr getBoxAccessTag(mlir::Type baseFIRType,
                                           mlir::Type accessFIRType,
-                                          mlir::LLVM::GEPOp gep);
+                                          mlir::LLVM::GEPOp gep,
+                                          mlir::LLVM::LLVMFuncOp func);
 
   // Returns TBAATagAttr representing access tag described by the base and
   // access FIR types and the LLVM::GepOp representing the access in terms of
@@ -206,34 +210,13 @@ class TBAABuilder {
   // "data" access, i.e. not an access of any box/descriptor member.
   mlir::LLVM::TBAATagAttr getDataAccessTag(mlir::Type baseFIRType,
                                            mlir::Type accessFIRType,
-                                           mlir::LLVM::GEPOp gep);
+                                           mlir::LLVM::GEPOp gep,
+                                           mlir::LLVM::LLVMFuncOp func);
 
   // Set to true, if TBAA builder is active, otherwise, all public
   // methods are no-ops.
   bool enableTBAA;
 
-  // LLVM::TBAARootAttr identifying Flang's TBAA root.
-  mlir::LLVM::TBAARootAttr flangTBAARoot;
-  // Identity string for Flang's TBAA root.
-  static constexpr llvm::StringRef flangTBAARootId = "Flang Type TBAA Root";
-
-  // LLVM::TBAATypeDescriptorAttr identifying "any access".
-  mlir::LLVM::TBAATypeDescriptorAttr anyAccessTypeDesc;
-  // Identity string for "any access" type descriptor.
-  static constexpr llvm::StringRef anyAccessTypeDescId = "any access";
-
-  // LLVM::TBAATypeDescriptorAttr identifying "any data access" (i.e. non-box
-  // memory access).
-  mlir::LLVM::TBAATypeDescriptorAttr anyDataAccessTypeDesc;
-  // Identity string for "any data access" type descriptor.
-  static constexpr llvm::StringRef anyDataAccessTypeDescId = "any data access";
-
-  // LLVM::TBAATypeDescriptorAttr identifying "descriptor member" access, i.e.
-  // any access within the bounds of a box/descriptor.
-  mlir::LLVM::TBAATypeDescriptorAttr boxMemberTypeDesc;
-  // Identity string for "descriptor member" type descriptor.
-  static constexpr llvm::StringRef boxMemberTypeDescId = "descriptor member";
-
   // Number of attached TBAA tags (used for debugging).
   unsigned tagAttachmentCounter = 0;
 
@@ -247,6 +230,8 @@ class TBAABuilder {
       std::tuple<mlir::LLVM::TBAANodeAttr, mlir::LLVM::TBAANodeAttr, int64_t>,
       mlir::LLVM::TBAATagAttr>
       tagsMap;
+
+  TBAAForrest trees;
 };
 
 } // namespace fir
diff --git a/flang/include/flang/Optimizer/Dialect/CMakeLists.txt b/flang/include/flang/Optimizer/Dialect/CMakeLists.txt
index d657e3f16690377..15c835aad9bc7d2 100644
--- a/flang/include/flang/Optimizer/Dialect/CMakeLists.txt
+++ b/flang/include/flang/Optimizer/Dialect/CMakeLists.txt
@@ -18,6 +18,10 @@ set(LLVM_TARGET_DEFINITIONS FortranVariableInterface.td)
 mlir_tablegen(FortranVariableInterface.h.inc -gen-op-interface-decls)
 mlir_tablegen(FortranVariableInterface.cpp.inc -gen-op-interface-defs)
 
+set(LLVM_TARGET_DEFINITIONS FirAliasAnalysisOpInterface.td)
+mlir_tablegen(FirAliasAnalaysOpInterface.h.inc -gen-op-interface-decls)
+mlir_tablegen(FirAliasAnalysisOpInterface.cpp.inc -gen-op-interface-defs)
+
 set(LLVM_TARGET_DEFINITIONS CanonicalizationPatterns.td)
 mlir_tablegen(CanonicalizationPatterns.inc -gen-rewriters)
 add_public_tablegen_target(CanonicalizationPatternsIncGen)
diff --git a/flang/include/flang/Optimizer/Dialect/FIRDialect.td b/flang/include/flang/Optimizer/Dialect/FIRDialect.td
index d0735bbeb2d3d88..b366b6d40e4e213 100644
--- a/flang/include/flang/Optimizer/Dialect/FIRDialect.td
+++ b/flang/include/flang/Optimizer/Dialect/FIRDialect.td
@@ -30,7 +30,9 @@ def fir_Dialect : Dialect {
   let dependentDialects = [
     // Arith dialect provides FastMathFlagsAttr
     // supported by some FIR operations.
-    "arith::ArithDialect"
+    "arith::ArithDialect",
+    // TBAA Tag types
+    "LLVM::LLVMDialect"
   ];
 }
 
diff --git a/flang/include/flang/Optimizer/Dialect/FIROps.h b/flang/include/flang/Optimizer/Dialect/FIROps.h
index 8f03dc5cf795225..bab35bac5c81f4b 100644
--- a/flang/include/flang/Optimizer/Dialect/FIROps.h
+++ b/flang/include/flang/Optimizer/Dialect/FIROps.h
@@ -11,6 +11,7 @@
 
 #include "flang/Optimizer/Dialect/FIRAttr.h"
 #include "flang/Optimizer/Dialect/FIRType.h"
+#include "flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.h"
 #include "flang/Optimizer/Dialect/FortranVariableInterface.h"
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Dialect/Func/IR/FuncOps.h"
diff --git a/flang/include/flang/Optimizer/Dialect/FIROps.td b/flang/include/flang/Optimizer/Dialect/FIROps.td
index a57add9f731979d..fae9b92662f3559 100644
--- a/flang/include/flang/Optimizer/Dialect/FIROps.td
+++ b/flang/include/flang/Optimizer/Dialect/FIROps.td
@@ -16,10 +16,12 @@
 
 include "mlir/Dialect/Arith/IR/ArithBase.td"
 include "mlir/Dialect/Arith/IR/ArithOpsInterfaces.td"
+include "mlir/Dialect/LLVMIR/LLVMAttrDefs.td"
 include "flang/Optimizer/Dialect/FIRDialect.td"
 include "flang/Optimizer/Dialect/FIRTypes.td"
 include "flang/Optimizer/Dialect/FIRAttr.td"
 include "flang/Optimizer/Dialect/FortranVariableInterface.td"
+include "flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.td"
 include "mlir/IR/BuiltinAttributes.td"
 
 // Base class for FIR operations.
@@ -258,7 +260,7 @@ def fir_FreeMemOp : fir_Op<"freemem", [MemoryEffects<[MemFree]>]> {
   let assemblyFormat = "$heapref attr-dict `:` qualified(type($heapref))";
 }
 
-def fir_LoadOp : fir_OneResultOp<"load", []> {
+def fir_LoadOp : fir_OneResultOp<"load", [FirAliasAnalysisOpInterface]> {
   let summary = "load a value from a memory reference";
   let description = [{
     Load a value from a memory reference into an ssa-value (virtual register).
@@ -274,9 +276,11 @@ def fir_LoadOp : fir_OneResultOp<"load", []> {
     or null.
   }];
 
-  let arguments = (ins Arg<AnyReferenceLike, "", [MemRead]>:$memref);
+  let arguments = (ins Arg<AnyReferenceLike, "", [MemRead]>:$memref,
+                  OptionalAttr<LLVM_TBAATagArrayAttr>:$tbaa);
 
-  let builders = [OpBuilder<(ins "mlir::Value":$refVal)>];
+  let builders = [OpBuilder<(ins "mlir::Value":$refVal)>,
+                  OpBuilder<(ins "mlir::Type":$resTy, "mlir::Value":$refVal)>];
 
   let hasCustomAssemblyFormat = 1;
 
@@ -285,7 +289,7 @@ def fir_LoadOp : fir_OneResultOp<"load", []> {
   }];
 }
 
-def fir_StoreOp : fir_Op<"store", []> {
+def fir_StoreOp : fir_Op<"store", [FirAliasAnalysisOpInterface]> {
   let summary = "store an SSA-value to a memory location";
 
   let description = [{
@@ -305,7 +309,10 @@ def fir_StoreOp : fir_Op<"store", []> {
   }];
 
   let arguments = (ins AnyType:$value,
-                   Arg<AnyReferenceLike, "", [MemWrite]>:$memref);
+                   Arg<AnyReferenceLike, "", [MemWrite]>:$memref,
+                   OptionalAttr<LLVM_TBAATagArrayAttr>:$tbaa);
+
+  let builders = [OpBuilder<(ins "mlir::Value":$value, "mlir::Value":$memref)>];
 
   let hasCustomAssemblyFormat = 1;
   let hasVerifier = 1;
diff --git a/flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.h b/flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.h
new file mode 100644
index 000000000000000..c07bf648eab454a
--- /dev/null
+++ b/flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.h
@@ -0,0 +1,27 @@
+//===- FirAliasAnalysisInterface.h ------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains an interface for adding alias analysis information to
+// loads and stores
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_OPTIMIZER_DIALECT_FIR_ALIAS_ANALYSIS_INTERFACE_H
+#define FORTRAN_OPTIMIZER_DIALECT_FIR_ALIAS_ANALYSIS_INTERFACE_H
+
+#include "mlir/IR/OpDefinition.h"
+#include "mlir/IR/Operation.h"
+#include "mlir/Support/LogicalResult.h"
+
+namespace fir::detail {
+mlir::LogicalResult verifyFirAliasAnalysisOpInterface(mlir::Operation *op);
+} // namespace fir::detail
+
+#include "flang/Optimizer/Dialect/FirAliasAnalaysOpInterface.h.inc"
+
+#endif // FORTRAN_OPTIMIZER_DIALECT_FIR_ALIAS_ANALYSIS_INTERFACE_H
diff --git a/flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.td b/flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.td
new file mode 100644
index 000000000000000..1d3e49d383f63a4
--- /dev/null
+++ b/flang/include/flang/Optimizer/Dialect/FirAliasAnalysisOpInterface.td
@@ -0,0 +1,59 @@
+//===-- FirAliasAnalysisOpInterface.td ---------------------*- tablegen -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+include "mlir/IR/Interfaces.td"
+
+def FirAliasAnalysisOpInterface : OpInterface<"FirAliasAnalysisOpInterface"> {
+  let description = [{
+    An interface for memory operations that can carry alias analysis metadata.
+    It provides setters and getters for the operation's alias analysis
+    attributes. The default implementations of the interface methods expect
+    the operation to have an attribute of type ArrayAttr named tbaa.
+    Unlike the mlir::LLVM::AliasAnalysisOpInterface, this only supports tbaa.
+  }];
+
+  let cppNamespace = "::fir";
+  let verify = [{ return detail::verifyFirAliasAnalysisOpInterface($_op); }];
+
+  let methods = [
+    InterfaceMethod<
+      /*desc=*/        "Returns the tbaa attribute or nullptr",
+      /*returnType=*/  "mlir::ArrayAttr",
+      /*methodName=*/  "getTBAATagsOrNull",
+      /*args=*/        (ins),
+      /*methodBody=*/  [{}],
+      /*defaultImpl=*/ [{
+        auto op = mlir::cast<ConcreteOp>(this->getOperation());
+        return op.getTbaaAttr();
+      }]
+      >,
+    InterfaceMethod<
+      /*desc=*/        "Sets the tbaa attribute",
+      /*returnType=*/  "void",
+      /*methodName=*/  "setTBAATags",
+      /*args=*/        (ins "const mlir::ArrayAttr":$attr),
+      /*methodBody=*/  [{}],
+      /*defaultImpl=*/ [{
+        auto op = mlir::cast<ConcreteOp>(this->getOperation());
+        op.setTbaaAttr(attr);
+      }]
+      >,
+    InterfaceMethod<
+      /*desc=*/        "Returns a list of all pointer operands accessed by the "
+                       "operation",
+      /*returnType=*/  "::llvm::SmallVector<::mlir::Value>",
+      /*methodName=*/  "getAccessedOperands",
+      /*args=*/        (ins),
+      /*methodBody=*/  [{}],
+      /*defaultImpl=*/ [{
+        auto op = mlir::cast<ConcreteOp>(this->getOperation());
+        return {op.getMemref()};
+      }]
+      >
+  ];
+}
diff --git a/flang/include/flang/Optimizer/Transforms/Passes.h b/flang/include/flang/Optimizer/Transforms/Passes.h
index 64882c8ec406b0a..30d97be3800c191 100644
--- a/flang/include/flang/Optimizer/Transforms/Passes.h
+++ b/flang/include/flang/Optimizer/Transforms/Passes.h
@@ -61,6 +61,7 @@ std::unique_ptr<mlir::Pass> createMemDataFlowOptPass();
 std::unique_ptr<mlir::Pass> createPromoteToAffinePass();
 std::unique_ptr<mlir::Pass> createMemoryAllocationPass();
 std::unique_ptr<mlir::Pass> createStackArraysPass();
+std::unique_ptr<mlir::Pass> createAliasTagsPass();
 std::unique_ptr<mlir::Pass> createSimplifyIntrinsicsPass();
 std::unique_ptr<mlir::Pass> createAddDebugFoundationPass();
 std::unique_ptr<mlir::Pass> createLoopVersioningPass();
diff --git a/flang/include/flang/Optimizer/Transforms/Passes.td b/flang/include/flang/Optimizer/Transforms/Passes.td
index 80da485392007fa..7aa08b0616de99d 100644
--- a/flang/include/flang/Optimizer/Transforms/Passes.td
+++ b/flang/include/flang/Optimizer/Transforms/Passes.td
@@ -252,6 +252,26 @@ def StackArrays : Pass<"stack-arrays", "mlir::ModuleOp"> {
   let constructor = "::fir::createStackArraysPass()";
 }
 
+def AddAliasTags : Pass<"fir-alias-analysis", "mlir::ModuleOp"> {
+  let summary = "Add tbaa tags to operations that implement FirAliasAnalysisOpInterface";
+  let description = [{
+    TBAA (type based alias analysis) is one method to pass pointer alias information
+    from language frontends to LLVM. This pass uses fir::AliasAnalysis to add this
+    information to fir.load and fir.store operations.
+    Additional tags are added during codegen. See fir::TBAABuilder.
+    This needs to be a separate pass so that it happens before structured control
+    flow operations are lowered to branches and basic blocks (this makes tracing
+    the source of values much eaiser). The other TBAA tags need to be applied to
+    box loads and stores which are implicit in FIR and so cannot be annotated
+    until codegen.
+    TODO: this is currently a pass on mlir::ModuleOp to avoid parallelism. In
+    theory, each operation could be considered in prallel, so long as there
+    aren't races adding new tags to the mlir context.
+  }];
+  let dependentDialects = [ "fir::FIROpsDialect" ];
+  let constructor = "::fir::createAliasTagsPass()";
+}
+
 def SimplifyRegionLite : Pass<"simplify-region-lite", "mlir::ModuleOp"> {
   let summary = "Region simplification";
   let description = [{
diff --git a/flang/lib/Optimizer/Analysis/CMakeLists.txt b/flang/lib/Optimizer/Analysis/CMakeLists.txt
index 19dadf72cf4ce14..436d4d3f18969c1 100644
--- a/flang/lib/Optimizer/Analysis/CMakeLists.txt
+++ b/flang/lib/Optimizer/Analysis/...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/68437


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