From 65c15cbd4a555c5fdf4f12ecfbba7a2702087e3f Mon Sep 17 00:00:00 2001
From: "William S. Moses" <gh@wsmoses.com>
Date: Tue, 11 Jan 2022 13:33:43 -0500
Subject: [PATCH] [MLIR][LLVM] Add MemRead/MemWrite behavior to llvm
 store/load/addressof ops

This patch adds corresponding memory effects to mlir llvm-dialect load/store/addressof ops, which thus enables canonicalizations of those ops (like dead code elimination) that rely on the effect interface

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D117041
---
 mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td |  6 +++---
 mlir/test/Dialect/LLVMIR/canonicalize.mlir  | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td b/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
index 328ff9da3639..c6b52c722c2d 100644
--- a/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
+++ b/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
@@ -356,7 +356,7 @@ def LLVM_GEPOp : LLVM_Op<"getelementptr", [NoSideEffect]> {
 }
 
 def LLVM_LoadOp : LLVM_Op<"load">, MemoryOpWithAlignmentAndAttributes {
-  let arguments = (ins LLVM_PointerTo<LLVM_LoadableType>:$addr,
+  let arguments = (ins Arg<LLVM_PointerTo<LLVM_LoadableType>, "", [MemRead]>:$addr,
                    OptionalAttr<SymbolRefArrayAttr>:$access_groups,
                    OptionalAttr<SymbolRefArrayAttr>:$alias_scopes,
                    OptionalAttr<SymbolRefArrayAttr>:$noalias_scopes,
@@ -390,7 +390,7 @@ def LLVM_LoadOp : LLVM_Op<"load">, MemoryOpWithAlignmentAndAttributes {
 
 def LLVM_StoreOp : LLVM_Op<"store">, MemoryOpWithAlignmentAndAttributes {
   let arguments = (ins LLVM_LoadableType:$value,
-                   LLVM_PointerTo<LLVM_LoadableType>:$addr,
+                   Arg<LLVM_PointerTo<LLVM_LoadableType>,"",[MemWrite]>:$addr,
                    OptionalAttr<SymbolRefArrayAttr>:$access_groups,
                    OptionalAttr<SymbolRefArrayAttr>:$alias_scopes,
                    OptionalAttr<SymbolRefArrayAttr>:$noalias_scopes,
@@ -861,7 +861,7 @@ def UnnamedAddr : LLVM_EnumAttr<
   let cppNamespace = "::mlir::LLVM";
 }
 
-def LLVM_AddressOfOp : LLVM_Op<"mlir.addressof"> {
+def LLVM_AddressOfOp : LLVM_Op<"mlir.addressof", [NoSideEffect]> {
   let arguments = (ins FlatSymbolRefAttr:$global_name);
   let results = (outs LLVM_Type:$res);
 
diff --git a/mlir/test/Dialect/LLVMIR/canonicalize.mlir b/mlir/test/Dialect/LLVMIR/canonicalize.mlir
index 7185920efe54..acc08c6453bc 100644
--- a/mlir/test/Dialect/LLVMIR/canonicalize.mlir
+++ b/mlir/test/Dialect/LLVMIR/canonicalize.mlir
@@ -104,3 +104,21 @@ func @llvm_constant() -> i32 {
   // CHECK: return %[[RES]]
   return %2 : i32
 }
+
+// -----
+
+// CHECK-LABEL: load_dce
+// CHECK-NEXT: llvm.return
+llvm.func @load_dce(%x : !llvm.ptr<i8>) {
+  %0 = llvm.load %x : !llvm.ptr<i8>
+  llvm.return 
+}
+
+llvm.mlir.global external @fp() : !llvm.ptr<i8>
+
+// CHECK-LABEL: addr_dce
+// CHECK-NEXT: llvm.return
+llvm.func @addr_dce(%x : !llvm.ptr<i8>) {
+  %0 = llvm.mlir.addressof @fp : !llvm.ptr<ptr<i8>>
+  llvm.return 
+}