[mlir] Add pass to enable Armv9 Streaming SVE mode

This patch adds a pass 'enable-arm-streaming' that enables the Armv9
Scalable Matrix Extension (SME) Streaming SVE (SSVE) mode [1] by adding
either of the following attributes to 'func.func' ops:

  * arm_streaming (default)
  * arm_locally_streaming

PATCH [2 / 2] in series for RFC: https://discourse.llvm.org/t/rfc-supporting-armv9-scalable-matrix-extension-sme-streaming-sve-ssve-mode-in-mlir/70678

[1] https://developer.arm.com/documentation/ddi0616/aa

Reviewed By: awarzynski, dcaballe

Differential Revision: https://reviews.llvm.org/D150934

Author: c-rhodes

mlir/include/mlir/Dialect/ArmSME/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(Transforms)

mlir/include/mlir/Dialect/ArmSME/Transforms/CMakeLists.txt

@@ -0,0 +1,5 @@
+set(LLVM_TARGET_DEFINITIONS Passes.td)
+mlir_tablegen(Passes.h.inc -gen-pass-decls -name ArmSME)
+add_public_tablegen_target(MLIRArmSMETransformsIncGen)
+
+add_mlir_doc(Passes ArmSMEPasses ./ -gen-pass-doc)

mlir/include/mlir/Dialect/ArmSME/Transforms/Passes.h

@@ -0,0 +1,43 @@
+//===- Passes.h - Pass Entrypoints ------------------------------*- 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 MLIR_DIALECT_ARMSME_TRANSFORMS_PASSES_H
+#define MLIR_DIALECT_ARMSME_TRANSFORMS_PASSES_H
+
+#include "mlir/Pass/Pass.h"
+
+namespace mlir {
+
+class RewritePatternSet;
+
+namespace arm_sme {
+// Options for Armv9 Streaming SVE mode. By default, streaming-mode is part of
+// the function interface (ABI) and the caller manages PSTATE.SM on entry/exit.
+// In a locally streaming function PSTATE.SM is kept internal and the callee
+// manages it on entry/exit.
+enum class ArmStreaming { Default = 0, Locally = 1 };
+
+#define GEN_PASS_DECL
+#include "mlir/Dialect/ArmSME/Transforms/Passes.h.inc"
+
+/// Pass to enable Armv9 Streaming SVE mode.
+std::unique_ptr<Pass>
+createEnableArmStreamingPass(const ArmStreaming mode = ArmStreaming::Default);
+
+//===----------------------------------------------------------------------===//
+// Registration
+//===----------------------------------------------------------------------===//
+
+/// Generate the code for registering passes.
+#define GEN_PASS_REGISTRATION
+#include "mlir/Dialect/ArmSME/Transforms/Passes.h.inc"
+
+} // namespace arm_sme
+} // namespace mlir
+
+#endif // MLIR_DIALECT_ARMSME_TRANSFORMS_PASSES_H

mlir/include/mlir/Dialect/ArmSME/Transforms/Passes.td

@@ -0,0 +1,40 @@
+//===-- Passes.td - ArmSME pass definition file ------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_DIALECT_ARMSME_TRANSFORMS_PASSES_TD
+#define MLIR_DIALECT_ARMSME_TRANSFORMS_PASSES_TD
+
+include "mlir/Pass/PassBase.td"
+
+def EnableArmStreaming
+    : Pass<"enable-arm-streaming", "mlir::func::FuncOp"> {
+  let summary = "Enable Armv9 Streaming SVE mode";
+  let description = [{
+    Enables the Armv9 Streaming SVE mode [1] for func.func ops by annotating
+    them with attributes. See options for more details.
+
+    [1] https://developer.arm.com/documentation/ddi0616/aa
+  }];
+  let constructor = "mlir::arm_sme::createEnableArmStreamingPass()";
+  let options = [
+    Option<"mode", "mode", "mlir::arm_sme::ArmStreaming",
+          /*default=*/"mlir::arm_sme::ArmStreaming::Default",
+          "Select how streaming-mode is managed at the function-level.",
+          [{::llvm::cl::values(
+                clEnumValN(mlir::arm_sme::ArmStreaming::Default, "default",
+						   "Streaming mode is part of the function interface "
+						   "(ABI), caller manages PSTATE.SM on entry/exit."),
+                clEnumValN(mlir::arm_sme::ArmStreaming::Locally, "locally",
+						   "Streaming mode is internal to the function, callee "
+						   "manages PSTATE.SM on entry/exit.")
+          )}]>,
+  ];
+  let dependentDialects = ["func::FuncDialect"];
+}
+
+#endif // MLIR_DIALECT_ARMSME_TRANSFORMS_PASSES_TD

mlir/include/mlir/Dialect/CMakeLists.txt

@@ -3,6 +3,7 @@ add_subdirectory(AMX)
 add_subdirectory(Affine)
 add_subdirectory(Arith)
 add_subdirectory(ArmNeon)
+add_subdirectory(ArmSME)
 add_subdirectory(ArmSVE)
 add_subdirectory(Async)
 add_subdirectory(Bufferization)

mlir/include/mlir/InitAllPasses.h

@@ -18,6 +18,7 @@
 #include "mlir/Dialect/AMDGPU/Transforms/Passes.h"
 #include "mlir/Dialect/Affine/Passes.h"
 #include "mlir/Dialect/Arith/Transforms/Passes.h"
+#include "mlir/Dialect/ArmSME/Transforms/Passes.h"
 #include "mlir/Dialect/Async/Passes.h"
 #include "mlir/Dialect/Bufferization/Transforms/Passes.h"
 #include "mlir/Dialect/Func/Transforms/Passes.h"
@@ -77,6 +78,7 @@ inline void registerAllPasses() {
   tosa::registerTosaOptPasses();
   transform::registerTransformPasses();
   vector::registerVectorPasses();
+  arm_sme::registerArmSMEPasses();
 
   // Dialect pipelines
   sparse_tensor::registerSparseTensorPipelines();

mlir/lib/Dialect/ArmSME/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(Transforms)

mlir/lib/Dialect/ArmSME/Transforms/CMakeLists.txt

@@ -0,0 +1,13 @@
+add_mlir_dialect_library(MLIRArmSMETransforms
+  EnableArmStreaming.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/ArmSME/Transforms
+
+  DEPENDS
+  MLIRArmSMETransformsIncGen
+
+  LINK_LIBS PUBLIC
+  MLIRFuncDialect
+  MLIRPass
+  )

mlir/lib/Dialect/ArmSME/Transforms/EnableArmStreaming.cpp

@@ -0,0 +1,75 @@
+//===- EnableArmStreaming.cpp - Enable Armv9 Streaming SVE mode -----------===//
+//
+// 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 pass enables the Armv9 Scalable Matrix Extension (SME) Streaming SVE
+// (SSVE) mode [1][2] by adding either of the following attributes to
+// 'func.func' ops:
+//
+//   * 'arm_streaming' (default)
+//   * 'arm_locally_streaming'
+//
+// Streaming-mode is part of the interface (ABI) for functions with the
+// first attribute and it's the responsibility of the caller to manage
+// PSTATE.SM on entry/exit to functions with this attribute [3]. The LLVM
+// backend will emit 'smstart sm' / 'smstop sm' [4] around calls to
+// streaming functions.
+//
+// In locally streaming functions PSTATE.SM is kept internal and managed by
+// the callee on entry/exit. The LLVM backend will emit 'smstart sm' /
+// 'smstop sm' in the prologue / epilogue for functions with this
+// attribute.
+//
+// [1] https://developer.arm.com/documentation/ddi0616/aa
+// [2] https://llvm.org/docs/AArch64SME.html
+// [3] https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#671pstatesm-interfaces
+// [4] https://developer.arm.com/documentation/ddi0602/2023-03/Base-Instructions/SMSTART--Enables-access-to-Streaming-SVE-mode-and-SME-architectural-state--an-alias-of-MSR--immediate--
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/ArmSME/Transforms/Passes.h"
+
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+
+#define DEBUG_TYPE "enable-arm-streaming"
+
+namespace mlir {
+namespace arm_sme {
+#define GEN_PASS_DEF_ENABLEARMSTREAMING
+#include "mlir/Dialect/ArmSME/Transforms/Passes.h.inc"
+} // namespace arm_sme
+} // namespace mlir
+
+using namespace mlir;
+using namespace mlir::arm_sme;
+
+static constexpr char kArmStreamingAttr[] = "arm_streaming";
+static constexpr char kArmLocallyStreamingAttr[] = "arm_locally_streaming";
+
+namespace {
+struct EnableArmStreamingPass
+    : public arm_sme::impl::EnableArmStreamingBase<EnableArmStreamingPass> {
+  EnableArmStreamingPass(ArmStreaming mode) { this->mode = mode; }
+  void runOnOperation() override {
+    std::string attr;
+    switch (mode) {
+    case ArmStreaming::Default:
+      attr = kArmStreamingAttr;
+      break;
+    case ArmStreaming::Locally:
+      attr = kArmLocallyStreamingAttr;
+      break;
+    }
+    getOperation()->setAttr(attr, UnitAttr::get(&getContext()));
+  }
+};
+} // namespace
+
+std::unique_ptr<Pass>
+mlir::arm_sme::createEnableArmStreamingPass(const ArmStreaming mode) {
+  return std::make_unique<EnableArmStreamingPass>(mode);
+}

mlir/lib/Dialect/CMakeLists.txt

@@ -2,6 +2,7 @@ add_subdirectory(Affine)
 add_subdirectory(AMDGPU)
 add_subdirectory(Arith)
 add_subdirectory(ArmNeon)
+add_subdirectory(ArmSME)
 add_subdirectory(ArmSVE)
 add_subdirectory(Async)
 add_subdirectory(AMX)