[llvm-branch-commits] [llvm] [LoongArch] Add memory barrier optimization pass (PR #218597)

[via llvm-branch-commits]

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+//===---- LoongArchMemoryBarrierOpt.cpp - Memory barrier Optimization -----===//
+//
+// 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 removes or merges redundant memory barrier instructions.
+///
+/// - DBAR x + DBAR y -> DBAR (x & y)
+/// - DBAR x + AMO_DB -> AMO_DB
+/// - DBAR x + AMO    -> AMO_DB
+/// - DBAR x + LL     -> LL
+/// - AMO_DB + DBAR x -> AMO_DB
+/// - AMO    + DBAR x -> AMO_DB
+/// - SC     + DBAR x -> SC
+///
+//===----------------------------------------------------------------------===//
+
+#include "LoongArch.h"
+#include "LoongArchInstrInfo.h"
+#include "LoongArchSubtarget.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachinePostDominators.h"
+#include "llvm/InitializePasses.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "loongarch-memory-barrier-opt"
+#define LOONGARCH_MEMORY_BARRIER_OPT_NAME                                      \
+  "LoongArch Memory Barrier Optimisation pass"
+
+static cl::opt<bool> RequireNoPathBypass(
+    "loongarch-require-no-path-bypass",
+    cl::desc("Optimize only when no paths bypass either memory barrier"),
+    cl::init(true), cl::Hidden);
+
+static cl::opt<bool> MergeAMOWithMB(
+    "loongarch-merge-amo-with-dbar",
+    cl::desc("Merge AMOs with DBARs into AMO_DB during optimization"),
+    cl::init(true), cl::Hidden);
+
+static cl::opt<bool> DisableInlineAsm(
+    "loongarch-disable-inline-asm-barrier-opt",
+    cl::desc("Disable optimization of memory barriers in InlineAsm"),
+    cl::init(false), cl::Hidden);
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wangleiat wrote:

Agreed.

https://github.com/llvm/llvm-project/pull/218597