[llvm] [AsmPrinter][ELF] Support profile-guided section prefix for jump tables' (read-only) data sections (PR #122215)

[Snehasish Kumar via llvm-commits]

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@@ -0,0 +1,179 @@
+//===- StaticDataSplitter.cpp ---------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// The pass uses branch profile data to assign hotness based section qualifiers
+// for the following types of static data:
+// - Jump tables
+// - Constant pools (TODO)
+// - Other module-internal data (TODO)
+//
+// For the original RFC of this pass please see
+// https://discourse.llvm.org/t/rfc-profile-guided-static-data-partitioning/83744
+
+#include "llvm/ADT/ScopeExit.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ProfileSummaryInfo.h"
+#include "llvm/CodeGen/MBFIWrapper.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
+#include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "static-data-splitter"
+
+STATISTIC(NumHotJumpTables, "Number of hot jump tables seen");
+STATISTIC(NumColdJumpTables, "Number of cold jump tables seen");
+STATISTIC(NumUnknownJumpTables,
+          "Number of jump tables with unknown hotness. Option "
+          "-static-data-default-hotness specifies the hotness.");
+
+static cl::opt<MachineFunctionDataHotness> StaticDataDefaultHotness(
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snehasish wrote:

Do we need this option if we plan to keep unknown hotness in `rodata`? Then we can defer the decision to the linker about which sections to merge and we don't need the flexibility (and option) here.

https://github.com/llvm/llvm-project/pull/122215