[llvm] [BOLT][RISCV] Add target symbolizer for relocations (PR #217944)

[Pengcheng Wang via llvm-commits]

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@@ -0,0 +1,150 @@
+//===- bolt/Target/RISCV/RISCVMCSymbolizer.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
+//
+//===----------------------------------------------------------------------===//
+
+#include "RISCVMCSymbolizer.h"
+#include "bolt/Core/BinaryContext.h"
+#include "bolt/Core/BinaryFunction.h"
+#include "bolt/Core/MCPlusBuilder.h"
+#include "bolt/Core/Relocation.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/MC/MCInst.h"
+
+#define DEBUG_TYPE "bolt-symbolizer"
+
+namespace llvm {
+namespace bolt {
+
+RISCVMCSymbolizer::RISCVMCSymbolizer(BinaryFunction &Function,
+                                     bool CreateNewSymbols)
+    : MCSymbolizer(*Function.getBinaryContext().Ctx, nullptr),
+      Function(Function), CreateNewSymbols(CreateNewSymbols) {
+  // Discover instruction references before decoding starts. This lets us
+  // attach a label while decoding the referenced %pcrel_hi instruction even
+  // though its %pcrel_lo user is normally decoded later.
+  for (uint64_t SearchOffset = 0; SearchOffset < Function.getSize();) {
+    const Relocation *Rel =
+        Function.getRelocationInRange(SearchOffset, Function.getSize());
+    if (!Rel)
+      break;
+
+    if (Relocation::isInstructionReference(Rel->Type)) {
+      assert(Rel->Value >= Function.getAddress() &&
+             Rel->Value < Function.getAddress() + Function.getSize() &&
+             "RISC-V instruction reference outside of function");
+      const uint64_t ReferencedOffset = Rel->Value - Function.getAddress();
+      InstructionReferences.try_emplace(ReferencedOffset, Rel);
+      if (CreateNewSymbols)
+        InstructionLabels.try_emplace(ReferencedOffset, nullptr);
+    }
+
+    SearchOffset = Rel->Offset + 1;
+  }
+}
+
+RISCVMCSymbolizer::~RISCVMCSymbolizer() {}
+
+MCSymbol *RISCVMCSymbolizer::getOrCreateInstructionLabel(uint64_t Offset) {
+  auto [It, Inserted] = InstructionLabels.try_emplace(Offset, nullptr);
+  (void)Inserted;
----------------
wangpc-pp wrote:

```suggestion
  auto [It, _] = InstructionLabels.try_emplace(Offset, nullptr);
```

https://github.com/llvm/llvm-project/pull/217944