[llvm] [llvm][SystemZ] Set comment stream in SystemZDisassembler::getInstruction (PR #148614)

[David Spickett via llvm-commits]

https://github.com/DavidSpickett created https://github.com/llvm/llvm-project/pull/148614

This is done by other backends at the start of this function, for example AArch64Disassembler::getInstruction. Not setting it means you hit asserts in MCDisassembler::tryAddingSymbolicOperand and MCDisassembler::tryAddingPcLoadReferenceComment when there is a symbolizer set.

Which happened to me while debugging a SystemZ program using LLDB.

As the only good way to hit this path is from C++, I've copied X86's disassembler unit tests and added just enough to hit an assert if the comment stream is not set.

>From 7eb7635dd6138c315d5a0a1022265890756e27dd Mon Sep 17 00:00:00 2001
From: David Spickett <david.spickett at linaro.org>
Date: Mon, 14 Jul 2025 11:30:27 +0000
Subject: [PATCH] [llvm][SystemZ] Set comment stream in
 SystemZDisassembler::getInstruction

This is done by other backends at the start of this function, for example
AArch64Disassembler::getInstruction. Not setting it means you hit asserts
in MCDisassembler::tryAddingSymbolicOperand and MCDisassembler::tryAddingPcLoadReferenceComment
when there is a symbolizer set.

Which I found while debugging a SystemZ program using LLDB.

As the only good way to hit this path is from C++, I've copied
X86's disassembler unit tests and added just enough to hit
an assert, were it not for the changes in this PR.
---
 .../Disassembler/SystemZDisassembler.cpp      |   2 +
 llvm/unittests/MC/SystemZ/CMakeLists.txt      |   4 +-
 .../MC/SystemZ/SystemZMCDisassemblerTest.cpp  | 103 ++++++++++++++++++
 3 files changed, 108 insertions(+), 1 deletion(-)
 create mode 100644 llvm/unittests/MC/SystemZ/SystemZMCDisassemblerTest.cpp

diff --git a/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp b/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp
index 6ae529e974186..31b4f1196392c 100644
--- a/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp
+++ b/llvm/lib/Target/SystemZ/Disassembler/SystemZDisassembler.cpp
@@ -327,6 +327,8 @@ DecodeStatus SystemZDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                                  ArrayRef<uint8_t> Bytes,
                                                  uint64_t Address,
                                                  raw_ostream &CS) const {
+  CommentStream = &CS;
+
   // Get the first two bytes of the instruction.
   Size = 0;
   if (Bytes.size() < 2)
diff --git a/llvm/unittests/MC/SystemZ/CMakeLists.txt b/llvm/unittests/MC/SystemZ/CMakeLists.txt
index 3b7af4a3bbea3..a972ef27ddd8a 100644
--- a/llvm/unittests/MC/SystemZ/CMakeLists.txt
+++ b/llvm/unittests/MC/SystemZ/CMakeLists.txt
@@ -10,6 +10,8 @@ set(LLVM_LINK_COMPONENTS
   TargetParser
   )
 
-add_llvm_unittest(SystemZAsmLexerTests
+add_llvm_unittest(SystemZMCTests
   SystemZAsmLexerTest.cpp
+  SystemZMCDisassemblerTest.cpp
   )
+
diff --git a/llvm/unittests/MC/SystemZ/SystemZMCDisassemblerTest.cpp b/llvm/unittests/MC/SystemZ/SystemZMCDisassemblerTest.cpp
new file mode 100644
index 0000000000000..df59fcb402e21
--- /dev/null
+++ b/llvm/unittests/MC/SystemZ/SystemZMCDisassemblerTest.cpp
@@ -0,0 +1,103 @@
+//===- SystemZMCDisassemblerTest.cpp - Tests for SystemZ MCDisassembler ---===//
+//
+// 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 "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDisassembler/MCDisassembler.h"
+#include "llvm/MC/MCDisassembler/MCSymbolizer.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/MC/MCTargetOptions.h"
+#include "llvm/MC/TargetRegistry.h"
+#include "llvm/Support/TargetSelect.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+struct Context {
+  const char *TripleName = "systemz-unknown";
+  std::unique_ptr<MCRegisterInfo> MRI;
+  std::unique_ptr<MCAsmInfo> MAI;
+  std::unique_ptr<MCContext> Ctx;
+  std::unique_ptr<MCSubtargetInfo> STI;
+  std::unique_ptr<MCDisassembler> DisAsm;
+
+  Context() {
+    LLVMInitializeSystemZTargetInfo();
+    LLVMInitializeSystemZTargetMC();
+    LLVMInitializeSystemZDisassembler();
+
+    // If we didn't build SystemZ, do not run the test.
+    std::string Error;
+    const Target *TheTarget = TargetRegistry::lookupTarget(TripleName, Error);
+    if (!TheTarget)
+      return;
+
+    MRI.reset(TheTarget->createMCRegInfo(TripleName));
+    MAI.reset(TheTarget->createMCAsmInfo(*MRI, TripleName, MCTargetOptions()));
+    STI.reset(TheTarget->createMCSubtargetInfo(TripleName, "", ""));
+    Ctx = std::make_unique<MCContext>(Triple(TripleName), MAI.get(), MRI.get(),
+                                      STI.get());
+
+    DisAsm.reset(TheTarget->createMCDisassembler(*STI, *Ctx));
+  }
+
+  operator MCContext &() { return *Ctx; };
+};
+
+Context &getContext() {
+  static Context Ctxt;
+  return Ctxt;
+}
+
+class SystemZMCSymbolizerTest : public MCSymbolizer {
+public:
+  SystemZMCSymbolizerTest(MCContext &MC) : MCSymbolizer(MC, nullptr) {}
+  ~SystemZMCSymbolizerTest() {}
+
+  bool tryAddingSymbolicOperand([[maybe_unused]] MCInst &Inst,
+                                [[maybe_unused]] raw_ostream &CStream,
+                                [[maybe_unused]] int64_t Value,
+                                [[maybe_unused]] uint64_t Address,
+                                [[maybe_unused]] bool IsBranch,
+                                [[maybe_unused]] uint64_t Offset,
+                                [[maybe_unused]] uint64_t OpSize,
+                                [[maybe_unused]] uint64_t InstSize) override {
+    return true;
+  }
+
+  void
+  tryAddingPcLoadReferenceComment([[maybe_unused]] raw_ostream &cStream,
+                                  [[maybe_unused]] int64_t Value,
+                                  [[maybe_unused]] uint64_t Address) override {}
+};
+
+} // namespace
+
+TEST(SystemZDisassembler, SystemZMCSymbolizerTest) {
+  SystemZMCSymbolizerTest *TestSymbolizer =
+      new SystemZMCSymbolizerTest(getContext());
+  getContext().DisAsm->setSymbolizer(
+      std::unique_ptr<MCSymbolizer>(TestSymbolizer));
+
+  MCInst Inst;
+  uint64_t InstSize;
+
+  // Check that the SystemZ disassembler sets the comment stream before calling
+  // MCDisassembler::tryAddingSymbolicOperand. This will fail an assert if it
+  // does not do that.
+  MCDisassembler::DecodeStatus Status = getContext().DisAsm->getInstruction(
+      Inst, InstSize,
+      // lgrl   %r1, 0x1234
+      {0xc4, 0x18, 0x00, 0x00, 0x9a, 0x1a}, 0, nulls());
+  ASSERT_TRUE(Status == MCDisassembler::Success);
+  EXPECT_EQ(InstSize, uint64_t{6});
+}