release/21.x: [Hexagon][llvm-objdump] Start a fresh packet at symbol boundaries. (#163466)

[llvmbot]

Backport 0cdebda

Requested by: @quic-areg

[llvmbot]

@androm3da What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-llvm-binary-utilities

@llvm/pr-subscribers-backend-hexagon

Author: None (llvmbot)

Changes

Backport 0cdebda

Requested by: @quic-areg

---

Full diff: https://github.com/llvm/llvm-project/pull/163662.diff

3 Files Affected:

• (modified) llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp (+16)
• (added) llvm/test/tools/llvm-objdump/ELF/Hexagon/packet-reset-on-label.s (+23)
• (modified) llvm/tools/llvm-objdump/llvm-objdump.cpp (+8)

diff --git a/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp b/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp
index bcddb540d35dc..c48cf5e6353ac 100644
--- a/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp
+++ b/llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp
@@ -64,6 +64,10 @@ class HexagonDisassembler : public MCDisassembler {
 
   void remapInstruction(MCInst &Instr) const;
 
+  Expected<bool> onSymbolStart(SymbolInfoTy &Symbol, uint64_t &Size,
+                               ArrayRef<uint8_t> Bytes,
+                               uint64_t Address) const override;
+
 private:
   bool makeBundle(ArrayRef<uint8_t> Bytes, uint64_t Address,
                   uint64_t &BytesToSkip, raw_ostream &CS) const;
@@ -604,6 +608,18 @@ DecodeStatus HexagonDisassembler::getSingleInstruction(MCInst &MI, MCInst &MCB,
   return Result;
 }
 
+Expected<bool> HexagonDisassembler::onSymbolStart(SymbolInfoTy &Symbol,
+                                                  uint64_t &Size,
+                                                  ArrayRef<uint8_t> Bytes,
+                                                  uint64_t Address) const {
+  // At the start of a symbol, force a fresh packet by resetting any
+  // in-progress bundle state. This prevents packets from straddling label
+  // boundaries when data (e.g. jump tables) appears in between.
+  Size = 0;
+  resetBundle();
+  return true;
+}
+
 static DecodeStatus DecodeRegisterClass(MCInst &Inst, unsigned RegNo,
                                         ArrayRef<MCPhysReg> Table) {
   if (RegNo < Table.size()) {
diff --git a/llvm/test/tools/llvm-objdump/ELF/Hexagon/packet-reset-on-label.s b/llvm/test/tools/llvm-objdump/ELF/Hexagon/packet-reset-on-label.s
new file mode 100644
index 0000000000000..02a52bbb3fbd8
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/ELF/Hexagon/packet-reset-on-label.s
@@ -0,0 +1,23 @@
+// RUN: llvm-mc -triple=hexagon -mcpu=hexagonv75 -filetype=obj %s \
+// RUN:   | llvm-objdump -d - \
+// RUN:   | FileCheck %s
+
+foo:
+  { nop }
+  /// a nop without end-of-packet bits set to simulate data that is
+  /// not a proper packet end.
+  .long 0x7f004000
+bar:
+  { nop
+    nop
+  }
+
+// CHECK-LABEL: <foo>:
+// CHECK: { nop }
+// CHECK-NEXT: { nop
+
+/// The instruction starting after <bar> should start in a new packet.
+// CHECK-LABEL: <bar>:
+// CHECK: { nop
+// CHECK-NEXT: nop }
+
diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 74eb9033c8e2c..221b884e0c06c 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -717,11 +717,17 @@ class PrettyPrinter {
     } while (!Comments.empty());
     FOS.flush();
   }
+
+  // Hook invoked when starting to disassemble a symbol at the current position.
+  // Default is no-op.
+  virtual void onSymbolStart() {}
 };
 PrettyPrinter PrettyPrinterInst;
 
 class HexagonPrettyPrinter : public PrettyPrinter {
 public:
+  void onSymbolStart() override { reset(); }
+
   void printLead(ArrayRef<uint8_t> Bytes, uint64_t Address,
                  formatted_raw_ostream &OS) {
     if (LeadingAddr)
@@ -2216,6 +2222,8 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
         Start += Size;
         break;
       }
+      // Allow targets to reset any per-symbol state.
+      DT->Printer->onSymbolStart();
       formatted_raw_ostream FOS(OS);
       Index = Start;
       if (SectionAddr < StartAddress)

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