[NFC][llvm-objdump] Add quiet disassembly

Add a boolean to control whether object disassembly
(disassembleObject()) prints to console. It is always set to `false`
which makes this change an NFC.

This is introduced to support the upcoming `--call-graph-info` option
which will utilize the `disassembleObject` function to collect function
and call site addresses.

Author: Prabhuk

llvm/tools/llvm-objdump/llvm-objdump.cpp

@@ -349,6 +349,7 @@ bool objdump::UnwindInfo;
 static bool Wide;
 std::string objdump::Prefix;
 uint32_t objdump::PrefixStrip;
+static bool QuietDisasm = false;
 
 DebugVarsFormat objdump::DbgVariables = DVDisabled;
 
@@ -1374,6 +1375,8 @@ static uint64_t dumpARMELFData(uint64_t SectionAddr, uint64_t Index,
   return 1;
 }
 
+static raw_ostream &disasmOuts() { return QuietDisasm ? nulls() : outs(); }
+
 static void dumpELFData(uint64_t SectionAddr, uint64_t Index, uint64_t End,
                         ArrayRef<uint8_t> Bytes) {
   // print out data up to 8 bytes at a time in hex and ascii
@@ -1383,9 +1386,9 @@ static void dumpELFData(uint64_t SectionAddr, uint64_t Index, uint64_t End,
 
   for (; Index < End; ++Index) {
     if (NumBytes == 0)
-      outs() << format("%8" PRIx64 ":", SectionAddr + Index);
+      disasmOuts() << format("%8" PRIx64 ":", SectionAddr + Index);
     Byte = Bytes.slice(Index)[0];
-    outs() << format(" %02x", Byte);
+    disasmOuts() << format(" %02x", Byte);
     AsciiData[NumBytes] = isPrint(Byte) ? Byte : '.';
 
     uint8_t IndentOffset = 0;
@@ -1400,9 +1403,9 @@ static void dumpELFData(uint64_t SectionAddr, uint64_t Index, uint64_t End,
     }
     if (NumBytes == 8) {
       AsciiData[8] = '\0';
-      outs() << std::string(IndentOffset, ' ') << "         ";
-      outs() << reinterpret_cast<char *>(AsciiData);
-      outs() << '\n';
+      disasmOuts() << std::string(IndentOffset, ' ') << "         ";
+      disasmOuts() << reinterpret_cast<char *>(AsciiData);
+      disasmOuts() << '\n';
       NumBytes = 0;
     }
   }
@@ -2089,10 +2092,10 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
 
       if (!PrintedSection) {
         PrintedSection = true;
-        outs() << "\nDisassembly of section ";
+        disasmOuts() << "\nDisassembly of section ";
         if (!SegmentName.empty())
-          outs() << SegmentName << ",";
-        outs() << SectionName << ":\n";
+          disasmOuts() << SegmentName << ",";
+        disasmOuts() << SectionName << ":\n";
       }
 
       bool PrintedLabel = false;
@@ -2104,22 +2107,24 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
         const StringRef SymbolName = SymNamesHere[i];
 
         if (!PrintedLabel) {
-          outs() << '\n';
+          disasmOuts() << '\n';
           PrintedLabel = true;
         }
         if (LeadingAddr)
-          outs() << format(Is64Bits ? "%016" PRIx64 " " : "%08" PRIx64 " ",
-                           SectionAddr + Start + VMAAdjustment);
+          disasmOuts() << format(Is64Bits ? "%016" PRIx64 " "
+                                          : "%08" PRIx64 " ",
+                                 SectionAddr + Start + VMAAdjustment);
         if (Obj.isXCOFF() && SymbolDescription) {
-          outs() << getXCOFFSymbolDescription(Symbol, SymbolName) << ":\n";
+          disasmOuts() << getXCOFFSymbolDescription(Symbol, SymbolName)
+                       << ":\n";
         } else
-          outs() << '<' << SymbolName << ">:\n";
+          disasmOuts() << '<' << SymbolName << ">:\n";
       }
 
       // Don't print raw contents of a virtual section. A virtual section
       // doesn't have any contents in the file.
       if (Section.isVirtual()) {
-        outs() << "...\n";
+        disasmOuts() << "...\n";
         continue;
       }
 
@@ -2156,17 +2161,17 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
           do {
             StringRef Line;
             std::tie(Line, ErrMsg) = ErrMsg.split('\n');
-            outs() << DT->Context->getAsmInfo()->getCommentString()
-                   << " error decoding " << SymNamesHere[SHI] << ": " << Line
-                   << '\n';
+            disasmOuts() << DT->Context->getAsmInfo()->getCommentString()
+                         << " error decoding " << SymNamesHere[SHI] << ": "
+                         << Line << '\n';
           } while (!ErrMsg.empty());
 
           if (Size) {
-            outs() << DT->Context->getAsmInfo()->getCommentString()
-                   << " decoding failed region as bytes\n";
+            disasmOuts() << DT->Context->getAsmInfo()->getCommentString()
+                         << " decoding failed region as bytes\n";
             for (uint64_t I = 0; I < Size; ++I)
-              outs() << "\t.byte\t " << format_hex(Bytes[I], 1, /*Upper=*/true)
-                     << '\n';
+              disasmOuts() << "\t.byte\t "
+                           << format_hex(Bytes[I], 1, /*Upper=*/true) << '\n';
           }
         }
 
@@ -2203,7 +2208,7 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
           Symbols[SI - 1].XCOFFSymInfo.StorageMappingClass &&
           (*Symbols[SI - 1].XCOFFSymInfo.StorageMappingClass == XCOFF::XMC_PR);
 
-      formatted_raw_ostream FOS(outs());
+      formatted_raw_ostream FOS(disasmOuts());
 
       std::unordered_map<uint64_t, std::string> AllLabels;
       std::unordered_map<uint64_t, std::vector<BBAddrMapLabel>> BBAddrMapLabels;
@@ -2551,6 +2556,7 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
       set_difference(DisasmSymbolSet, FoundDisasmSymbolSet);
   for (StringRef Sym : MissingDisasmSymbolSet.keys())
     reportWarning("failed to disassemble missing symbol " + Sym, FileName);
+  QuietDisasm = false;
 }
 
 static void disassembleObject(ObjectFile *Obj, bool InlineRelocs) {