utils: Remove some no-op raw_string_ostream flush calls, NFC

Since 65b13610a5, raw_string_ostream has
been unbuffered by default. Based on an audit of llvm/utils/, this
commit removes every call to `raw_string_ostream::flush()` and any call
to `raw_string_ostream::str()` whose result is ignored or that doesn't
help with clarity.

I left behind a few calls to `str()`. In these cases, the underlying
std::string was declared pretty far away and never used again, whereas
stream recently had its last write. The code is easier to read as-is;
the no-op call to `flush()` inside `str()` isn't harmful, and when
https://reviews.llvm.org/D115421 lands it'll be gone anyway.

llvm/utils/FileCheck/FileCheck.cpp

@@ -415,7 +415,6 @@ BuildInputAnnotations(const SourceMgr &SM, unsigned CheckFileBufferID,
                        "the check file or for an implicit pattern");
     if (DiagCountPerPattern[DiagItr->CheckLoc] > 1)
       Label << "'" << DiagIndexPerPattern[DiagItr->CheckLoc]++;
-    Label.flush();
     LabelWidth = std::max((std::string::size_type)LabelWidth, A.Label.size());
 
     A.Marker = GetMarker(DiagItr->MatchTy);

llvm/utils/TableGen/AsmWriterEmitter.cpp

@@ -757,8 +757,6 @@ public:
         ++I;
       }
     }
-
-    OS.flush();
     return OutString;
   }
 

llvm/utils/TableGen/CodeEmitterGen.cpp

@@ -515,7 +515,7 @@ void CodeEmitterGen::run(raw_ostream &o) {
     << "    std::string msg;\n"
     << "    raw_string_ostream Msg(msg);\n"
     << "    Msg << \"Not supported instr: \" << MI;\n"
-    << "    report_fatal_error(Msg.str().c_str());\n"
+    << "    report_fatal_error(msg.c_str());\n"
     << "  }\n";
   if (UseAPInt)
     o << "  Inst = Value;\n";

llvm/utils/TableGen/CodeGenDAGPatterns.cpp

@@ -1583,7 +1583,7 @@ static TreePatternNode *getOperandNum(unsigned OpNo, TreePatternNode *N,
     OS << "Invalid operand number in type constraint "
            << (OpNo+NumResults) << " ";
     N->print(OS);
-    PrintFatalError(OS.str());
+    PrintFatalError(S);
   }
 
   return N->getChild(OpNo);

llvm/utils/TableGen/DAGISelMatcherEmitter.cpp

@@ -169,7 +169,6 @@ static std::string GetPatFromTreePatternNode(const TreePatternNode *N) {
   std::string str;
   raw_string_ostream Stream(str);
   Stream << *N;
-  Stream.str();
   return str;
 }
 
@@ -235,7 +234,6 @@ static std::string getIncludePath(const Record *R) {
 
   Stream << SrcMgr.getBufferInfo(CurBuf).Buffer->getBufferIdentifier() << ":"
          << SrcMgr.FindLineNumber(L, CurBuf);
-  Stream.str();
   return str;
 }
 

llvm/utils/TableGen/DAGISelMatcherGen.cpp

@@ -267,7 +267,7 @@ void MatcherGen::EmitLeafMatchCode(const TreePatternNode *N) {
       std::string S;
       raw_string_ostream OS(S);
       OS << "We expect complex pattern uses to have names: " << *N;
-      PrintFatalError(OS.str());
+      PrintFatalError(S);
     }
 
     // Remember this ComplexPattern so that we can emit it after all the other

llvm/utils/TableGen/FastISelEmitter.cpp

@@ -568,7 +568,6 @@ void FastISelMap::collectPatterns(CodeGenDAGPatterns &CGP) {
     std::string ManglingSuffix;
     raw_string_ostream SuffixOS(ManglingSuffix);
     Operands.PrintManglingSuffix(SuffixOS, ImmediatePredicates, true);
-    SuffixOS.flush();
     if (!StringSwitch<bool>(ManglingSuffix)
         .Cases("", "r", "rr", "ri", "i", "f", true)
         .Default(false))

llvm/utils/TableGen/GICombinerEmitter.cpp

@@ -633,7 +633,7 @@ void GICombinerEmitter::emitNameMatcher(raw_ostream &OS) const {
     raw_string_ostream SS(Code);
     SS << "return " << EnumeratedRule.getID() << ";\n";
     Cases.push_back(
-        std::make_pair(std::string(EnumeratedRule.getName()), SS.str()));
+        std::make_pair(std::string(EnumeratedRule.getName()), Code));
   }
 
   OS << "static Optional<uint64_t> getRuleIdxForIdentifier(StringRef "

llvm/utils/TableGen/GlobalISelEmitter.cpp

@@ -109,7 +109,7 @@ public:
     raw_string_ostream OS(Str);
 
     emitCxxEnumValue(OS);
-    return OS.str();
+    return Str;
   }
 
   void emitCxxEnumValue(raw_ostream &OS) const {
@@ -1673,7 +1673,7 @@ public:
         CommentOS << "Operand " << OpIdx;
       else
         CommentOS << SymbolicName;
-      Table << MatchTable::Comment(CommentOS.str()) << MatchTable::LineBreak;
+      Table << MatchTable::Comment(Comment) << MatchTable::LineBreak;
     }
 
     emitPredicateListOpcodes(Table, Rule);

llvm/utils/TableGen/PredicateExpander.cpp

@@ -233,7 +233,6 @@ void PredicateExpander::expandReturnStatement(raw_ostream &OS,
   SS << "return ";
   expandPredicate(SS, Rec);
   SS << ";";
-  SS.flush();
   OS << Buffer;
 }
 
@@ -276,7 +275,6 @@ void PredicateExpander::expandOpcodeSwitchStatement(raw_ostream &OS,
 
   SS.indent(getIndentLevel() * 2);
   SS << "} // end of switch-stmt";
-  SS.flush();
   OS << Buffer;
 }
 

llvm/utils/TableGen/SubtargetEmitter.cpp

@@ -1433,7 +1433,6 @@ static void emitPredicateProlog(const RecordKeeper &Records, raw_ostream &OS) {
   for (Record *P : Prologs)
     Stream << P->getValueAsString("Code") << '\n';
 
-  Stream.flush();
   OS << Buffer;
 }
 
@@ -1492,7 +1491,6 @@ static void emitPredicates(const CodeGenSchedTransition &T,
   }
 
   SS << "return " << T.ToClassIdx << "; // " << SC.Name << '\n';
-  SS.flush();
   OS << Buffer;
 }
 

llvm/utils/yaml-bench/YAMLBench.cpp

@@ -184,12 +184,10 @@ static std::string createJSONText(size_t MemoryMB, unsigned ValueSize) {
            << "  \"key2\": \"" << std::string(ValueSize, '*') << "\",\n"
            << "  \"key3\": \"" << std::string(ValueSize, '*') << "\"\n"
            << " }";
-    Stream.flush();
     if (JSONText.size() < MemoryBytes) Stream << ",";
     Stream << "\n";
   }
   Stream << "]\n";
-  Stream.flush();
   return JSONText;
 }