[libclc][remangler] Teach the remangler to emit text (#8199)

Most llvm / UNIX tools accept input on stdin and emit it to stdout by
default.
Most llvm tools also allow emitting textual assembly rather than
bitcode. This isn't hugely important here as it's a build-time tool, but
it does make debugging easier.

As a side-effect of this change diagnostics go to stderr where they
should always go.

Author: ldrumm

libclc/utils/libclc-remangler/LibclcRemangler.cpp

@@ -70,7 +70,8 @@ static llvm::cl::OptionCategory
 static cl::opt<std::string>
     InputIRFilename("input-ir", cl::desc("<input bitcode>"),
                     cl::cat(LibCLCRemanglerToolCategory));
-static cl::opt<std::string> OutputFilename("o", cl::desc("Output filename"));
+static cl::opt<std::string> OutputFilename("o", cl::init("-"),
+                                           cl::desc("Output filename"));
 static cl::opt<SupportedLongWidth>
     LongWidth("long-width",
               cl::values(clEnumValN(SupportedLongWidth::L32, "l32",
@@ -87,6 +88,9 @@ static cl::opt<Signedness> CharSignedness(
 static cl::opt<bool> Verbose("v", cl::desc("Enable verbose output"),
                              cl::init(false),
                              cl::cat(LibCLCRemanglerToolCategory));
+static cl::opt<bool> TextualOut("S", cl::desc("Emit LLVM textual assembly"),
+                                cl::init(false),
+                                cl::cat(LibCLCRemanglerToolCategory));
 static cl::opt<bool> TestRun("t", cl::desc("Enable test run"), cl::init(false),
                              cl::cat(LibCLCRemanglerToolCategory));
 
@@ -842,8 +846,8 @@ class LibCLCRemangler : public ASTConsumer {
       Function *NewF = CloneFunction(Clonee, Dummy);
       NewF->setName(std::string(CloneName));
     } else if (Verbose) {
-      std::cout << "Could not create copy " << CloneName.data() << " : missing "
-                << CloneeName.data() << std::endl;
+      errs() << "Could not create copy " << CloneName.data() << " : missing "
+             << CloneeName.data() << '\n';
     }
 
     return true;
@@ -874,16 +878,15 @@ class LibCLCRemangler : public ASTConsumer {
 
     if (RemangledName != MangledName) {
       if (Verbose || TestRun) {
-        std::cout << "Mangling changed:"
-                  << "\n"
-                  << "Original:  " << MangledName << "\n"
-                  << "New:       " << RemangledName << "\n"
-                  << std::endl;
+        errs() << "Mangling changed:"
+               << "\n"
+               << "Original:  " << MangledName << "\n"
+               << "New:       " << RemangledName << "\n";
       }
       // In test run mode, where no substitution is made, change in mangling
       // name represents a failure. Report an error.
       if (TestRun) {
-        std::cout << "Test run failure!" << std::endl;
+        errs() << "Test run failure!\n";
         return false;
       }
       Func.setName(RemangledName);
@@ -934,12 +937,14 @@ class LibCLCRemangler : public ASTConsumer {
 
     if (TestRun) {
       if (Verbose)
-        std::cout << "Successfully processed: " << NumProcessed << " functions."
-                  << std::endl;
+        errs() << "Successfully processed: " << NumProcessed << " functions.\n";
       return;
     }
 
-    WriteBitcodeToFile(*M, Out->os());
+    if (TextualOut)
+      M->print(Out->os(), nullptr, true);
+    else
+      WriteBitcodeToFile(*M, Out->os());
 
     // Declare success.
     Out->keep();