[llvm-mc] Add reportWarning() to MCContext

[bcain]

Summary

Adding reportWarning() to MCContext, so that it can be used from
the Hexagon assembler backend.

[bcain]

Add context, add clang update.

[bcain]

ping! any comments or concerns about this change?

[bcain]

More context for this change:

• "--no-warn" is present already, target-independent, and it's supported by llvm-mc (and other MC tools) because it's already present in include/llvm/MC/MCTargetOptionsCommandFlags.inc.
• Only the AsmParser has access to the MCTargetOptions that contains NoWarn.
• This change adds a MCTargetOptions * to the MCContext so that assemblers can emit warnings outside of their AsmParser and still conform to --no-warn/--fatal-warnings.
• Hexagon has a check performed in its AsmBackend that can emit warnings, those warnings were not silenced by --no-warn.
• The .warning directive is already correctly silenced by llvm-mc --no-warn (but not clang -Wa,--no-warn).
• A corresponding change to clang has been added to support -Wa,--no-warn -- https://reviews.llvm.org/D61309

[sidneym]

LGTM

llvm/include/llvm/MC/MCContext.h

 #include "llvm/MC/MCAsmMacro.h"
 #include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/MC/MCTargetOptions.h"
 #include "llvm/MC/SectionKind.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Compiler.h"

     /// Do automatic reset in destructor
     bool AutoReset;
 
+    MCTargetOptions const *TargetOptions;
+
     bool HadError = false;
 
     MCSymbol *createSymbolImpl(const StringMapEntry<bool> *Name,

   public:
     explicit MCContext(const MCAsmInfo *MAI, const MCRegisterInfo *MRI,
                        const MCObjectFileInfo *MOFI,
-                       const SourceMgr *Mgr = nullptr, bool DoAutoReset = true);
+                       const SourceMgr *Mgr = nullptr,
+                       MCTargetOptions const *TargetOpts = nullptr,
+                       bool DoAutoReset = true);
     MCContext(const MCContext &) = delete;
     MCContext &operator=(const MCContext &) = delete;
     ~MCContext();

 
     bool hadError() { return HadError; }
     void reportError(SMLoc L, const Twine &Msg);
+    void reportWarning(SMLoc L, const Twine &Msg);
     // Unrecoverable error has occurred. Display the best diagnostic we can
     // and bail via exit(1). For now, most MC backend errors are unrecoverable.
     // FIXME: We should really do something about that.

llvm/lib/CodeGen/MachineModuleInfo.cpp

 }
 
 MachineModuleInfo::MachineModuleInfo(const LLVMTargetMachine *TM)
     : ImmutablePass(ID), TM(*TM),
       Context(TM->getMCAsmInfo(), TM->getMCRegisterInfo(),
-            TM->getObjFileLowering(), nullptr, false) {
+              TM->getObjFileLowering(), nullptr, nullptr, false) {
   initializeMachineModuleInfoPass(*PassRegistry::getPassRegistry());
 }
 

llvm/lib/MC/MCContext.cpp

 
 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
-                     bool DoAutoReset)
+                     MCTargetOptions const *TargetOpts, bool DoAutoReset)
     : SrcMgr(mgr), InlineSrcMgr(nullptr), MAI(mai), MRI(mri), MOFI(mofi),
       Symbols(Allocator), UsedNames(Allocator),
       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0),
-      AutoReset(DoAutoReset) {
+      AutoReset(DoAutoReset), TargetOptions(TargetOpts) {
   SecureLogFile = AsSecureLogFileName;
 
   if (SrcMgr && SrcMgr->getNumBuffers())

     report_fatal_error(Msg, false);
 }
 
+void MCContext::reportWarning(SMLoc Loc, const Twine &Msg) {
+  if (TargetOptions && TargetOptions->MCNoWarn)
+    return;
+  if (TargetOptions && TargetOptions->MCFatalWarnings)
+    reportError(Loc, Msg);
+  else {
+    // If we have a source manager use it. Otherwise, try using the inline
+    // source manager.
+    if (SrcMgr)
+      SrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
+    else if (InlineSrcMgr)
+      InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
+  }
+}
+
 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
   reportError(Loc, Msg);
 

llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCChecker.cpp

 }
 
 void HexagonMCChecker::reportWarning(Twine const &Msg) {
-  if (ReportErrors) {
-    auto SM = Context.getSourceManager();
-    if (SM)
-      SM->PrintMessage(MCB.getLoc(), SourceMgr::DK_Warning, Msg);
-  }
+  if (ReportErrors)
+    Context.reportWarning(MCB.getLoc(), Msg);
 }

llvm/test/MC/Hexagon/nowarn.s

+# RUN: llvm-mc -arch=hexagon -mhvx --filetype=asm %s -o - 2>&1 | FileCheck %s
+# RUN: llvm-mc --no-warn -arch=hexagon -mhvx --filetype=obj %s -o - | llvm-objdump -d - | FileCheck --check-prefix=CHECK-NOWARN %s
+# RUN: not llvm-mc --fatal-warnings -arch=hexagon -mhvx --filetype=asm %s 2>&1 | FileCheck --check-prefix=CHECK-FATAL-WARN %s
+
+  .text
+    .warning
+
+{
+  v7.tmp = vmem(r28 + #3)
+  v7:6.w = vadd(v17:16.w, v17:16.w)
+  v17:16.uw = vunpack(v8.uh)
+}
+
+# CHECK-NOWARN-NOT: warning
+# CHECK-FATAL-WARN-NOT: warning
+# CHECK-FATAL-WARN: error
+# CHECK-FATAL-WARN: error
+# CHECK: warning:
+# CHECK: warning:

llvm/tools/llvm-mc/llvm-mc.cpp

 static int AssembleInput(const char *ProgName, const Target *TheTarget,
                          SourceMgr &SrcMgr, MCContext &Ctx, MCStreamer &Str,
                          MCAsmInfo &MAI, MCSubtargetInfo &STI,
-                         MCInstrInfo &MCII, MCTargetOptions &MCOptions) {
+                         MCInstrInfo &MCII, MCTargetOptions const &MCOptions) {
   std::unique_ptr<MCAsmParser> Parser(
       createMCAsmParser(SrcMgr, Ctx, Str, MAI));
   std::unique_ptr<MCTargetAsmParser> TAP(

   cl::AddExtraVersionPrinter(TargetRegistry::printRegisteredTargetsForVersion);
 
   cl::ParseCommandLineOptions(argc, argv, "llvm machine code playground\n");
-  MCTargetOptions MCOptions = InitMCTargetOptionsFromFlags();
+  const MCTargetOptions MCOptions = InitMCTargetOptionsFromFlags();
   setDwarfDebugFlags(argc, argv);
 
   setDwarfDebugProducer();

   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and
   // MCObjectFileInfo needs a MCContext reference in order to initialize itself.
   MCObjectFileInfo MOFI;
-  MCContext Ctx(MAI.get(), MRI.get(), &MOFI, &SrcMgr);
+  MCContext Ctx(MAI.get(), MRI.get(), &MOFI, &SrcMgr, &MCOptions);
   MOFI.InitMCObjectFileInfo(TheTriple, PIC, Ctx, LargeCodeModel);
 
   if (SaveTempLabels)