[mips] Add assembler support for the .set nodsp directive.

[tomatabacu]

Summary

This directive is used to tell the assembler to reject DSP-specific instructions.

[tomatabacu]

Fixed end of statement error reporting.
Added a comment.

[tomatabacu]

Rebased.

[dsanders]

LGTM

Could you follow up with a change to implement the '.set dsp' in a similar way?

Also, we should consider templating this kind of '.set foo'/'.set nofoo' directive since they are very similar to each other.

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

#include "MipsGenAsmMatcher.inc"
   bool parseDirectiveOption();
 
   bool parseSetAtDirective();
   bool parseSetNoAtDirective();
   bool parseSetMacroDirective();
   bool parseSetNoMacroDirective();
   bool parseSetMsaDirective();
   bool parseSetNoMsaDirective();
+  bool parseSetNoDspDirective();
   bool parseSetReorderDirective();
   bool parseSetNoReorderDirective();
   bool parseSetNoMips16Directive();
   bool parseSetFpDirective();
 
   bool parseSetAssignment();
 
   bool parseDataDirective(unsigned Size, SMLoc L);
bool MipsAsmParser::parseSetNoMsaDirective() {
   if (getLexer().isNot(AsmToken::EndOfStatement))
     return reportParseError("unexpected token in statement");
 
   clearFeatureBits(Mips::FeatureMSA, "msa");
   getTargetStreamer().emitDirectiveSetNoMsa();
   return false;
 }
 
+bool MipsAsmParser::parseSetNoDspDirective() {
+  Parser.Lex(); // Eat "nodsp".
+
+  // If this is not the end of the statement, report an error.
+  if (getLexer().isNot(AsmToken::EndOfStatement)) {
+    reportParseError("unexpected token, expected end of statement");
+    return false;
+  }
+
+  clearFeatureBits(Mips::FeatureDSP, "dsp");
+  getTargetStreamer().emitDirectiveSetNoDsp();
+  return false;
+}
+
 bool MipsAsmParser::parseSetNoMips16Directive() {
   Parser.Lex();
   // If this is not the end of the statement, report an error.
   if (getLexer().isNot(AsmToken::EndOfStatement)) {
     reportParseError("unexpected token in statement");
     return false;
   }
   // For now do nothing.
bool MipsAsmParser::parseDirectiveSet() {
   } else if (Tok.getString() == "mips64") {
     return parseSetFeature(Mips::FeatureMips64);
   } else if (Tok.getString() == "mips64r2") {
     return parseSetFeature(Mips::FeatureMips64r2);
   } else if (Tok.getString() == "mips64r6") {
     return parseSetFeature(Mips::FeatureMips64r6);
   } else if (Tok.getString() == "dsp") {
     return parseSetFeature(Mips::FeatureDSP);
+  } else if (Tok.getString() == "nodsp") {
+    return parseSetNoDspDirective();
   } else if (Tok.getString() == "msa") {
     return parseSetMsaDirective();
   } else if (Tok.getString() == "nomsa") {
     return parseSetNoMsaDirective();
   } else {
     // It is just an identifier, look for an assignment.
     parseSetAssignment();
     return false;

lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp

 void MipsTargetStreamer::emitDirectiveSetMips5() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips32() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips32R2() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips32R6() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips64() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips64R2() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips64R6() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetDsp() { forbidModuleDirective(); }
+void MipsTargetStreamer::emitDirectiveSetNoDsp() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveCpload(unsigned RegNo) {}
 void MipsTargetStreamer::emitDirectiveCpsetup(unsigned RegNo, int RegOrOffset,
                                               const MCSymbol &Sym, bool IsReg) {
 }
 void MipsTargetStreamer::emitDirectiveModuleOddSPReg(bool Enabled,
                                                      bool IsO32ABI) {
   if (!Enabled && !IsO32ABI)
     report_fatal_error("+nooddspreg is only valid for O32");
void MipsTargetAsmStreamer::emitDirectiveSetMips64R6() {
   OS << "\t.set\tmips64r6\n";
   MipsTargetStreamer::emitDirectiveSetMips64R6();
 }
 
 void MipsTargetAsmStreamer::emitDirectiveSetDsp() {
   OS << "\t.set\tdsp\n";
   MipsTargetStreamer::emitDirectiveSetDsp();
 }
+
+void MipsTargetAsmStreamer::emitDirectiveSetNoDsp() {
+  OS << "\t.set\tnodsp\n";
+  MipsTargetStreamer::emitDirectiveSetNoDsp();
+}
+
 // Print a 32 bit hex number with all numbers.
 static void printHex32(unsigned Value, raw_ostream &OS) {
   OS << "0x";
   for (int i = 7; i >= 0; i--)
     OS.write_hex((Value & (0xF << (i * 4))) >> (i * 4));
 }
 
 void MipsTargetAsmStreamer::emitMask(unsigned CPUBitmask,

lib/Target/Mips/MipsTargetStreamer.h

public:
   virtual void emitDirectiveSetMips5();
   virtual void emitDirectiveSetMips32();
   virtual void emitDirectiveSetMips32R2();
   virtual void emitDirectiveSetMips32R6();
   virtual void emitDirectiveSetMips64();
   virtual void emitDirectiveSetMips64R2();
   virtual void emitDirectiveSetMips64R6();
   virtual void emitDirectiveSetDsp();
+  virtual void emitDirectiveSetNoDsp();
 
   // PIC support
   virtual void emitDirectiveCpload(unsigned RegNo);
   virtual void emitDirectiveCpsetup(unsigned RegNo, int RegOrOffset,
                                     const MCSymbol &Sym, bool IsReg);
 
   /// Emit a '.module fp=value' directive using the given values.
   /// Updates the .MIPS.abiflags section
public:
   void emitDirectiveSetMips5() override;
   void emitDirectiveSetMips32() override;
   void emitDirectiveSetMips32R2() override;
   void emitDirectiveSetMips32R6() override;
   void emitDirectiveSetMips64() override;
   void emitDirectiveSetMips64R2() override;
   void emitDirectiveSetMips64R6() override;
   void emitDirectiveSetDsp() override;
+  void emitDirectiveSetNoDsp() override;
 
   // PIC support
   void emitDirectiveCpload(unsigned RegNo) override;
   void emitDirectiveCpsetup(unsigned RegNo, int RegOrOffset,
                             const MCSymbol &Sym, bool IsReg) override;
 
   // ABI Flags
   void emitDirectiveModuleFP(MipsABIFlagsSection::FpABIKind Value,

test/MC/Mips/set-nodsp.s

+# RUN: not llvm-mc %s -mcpu=mips32 -mattr=+dsp -triple mips-unknown-linux 2>%t1
+# RUN: FileCheck %s < %t1
+
+  lbux    $7, $10($11)
+
+  .set nodsp
+  lbux    $6, $10($11)
+  # CHECK: error: instruction requires a CPU feature not currently enabled
+
+  .set dsp
+  lbux    $5, $10($11)
+  # CHECK-NOT: error: instruction requires a CPU feature not currently enabled