[mips] Improve support for the .set mips16/nomips16 assembler directives.

[tomatabacu]

Summary

Appropriately set/clear the FeatureBit for Mips16 when these assembler directives are used and also emit ".set nomips16" (previously, only ".set mips16" was being emitted).

These improvements allow for better testing of the .cpload/.cprestore assembler directives (which are not supposed to work when Mips16 is enabled).

[tomatabacu]

Remove excess whitespace.

[dsanders]

You're right that MIPS16 hasn't been implemented for the integrated assembler yet. This adds some support and enables testing of .cpload/.cprestore so LGTM

Could you explain how you improved these directives in the commit message though. As written, it's not very helpful for those without the context.

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

#include "MipsGenAsmMatcher.inc"
   bool parseSetNoAtDirective();
   bool parseSetMacroDirective();
   bool parseSetNoMacroDirective();
   bool parseSetMsaDirective();
   bool parseSetNoMsaDirective();
   bool parseSetNoDspDirective();
   bool parseSetReorderDirective();
   bool parseSetNoReorderDirective();
+  bool parseSetMips16Directive();
   bool parseSetNoMips16Directive();
   bool parseSetFpDirective();
   bool parseSetPopDirective();
   bool parseSetPushDirective();
 
   bool parseSetAssignment();
 
   bool parseDataDirective(unsigned Size, SMLoc L);
if (getLexer().isNot(AsmToken::EndOfStatement)) {
     return false;
   }
 
   clearFeatureBits(Mips::FeatureDSP, "dsp");
   getTargetStreamer().emitDirectiveSetNoDsp();
   return false;
 }
 
+bool MipsAsmParser::parseSetMips16Directive() {
+  Parser.Lex(); // Eat "mips16".
+  
+  // 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;
+  }
+
+  setFeatureBits(Mips::FeatureMips16, "mips16");
+  getTargetStreamer().emitDirectiveSetMips16();
+  Parser.Lex(); // Consume the EndOfStatement.
+  return false;
+}
+
 bool MipsAsmParser::parseSetNoMips16Directive() {
-  Parser.Lex();
+  Parser.Lex(); // Eat "nomips16".
+  
   // 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;
   }
-  // For now do nothing.
+
+  clearFeatureBits(Mips::FeatureMips16, "mips16");
+  getTargetStreamer().emitDirectiveSetNoMips16();
   Parser.Lex(); // Consume the EndOfStatement.
   return false;
 }
 
 bool MipsAsmParser::parseSetFpDirective() {
   MipsABIFlagsSection::FpABIKind FpAbiVal;
   // Line can be: .set fp=32
   //              .set fp=xx
default:
     llvm_unreachable("Unimplemented feature");
   case Mips::FeatureDSP:
     setFeatureBits(Mips::FeatureDSP, "dsp");
     getTargetStreamer().emitDirectiveSetDsp();
     break;
   case Mips::FeatureMicroMips:
     getTargetStreamer().emitDirectiveSetMicroMips();
     break;
-  case Mips::FeatureMips16:
-    getTargetStreamer().emitDirectiveSetMips16();
-    break;
   case Mips::FeatureMips1:
     selectArch("mips1");
     getTargetStreamer().emitDirectiveSetMips1();
     break;
   case Mips::FeatureMips2:
     selectArch("mips2");
     getTargetStreamer().emitDirectiveSetMips2();
     break;
if (Tok.getString() == "noat") {
     return parseSetReorderDirective();
   } else if (Tok.getString() == "noreorder") {
     return parseSetNoReorderDirective();
   } else if (Tok.getString() == "macro") {
     return parseSetMacroDirective();
   } else if (Tok.getString() == "nomacro") {
     return parseSetNoMacroDirective();
   } else if (Tok.getString() == "mips16") {
-    return parseSetFeature(Mips::FeatureMips16);
+    return parseSetMips16Directive();
   } else if (Tok.getString() == "nomips16") {
     return parseSetNoMips16Directive();
   } else if (Tok.getString() == "nomicromips") {
     getTargetStreamer().emitDirectiveSetNoMicroMips();
     Parser.eatToEndOfStatement();
     return false;
   } else if (Tok.getString() == "micromips") {
     return parseSetFeature(Mips::FeatureMicroMips);

test/MC/Mips/set-mips16-directive.s

+# RUN: llvm-mc %s -arch=mips | FileCheck %s
+# FIXME: Update this test when we have a more mature implementation of Mips16 in the IAS.
+
+.text
+.set mips16
+.set nomips16
+
+# CHECK: .text
+# CHECK: .set mips16
+# CHECK: .set nomips16