[mips] Add assembler support for .set mips0 directive.

Summary:
This directive is used to reset the assembler options to their initial values.
Assembly programmers use it in conjunction with the ".set mipsX" directives.

This patch depends on the .set push/pop directive (http://reviews.llvm.org/D4821).

Contains work done by Matheus Almeida.

Reviewers: dsanders

Reviewed By: dsanders

Differential Revision: http://reviews.llvm.org/D4957

llvm-svn: 217438

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

@@ -177,6 +177,7 @@ class MipsAsmParser : public MCTargetAsmParser {
   const MCExpr *evaluateRelocExpr(const MCExpr *Expr, StringRef RelocStr);
 
   bool isEvaluated(const MCExpr *Expr);
+  bool parseSetMips0Directive();
   bool parseSetArchDirective();
   bool parseSetFeature(uint64_t Feature);
   bool parseDirectiveCPLoad(SMLoc Loc);
@@ -2731,6 +2732,19 @@ bool MipsAsmParser::parseSetAssignment() {
   return false;
 }
 
+bool MipsAsmParser::parseSetMips0Directive() {
+  Parser.Lex();
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return reportParseError("unexpected token, expected end of statement");
+
+  // Reset assembler options to their initial values.
+  setAvailableFeatures(AssemblerOptions.front()->getFeatures());
+  AssemblerOptions.back()->setFeatures(AssemblerOptions.front()->getFeatures());
+
+  getTargetStreamer().emitDirectiveSetMips0();
+  return false;
+}
+
 bool MipsAsmParser::parseSetArchDirective() {
   Parser.Lex();
   if (getLexer().isNot(AsmToken::Equal))
@@ -2981,6 +2995,8 @@ bool MipsAsmParser::parseDirectiveSet() {
     return false;
   } else if (Tok.getString() == "micromips") {
     return parseSetFeature(Mips::FeatureMicroMips);
+  } else if (Tok.getString() == "mips0") {
+    return parseSetMips0Directive();
   } else if (Tok.getString() == "mips1") {
     return parseSetFeature(Mips::FeatureMips1);
   } else if (Tok.getString() == "mips2") {

lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp

@@ -59,6 +59,7 @@ void MipsTargetStreamer::emitFMask(unsigned FPUBitmask, int FPUTopSavedRegOff) {
 void MipsTargetStreamer::emitDirectiveSetArch(StringRef Arch) {
   forbidModuleDirective();
 }
+void MipsTargetStreamer::emitDirectiveSetMips0() {}
 void MipsTargetStreamer::emitDirectiveSetMips1() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips2() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetMips3() { forbidModuleDirective(); }
@@ -184,6 +185,8 @@ void MipsTargetAsmStreamer::emitDirectiveSetArch(StringRef Arch) {
   MipsTargetStreamer::emitDirectiveSetArch(Arch);
 }
 
+void MipsTargetAsmStreamer::emitDirectiveSetMips0() { OS << "\t.set\tmips0\n"; }
+
 void MipsTargetAsmStreamer::emitDirectiveSetMips1() {
   OS << "\t.set\tmips1\n";
   MipsTargetStreamer::emitDirectiveSetMips1();

lib/Target/Mips/MipsTargetStreamer.h

@@ -49,6 +49,7 @@ public:
   virtual void emitFMask(unsigned FPUBitmask, int FPUTopSavedRegOff);
 
   virtual void emitDirectiveSetArch(StringRef Arch);
+  virtual void emitDirectiveSetMips0();
   virtual void emitDirectiveSetMips1();
   virtual void emitDirectiveSetMips2();
   virtual void emitDirectiveSetMips3();
@@ -151,6 +152,7 @@ public:
   void emitFMask(unsigned FPUBitmask, int FPUTopSavedRegOff) override;
 
   void emitDirectiveSetArch(StringRef Arch) override;
+  void emitDirectiveSetMips0() override;
   void emitDirectiveSetMips1() override;
   void emitDirectiveSetMips2() override;
   void emitDirectiveSetMips3() override;

test/MC/Mips/set-mips0-directive.s

@@ -0,0 +1,27 @@
+# RUN: llvm-mc %s -triple=mipsel-unknown-linux -mcpu=mips32r2 | \
+# RUN:   FileCheck %s
+
+    .text
+    rotr  $7, $7, 22
+
+    .set mips32r6
+    mod   $2, $4, $6
+    .set mips0
+    rotr  $2, $2, 15
+
+    .set mips3
+    dadd  $4, $4, $4
+    .set mips0
+    rotr  $3, $3, 19
+
+# CHECK: rotr  $7, $7, 22
+
+# CHECK: .set mips32r6
+# CHECK: mod   $2, $4, $6
+# CHECK: .set mips0
+# CHECK: rotr  $2, $2, 15
+
+# CHECK: .set mips3
+# CHECK: dadd  $4, $4, $4
+# CHECK: .set mips0
+# CHECK: rotr  $3, $3, 19