[mips] Set GCC-compatible MIPS asssembler options before inline asm blocks.

Summary:
When generating MIPS assembly, LLVM always overrides the default assembler options by emitting the '.set noreorder', '.set nomacro' and '.set noat' directives,
while GCC uses the default options if an assembly-level function contains inline assembly code.

This becomes a problem when the code generated by LLVM is interleaved with inline assembly which assumes GCC-like assembler options (from Linux, for example).

This patch fixes these conflicts by setting the appropriate assembler options at the beginning of an inline asm block and popping them at the end.

Reviewers: dsanders

Reviewed By: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6637

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224425 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp

@@ -90,6 +90,7 @@ void AsmPrinter::EmitInlineAsm(StringRef Str, const MDNode *LocMDNode,
   assert(MCAI && "No MCAsmInfo");
   if (!MCAI->useIntegratedAssembler() &&
       !OutStreamer.isIntegratedAssemblerRequired()) {
+    emitInlineAsmStart(TM.getSubtarget<MCSubtargetInfo>());
     OutStreamer.EmitRawText(Str);
     emitInlineAsmEnd(TM.getSubtarget<MCSubtargetInfo>(), nullptr);
     return;
@@ -152,6 +153,7 @@ void AsmPrinter::EmitInlineAsm(StringRef Str, const MDNode *LocMDNode,
     TAP->SetFrameRegister(TRI->getFrameRegister(*MF));
   }
 
+  emitInlineAsmStart(STIOrig);
   // Don't implicitly switch to the text section before the asm.
   int Res = Parser->Run(/*NoInitialTextSection*/ true,
                         /*NoFinalize*/ true);
@@ -567,5 +569,7 @@ bool AsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
   return true;
 }
 
+void AsmPrinter::emitInlineAsmStart(const MCSubtargetInfo &StartInfo) const {}
+
 void AsmPrinter::emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
                                   const MCSubtargetInfo *EndInfo) const {}