[llvm] r225521 - [mips] Add comment which explains why we need to change the assembler options before and after inline asm blocks. NFC.

[Toma Tabacu]

Author: tomatabacu
Date: Fri Jan  9 09:00:30 2015
New Revision: 225521

URL: http://llvm.org/viewvc/llvm-project?rev=225521&view=rev
Log:
[mips] Add comment which explains why we need to change the assembler options before and after inline asm blocks. NFC.

Modified:
    llvm/trunk/lib/Target/Mips/MipsAsmPrinter.cpp

Modified: llvm/trunk/lib/Target/Mips/MipsAsmPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/MipsAsmPrinter.cpp?rev=225521&r1=225520&r2=225521&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Mips/MipsAsmPrinter.cpp (original)
+++ llvm/trunk/lib/Target/Mips/MipsAsmPrinter.cpp Fri Jan  9 09:00:30 2015
@@ -747,6 +747,12 @@ void MipsAsmPrinter::emitInlineAsmStart(
     const MCSubtargetInfo &StartInfo) const {
   MipsTargetStreamer &TS = getTargetStreamer();
 
+  // GCC's choice of assembler options for inline assembly code ('at', 'macro'
+  // and 'reorder') is different from LLVM's choice for generated code ('noat',
+  // 'nomacro' and 'noreorder').
+  // In order to maintain compatibility with inline assembly code which depends
+  // on GCC's assembler options being used, we have to switch to those options
+  // for the duration of the inline assembly block and then switch back.
   TS.emitDirectiveSetPush();
   TS.emitDirectiveSetAt();
   TS.emitDirectiveSetMacro();