[mips] Tolerate the use of the %z inline asm operand modifier with non-immediates.

Summary:
Currently, we give an error if %z is used with non-immediates, instead of continuing as if the %z isn't there.

For example, you use the %z operand modifier along with the "Jr" constraints ("r" makes the operand a register, and "J" makes it an immediate, but only if its value is 0). 
In this case, you want the compiler to print "$0" if the inline asm input operand turns out to be an immediate zero and you want it to print the register containing the operand, if it's not.

We give an error in the latter case, and we shouldn't (GCC also doesn't).

Reviewers: dsanders

Reviewed By: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6023

llvm-svn: 221453

1 files changed, 5 insertions, 7 deletions

diff --git a/llvm/lib/Target/Mips/MipsAsmPrinter.cpp b/llvm/lib/Target/Mips/MipsAsmPrinter.cpp
index 43ef3790802..1b4cb616cc6 100644
--- a/llvm/lib/Target/Mips/MipsAsmPrinter.cpp
+++ b/llvm/lib/Target/Mips/MipsAsmPrinter.cpp
@@ -473,14 +473,12 @@ bool MipsAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
       return false;
     case 'z': {
       // $0 if zero, regular printing otherwise
-      if (MO.getType() != MachineOperand::MO_Immediate)
-        return true;
-      int64_t Val = MO.getImm();
-      if (Val)
-        O << Val;
-      else
+      if (MO.getType() == MachineOperand::MO_Immediate && MO.getImm() == 0) {
         O << "$0";
-      return false;
+        return false;
+      }
+      // If not, call printOperand as normal.
+      break;
     }
     case 'D': // Second part of a double word register operand
     case 'L': // Low order register of a double word register operand