ARM push of a single register encodes as pre-indexed STR.

Per the ARM ARM, a 'push' of a single register encodes as an STR,
not an STM.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137318 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
index a8008faa..af04355 100644
--- a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
+++ b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
@@ -88,6 +88,13 @@
     printRegisterList(MI, 4, O);
     return;
   }
+  if (Opcode == ARM::STR_PRE_IMM && MI->getOperand(2).getReg() == ARM::SP &&
+      MI->getOperand(3).getImm() == -4) {
+    O << '\t' << "push";
+    printPredicateOperand(MI, 4, O);
+    O << "\t{" << getRegisterName(MI->getOperand(1).getReg()) << "}";
+    return;
+  }
 
   // A8.6.122 POP
   if ((Opcode == ARM::LDMIA_UPD || Opcode == ARM::t2LDMIA_UPD) &&