Correctly handle the degenerated triple "thumb".

Fixes a crash in llc where some parts think the target is thumb and others think
it is ARM.

llvm-svn: 197607
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
index 903b5d3..400dab7 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
@@ -89,14 +89,11 @@
   unsigned Idx = 0;
 
   // FIXME: Enhance Triple helper class to extract ARM version.
-  bool isThumb = false;
+  bool isThumb = triple.getArch() == Triple::thumb;
   if (Len >= 5 && TT.substr(0, 4) == "armv")
     Idx = 4;
-  else if (Len >= 6 && TT.substr(0, 5) == "thumb") {
-    isThumb = true;
-    if (Len >= 7 && TT[5] == 'v')
-      Idx = 6;
-  }
+  else if (Len >= 7 && TT.substr(0, 6) == "thumbv")
+    Idx = 6;
 
   bool NoCPU = CPU == "generic" || CPU.empty();
   std::string ARMArchFeature;