Teach clang about the armv4/armv4t distinction

When choosing a default CPU, clang used to pick ARM7TDMI (which has Thumb) even
when the more restrictive armv4 triple was specified. This should fix that.

Patch by Jeroen Hofstee.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183905 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/ToolChain.cpp b/lib/Driver/ToolChain.cpp
index 71f5393..824db2a 100644
--- a/lib/Driver/ToolChain.cpp
+++ b/lib/Driver/ToolChain.cpp
@@ -177,7 +177,8 @@
     .Cases("armv2", "armv2a","arm2")
     .Case("armv3", "arm6")
     .Case("armv3m", "arm7m")
-    .Cases("armv4", "armv4t", "arm7tdmi")
+    .Case("armv4", "strongarm")
+    .Case("armv4t", "arm7tdmi")
     .Cases("armv5", "armv5t", "arm10tdmi")
     .Cases("armv5e", "armv5te", "arm1026ejs")
     .Case("armv5tej", "arm926ej-s")
@@ -196,7 +197,8 @@
     .Case("ep9312", "ep9312")
     .Case("iwmmxt", "iwmmxt")
     .Case("xscale", "xscale")
-    // If all else failed, return the most base CPU LLVM supports.
+    // If all else failed, return the most base CPU with thumb interworking
+    // supported by LLVM.
     .Default("arm7tdmi");
 }
 
@@ -207,6 +209,7 @@
 // FIXME: tblgen this, or kill it!
 static const char *getLLVMArchSuffixForARM(StringRef CPU) {
   return llvm::StringSwitch<const char *>(CPU)
+    .Case("strongarm", "v4")
     .Cases("arm7tdmi", "arm7tdmi-s", "arm710t", "v4t")
     .Cases("arm720t", "arm9", "arm9tdmi", "v4t")
     .Cases("arm920", "arm920t", "arm922t", "v4t")