Driver: force restricted IT blocks for Windows on ARM

Windows on ARM expects ARMv8 (restricted IT) conditional instructions only.
Force enable the restricted IT mode via the backend option when targeting WoA.

llvm-svn: 209086

clang/lib/Driver/Tools.cpp

@@ -3451,6 +3451,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back("-backend-option");
       CmdArgs.push_back("-arm-no-restrict-it");
     }
+  } else if (TT.isOSWindows() && (TT.getArch() == llvm::Triple::arm ||
+                                  TT.getArch() == llvm::Triple::thumb)) {
+    // Windows on ARM expects restricted IT blocks
+    CmdArgs.push_back("-backend-option");
+    CmdArgs.push_back("-arm-restrict-it");
   }
 
   // Forward -f options with positive and negative forms; we translate

clang/test/Driver/woa-restrict-it.c

@@ -0,0 +1,4 @@
+// RUN: %clang -target armv7-windows -### %s 2>&1 | FileCheck %s
+
+// CHECK: "-backend-option" "-arm-restrict-it"
+