[hexagon] add a -mcabac flag

For v73 and later, clang users who wish to use the cabac instructions need
a way to add the 'cabac' target feature.

Reviewed By: kparzysz

Differential Revision: https://reviews.llvm.org/D142947

(cherry picked from commit cd97675)

Author: androm3da

clang/include/clang/Driver/Options.td

@@ -4559,6 +4559,8 @@ def mnvs : Flag<["-"], "mnvs">, Group<m_hexagon_Features_Group>,
   Flags<[CC1Option]>, HelpText<"Enable generation of new-value stores">;
 def mno_nvs : Flag<["-"], "mno-nvs">, Group<m_hexagon_Features_Group>,
   Flags<[CC1Option]>, HelpText<"Disable generation of new-value stores">;
+def mcabac: Flag<["-"], "mcabac">, Group<m_hexagon_Features_Group>,
+  HelpText<"Enable CABAC instructions">;
 
 // SPARC feature flags
 def mfpu : Flag<["-"], "mfpu">, Group<m_sparc_Features_Group>;

clang/test/Driver/hexagon-toolchain-elf.c

@@ -581,6 +581,16 @@
 // RUN:        | FileCheck --check-prefix=CHECK371 %s
 // CHECK371-NOT: "+reserved-r19"
 
+// -----------------------------------------------------------------------------
+// mcabac
+// -----------------------------------------------------------------------------
+// RUN: %clang -### -target hexagon-unknown-elf -mcabac %s 2>&1 \
+// RUN:        | FileCheck --check-prefix=CHECK372 %s
+// CHECK372: "-target-feature" "+cabac"
+// RUN: %clang -### -target hexagon-unknown-elf %s 2>&1 \
+// RUN:        | FileCheck --check-prefix=CHECK373 %s
+// CHECK373-NOT: "+cabac"
+
 // -----------------------------------------------------------------------------
 // Misc Defaults
 // -----------------------------------------------------------------------------