Add support for Vector Subtract Carryout on PowerPC

Author: lu-zero

src/etc/platform-intrinsics/powerpc.json

@@ -79,6 +79,13 @@
             "llvm": "vsub{0.kind}{0.data_type_short}s",
             "ret": "i(8-32)",
             "args": ["0", "0"]
+        },
+        {
+            "intrinsic": "subc",
+            "width": [128],
+            "llvm": "vsubcuw",
+            "ret": "u32",
+            "args": ["0", "0"]
         }
     ]
 }

src/librustc_platform_intrinsics/powerpc.rs

@@ -172,6 +172,11 @@ pub fn find(name: &str) -> Option<Intrinsic> {
             output: &::U32x4,
             definition: Named("llvm.ppc.altivec.vsubuws")
         },
+        "_vec_subc" => Intrinsic {
+            inputs: { static INPUTS: [&'static Type; 2] = [&::U32x4, &::U32x4]; &INPUTS },
+            output: &::U32x4,
+            definition: Named("llvm.ppc.altivec.vsubcuw")
+        },
         _ => return None,
     })
 }