Backport to 0.8 branch for LLVM6

.travis.yml

@@ -1,23 +1,40 @@
 language: rust
 cache: cargo
+rust: nightly
 
 matrix:
+  fast_finish: true
   include:
+    - name: "Check with Clippy"
+      install:
+        - rustup component add clippy
+      script:
+        - cargo clippy -- --verbose
+
+    - name: "Check with Rustfmt"
+      install:
+        - rustup component add rustfmt
+      script:
+        - cargo fmt -- --check
+
     - name: "x86_64-unknown-linux-gnu"
       os: linux
-      rust: nightly
 
     - name: "x86_64-apple-darwin"
       os: osx
       osx_image: xcode10
-      rust: nightly
+
+before_install:
+  - rustup target add nvptx64-nvidia-cuda
 
 script:
-  - rustup component add rust-src
-  - cargo install -f xargo
-  - cargo check
-  - cargo test
+  - cargo test --verbose
 
 notifications:
   email:
     on_success: never
+
+branches:
+  only:
+    - master
+    - /^v\d+\.\d+\.\d+.*$/