bpf: Define instruction patterns for extensions and truncations between i32 to i64
bpf: Define instruction patterns for extensions and truncations between i32 to i64

For transformations between i32 and i64, if it is explicit signed extension:
  - first cast the operand to i64
  - then use SLL + SRA to finish the extension.

if it is explicit zero extension:
  - first cast the operand to i64
  - then use SLL + SRL to finish the extension.

if it is explicit any extension:
  - just refer to 64-bit register.

if it is explicit truncation:
  - just refer to 32-bit subregister.

NOTE: Some of the zero extension sequences might be unnecessary, they will be
removed by an peephole pass on MachineInstruction layer.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Yonghong Song <yhs@fb.com>

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@325981 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm