[GISel]:IRTranslator: Prefer a buidInstr form that allows CSE of cast instructions
[GISel]:IRTranslator: Prefer a buidInstr form that allows CSE of cast instructions

https://reviews.llvm.org/D60844

Use the style of buildInstr that allows CSEing.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@358637 91177308-0d34-0410-b5e6-96231b3b80d8

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