message: Add FPToSI/FPExt/FPTrunc cast ops to the LLVM dialect.
  Closes
  COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/mlir/pull/99 from schweitzpgi:cast-ops
diff: @@ -300,6 +300,9 @@ def LLVM_SExtOp : LLVM_CastOp<"sext", "CreateSExt">;
  def LLVM_ZExtOp : LLVM_CastOp<"zext", "CreateZExt">;
  def LLVM_TruncOp : LLVM_CastOp<"trunc", "CreateTrunc">;
  def LLVM_SIToFPOp : LLVM_CastOp<"sitofp", "CreateSIToFP">;
  +def LLVM_FPToSIOp : LLVM_CastOp<"fptosi", "CreateFPToSI">;
  +def LLVM_FPExtOp : LLVM_CastOp<"fpext", "CreateFPExt">;
  +def LLVM_FPTruncOp : LLVM_CastOp<"fptrunc", "CreateFPTrunc">;
  // Call-related operations.
  def LLVM_CallOp : LLVM_Op<"call">,
  