-- | Imperative code with an OpenCL component.
--
-- Apart from ordinary imperative code, this also carries around an
-- OpenCL program as a string, as well as a list of kernels defined by
-- the OpenCL program.
--
-- The imperative code has been augmented with a 'LaunchKernel'
-- operation that allows one to execute an OpenCL kernel.
module Futhark.CodeGen.ImpCode.OpenCL
       ( Program (..)
       , Function
       , FunctionT (Function)
       , Code
       , KernelName
       , KernelArg (..)
       , OpenCL (..)
       , KernelSafety(..)
       , numFailureParams
       , KernelTarget (..)
       , FailureMsg(..)
       , module Futhark.CodeGen.ImpCode
       , module Futhark.IR.Kernels.Sizes
       )
       where

import qualified Data.Map as M

import Futhark.CodeGen.ImpCode hiding (Function, Code)
import Futhark.IR.Kernels.Sizes
import qualified Futhark.CodeGen.ImpCode as Imp

import Futhark.Util.Pretty

-- | An program calling OpenCL kernels.
data Program = Program { openClProgram :: String
                       , openClPrelude :: String
                         -- ^ Must be prepended to the program.
                       , openClKernelNames :: M.Map KernelName KernelSafety
                       , openClUsedTypes :: [PrimType]
                         -- ^ So we can detect whether the device is capable.
                       , openClSizes :: M.Map Name SizeClass
                         -- ^ Runtime-configurable constants.
                       , openClFailures :: [FailureMsg]
                         -- ^ Assertion failure error messages.
                       , hostDefinitions :: Definitions OpenCL
                       }

-- | Something that can go wrong in a kernel.  Part of the machinery
-- for reporting error messages from within kernels.
data FailureMsg = FailureMsg { failureError :: ErrorMsg Exp
                             , failureBacktrace :: String
                             }

-- | A function calling OpenCL kernels.
type Function = Imp.Function OpenCL

-- | A piece of code calling OpenCL.
type Code = Imp.Code OpenCL

-- | The name of a kernel.
type KernelName = Name

-- | An argument to be passed to a kernel.
data KernelArg = ValueKArg Exp PrimType
                 -- ^ Pass the value of this scalar expression as argument.
               | MemKArg VName
                 -- ^ Pass this pointer as argument.
               | SharedMemoryKArg (Count Bytes Exp)
                 -- ^ Create this much local memory per workgroup.
               deriving (Show)

-- | Whether a kernel can potentially fail (because it contains bounds
-- checks and such).
data MayFail = MayFail | CannotFail
             deriving (Show)

-- | Information about bounds checks and how sensitive it is to
-- errors.  Ordered by least demanding to most.
data KernelSafety
  = SafetyNone
    -- ^ Does not need to know if we are in a failing state, and also
    -- cannot fail.
  | SafetyCheap
    -- ^ Needs to be told if there's a global failure, and that's it,
    -- and cannot fail.
  | SafetyFull
    -- ^ Needs all parameters, may fail itself.
    deriving (Eq, Ord, Show)

-- | How many leading failure arguments we must pass when launching a
-- kernel with these safety characteristics.
numFailureParams :: KernelSafety -> Int
numFailureParams SafetyNone = 0
numFailureParams SafetyCheap = 1
numFailureParams SafetyFull = 3

-- | Host-level OpenCL operation.
data OpenCL = LaunchKernel KernelSafety KernelName [KernelArg] [Exp] [Exp]
            | GetSize VName Name
            | CmpSizeLe VName Name Exp
            | GetSizeMax VName SizeClass
            deriving (Show)

-- | The target platform when compiling imperative code to a 'Program'
data KernelTarget = TargetOpenCL
                  | TargetCUDA
                  deriving (Eq)

instance Pretty OpenCL where
  ppr = text . show