{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE TupleSections #-}

-- | C code generation for whole programs, built on
-- "Futhark.CodeGen.Backends.GenericC.Monad".  Most of this module is
-- concerned with constructing the C API.
module Futhark.CodeGen.Backends.GenericC
  ( compileProg,
    compileProg',
    compileFun,
    defaultOperations,
    CParts (..),
    asLibrary,
    asExecutable,
    asServer,
    module Futhark.CodeGen.Backends.GenericC.Monad,
    module Futhark.CodeGen.Backends.GenericC.Code,
  )
where

import Control.Monad.Reader
import Control.Monad.State
import qualified Data.DList as DL
import Data.Loc
import qualified Data.Map.Strict as M
import Data.Maybe
import qualified Data.Text as T
import Futhark.CodeGen.Backends.GenericC.CLI (cliDefs)
import Futhark.CodeGen.Backends.GenericC.Code
import Futhark.CodeGen.Backends.GenericC.EntryPoints
import Futhark.CodeGen.Backends.GenericC.Monad
import Futhark.CodeGen.Backends.GenericC.Options
import Futhark.CodeGen.Backends.GenericC.Server (serverDefs)
import Futhark.CodeGen.Backends.GenericC.Types
import Futhark.CodeGen.ImpCode
import Futhark.CodeGen.RTS.C (cacheH, contextH, contextPrototypesH, errorsH, halfH, lockH, timingH, utilH)
import qualified Futhark.Manifest as Manifest
import Futhark.MonadFreshNames
import Futhark.Util.Pretty (prettyText)
import qualified Language.C.Quote.OpenCL as C
import qualified Language.C.Syntax as C
import NeatInterpolation (untrimming)

defCall :: CallCompiler op s
defCall dests fname args = do
  let out_args = [[C.cexp|&$id:d|] | d <- dests]
      args' = [C.cexp|ctx|] : out_args ++ args
  item [C.citem|if ($id:(funName fname)($args:args') != 0) { err = 1; goto cleanup; }|]

defError :: ErrorCompiler op s
defError msg stacktrace = do
  (formatstr, formatargs) <- errorMsgString msg
  let formatstr' = "Error: " <> formatstr <> "\n\nBacktrace:\n%s"
  items
    [C.citems|set_error(ctx, msgprintf($string:formatstr', $args:formatargs, $string:stacktrace));
              err = FUTHARK_PROGRAM_ERROR;
              goto cleanup;|]

-- | A set of operations that fail for every operation involving
-- non-default memory spaces.  Uses plain pointers and @malloc@ for
-- memory management.
defaultOperations :: Operations op s
defaultOperations =
  Operations
    { opsWriteScalar = defWriteScalar,
      opsReadScalar = defReadScalar,
      opsAllocate = defAllocate,
      opsDeallocate = defDeallocate,
      opsCopy = defCopy,
      opsStaticArray = defStaticArray,
      opsMemoryType = defMemoryType,
      opsCompiler = defCompiler,
      opsFatMemory = True,
      opsError = defError,
      opsCall = defCall,
      opsCritical = mempty
    }
  where
    defWriteScalar _ _ _ _ _ =
      error "Cannot write to non-default memory space because I am dumb"
    defReadScalar _ _ _ _ =
      error "Cannot read from non-default memory space"
    defAllocate _ _ _ =
      error "Cannot allocate in non-default memory space"
    defDeallocate _ _ =
      error "Cannot deallocate in non-default memory space"
    defCopy _ destmem destoffset DefaultSpace srcmem srcoffset DefaultSpace size =
      copyMemoryDefaultSpace destmem destoffset srcmem srcoffset size
    defCopy _ _ _ _ _ _ _ _ =
      error "Cannot copy to or from non-default memory space"
    defStaticArray _ _ _ _ =
      error "Cannot create static array in non-default memory space"
    defMemoryType _ =
      error "Has no type for non-default memory space"
    defCompiler _ =
      error "The default compiler cannot compile extended operations"

compileFunBody :: [C.Exp] -> [Param] -> Code op -> CompilerM op s ()
compileFunBody output_ptrs outputs code = do
  mapM_ declareOutput outputs
  compileCode code
  zipWithM_ setRetVal' output_ptrs outputs
  where
    declareOutput (MemParam name space) =
      declMem name space
    declareOutput (ScalarParam name pt) = do
      let ctp = primTypeToCType pt
      decl [C.cdecl|$ty:ctp $id:name;|]

    setRetVal' p (MemParam name space) = do
      resetMem [C.cexp|*$exp:p|] space
      setMem [C.cexp|*$exp:p|] name space
    setRetVal' p (ScalarParam name _) =
      stm [C.cstm|*$exp:p = $id:name;|]

compileFun :: [C.BlockItem] -> [C.Param] -> (Name, Function op) -> CompilerM op s (C.Definition, C.Func)
compileFun get_constants extra (fname, func@(Function _ outputs inputs body)) = inNewFunction $ do
  (outparams, out_ptrs) <- unzip <$> mapM compileOutput outputs
  inparams <- mapM compileInput inputs

  cachingMemory (lexicalMemoryUsage func) $ \decl_cached free_cached -> do
    body' <- collect $ compileFunBody out_ptrs outputs body
    decl_mem <- declAllocatedMem
    free_mem <- freeAllocatedMem

    pure
      ( [C.cedecl|static int $id:(funName fname)($params:extra, $params:outparams, $params:inparams);|],
        [C.cfun|static int $id:(funName fname)($params:extra, $params:outparams, $params:inparams) {
               $stms:ignores
               int err = 0;
               $items:decl_cached
               $items:decl_mem
               $items:get_constants
               $items:body'
              cleanup:
               {
               $stms:free_cached
               $items:free_mem
               }
               return err;
  }|]
      )
  where
    -- Ignore all the boilerplate parameters, just in case we don't
    -- actually need to use them.
    ignores = [[C.cstm|(void)$id:p;|] | C.Param (Just p) _ _ _ <- extra]

    compileInput (ScalarParam name bt) = do
      let ctp = primTypeToCType bt
      pure [C.cparam|$ty:ctp $id:name|]
    compileInput (MemParam name space) = do
      ty <- memToCType name space
      pure [C.cparam|$ty:ty $id:name|]

    compileOutput (ScalarParam name bt) = do
      let ctp = primTypeToCType bt
      p_name <- newVName $ "out_" ++ baseString name
      pure ([C.cparam|$ty:ctp *$id:p_name|], [C.cexp|$id:p_name|])
    compileOutput (MemParam name space) = do
      ty <- memToCType name space
      p_name <- newVName $ baseString name ++ "_p"
      pure ([C.cparam|$ty:ty *$id:p_name|], [C.cexp|$id:p_name|])

declsCode :: (HeaderSection -> Bool) -> CompilerState s -> T.Text
declsCode p =
  T.unlines
    . map prettyText
    . concatMap (DL.toList . snd)
    . filter (p . fst)
    . M.toList
    . compHeaderDecls

initDecls, arrayDecls, opaqueDecls, opaqueTypeDecls, entryDecls, miscDecls :: CompilerState s -> T.Text
initDecls = declsCode (== InitDecl)
arrayDecls = declsCode isArrayDecl
  where
    isArrayDecl ArrayDecl {} = True
    isArrayDecl _ = False
opaqueTypeDecls = declsCode isOpaqueTypeDecl
  where
    isOpaqueTypeDecl OpaqueTypeDecl {} = True
    isOpaqueTypeDecl _ = False
opaqueDecls = declsCode isOpaqueDecl
  where
    isOpaqueDecl OpaqueDecl {} = True
    isOpaqueDecl _ = False
entryDecls = declsCode (== EntryDecl)
miscDecls = declsCode (== MiscDecl)

defineMemorySpace :: Space -> CompilerM op s (C.Definition, [C.Definition], C.BlockItem)
defineMemorySpace space = do
  rm <- rawMemCType space
  let structdef =
        [C.cedecl|struct $id:sname { int *references;
                                     $ty:rm mem;
                                     typename int64_t size;
                                     const char *desc; };|]

  contextField peakname [C.cty|typename int64_t|] $ Just [C.cexp|0|]
  contextField usagename [C.cty|typename int64_t|] $ Just [C.cexp|0|]

  -- Unreferencing a memory block consists of decreasing its reference
  -- count and freeing the corresponding memory if the count reaches
  -- zero.
  free <- collect $ freeRawMem [C.cexp|block->mem|] space [C.cexp|desc|]
  ctx_ty <- contextType
  let unrefdef =
        [C.cedecl|int $id:(fatMemUnRef space) ($ty:ctx_ty *ctx, $ty:mty *block, const char *desc) {
  if (block->references != NULL) {
    *(block->references) -= 1;
    if (ctx->detail_memory) {
      fprintf(ctx->log, "Unreferencing block %s (allocated as %s) in %s: %d references remaining.\n",
                      desc, block->desc, $string:spacedesc, *(block->references));
    }
    if (*(block->references) == 0) {
      ctx->$id:usagename -= block->size;
      $items:free
      free(block->references);
      if (ctx->detail_memory) {
        fprintf(ctx->log, "%lld bytes freed (now allocated: %lld bytes)\n",
                (long long) block->size, (long long) ctx->$id:usagename);
      }
    }
    block->references = NULL;
  }
  return 0;
}|]

  -- When allocating a memory block we initialise the reference count to 1.
  alloc <-
    collect $
      allocRawMem [C.cexp|block->mem|] [C.cexp|size|] space [C.cexp|desc|]
  let allocdef =
        [C.cedecl|int $id:(fatMemAlloc space) ($ty:ctx_ty *ctx, $ty:mty *block, typename int64_t size, const char *desc) {
  if (size < 0) {
    futhark_panic(1, "Negative allocation of %lld bytes attempted for %s in %s.\n",
          (long long)size, desc, $string:spacedesc, ctx->$id:usagename);
  }
  int ret = $id:(fatMemUnRef space)(ctx, block, desc);

  if (ret != FUTHARK_SUCCESS) {
    return ret;
  }

  if (ctx->detail_memory) {
    fprintf(ctx->log, "Allocating %lld bytes for %s in %s (then allocated: %lld bytes)",
            (long long) size,
            desc, $string:spacedesc,
            (long long) ctx->$id:usagename + size);
  }
  if (ctx->$id:usagename > ctx->$id:peakname) {
    ctx->$id:peakname = ctx->$id:usagename;
    if (ctx->detail_memory) {
      fprintf(ctx->log, " (new peak).\n");
    }
  } else if (ctx->detail_memory) {
    fprintf(ctx->log, ".\n");
  }

  $items:alloc

  if (ctx->error == NULL) {
    block->references = (int*) malloc(sizeof(int));
    *(block->references) = 1;
    block->size = size;
    block->desc = desc;
    ctx->$id:usagename += size;
    return FUTHARK_SUCCESS;
  } else {
    // We are naively assuming that any memory allocation error is due to OOM.
    // We preserve the original error so that a savvy user can perhaps find
    // glory despite our naiveté.

    // We cannot use set_error() here because we want to replace the old error.
    lock_lock(&ctx->error_lock);
    char *old_error = ctx->error;
    ctx->error = msgprintf("Failed to allocate memory in %s.\nAttempted allocation: %12lld bytes\nCurrently allocated:  %12lld bytes\n%s",
                           $string:spacedesc,
                           (long long) size,
                           (long long) ctx->$id:usagename,
                           old_error);
    free(old_error);
    lock_unlock(&ctx->error_lock);
    return FUTHARK_OUT_OF_MEMORY;
  }
  }|]

  -- Memory setting - unreference the destination and increase the
  -- count of the source by one.
  let setdef =
        [C.cedecl|int $id:(fatMemSet space) ($ty:ctx_ty *ctx, $ty:mty *lhs, $ty:mty *rhs, const char *lhs_desc) {
  int ret = $id:(fatMemUnRef space)(ctx, lhs, lhs_desc);
  if (rhs->references != NULL) {
    (*(rhs->references))++;
  }
  *lhs = *rhs;
  return ret;
}
|]

  onClear [C.citem|ctx->$id:peakname = 0;|]

  let peakmsg = "Peak memory usage for " ++ spacedesc ++ ": %lld bytes.\n"
  pure
    ( structdef,
      [unrefdef, allocdef, setdef],
      -- Do not report memory usage for DefaultSpace (CPU memory),
      -- because it would not be accurate anyway.  This whole
      -- tracking probably needs to be rethought.
      if space == DefaultSpace
        then [C.citem|{}|]
        else [C.citem|str_builder(&builder, $string:peakmsg, (long long) ctx->$id:peakname);|]
    )
  where
    mty = fatMemType space
    (peakname, usagename, sname, spacedesc) = case space of
      Space sid ->
        ( C.toIdent ("peak_mem_usage_" ++ sid) noLoc,
          C.toIdent ("cur_mem_usage_" ++ sid) noLoc,
          C.toIdent ("memblock_" ++ sid) noLoc,
          "space '" ++ sid ++ "'"
        )
      _ ->
        ( "peak_mem_usage_default",
          "cur_mem_usage_default",
          "memblock",
          "default space"
        )

-- | The result of compilation to C is multiple parts, which can be
-- put together in various ways.  The obvious way is to concatenate
-- all of them, which yields a CLI program.  Another is to compile the
-- library part by itself, and use the header file to call into it.
data CParts = CParts
  { cHeader :: T.Text,
    -- | Utility definitions that must be visible
    -- to both CLI and library parts.
    cUtils :: T.Text,
    cCLI :: T.Text,
    cServer :: T.Text,
    cLib :: T.Text,
    -- | The manifest, in JSON format.
    cJsonManifest :: T.Text
  }

gnuSource :: T.Text
gnuSource =
  [untrimming|
// We need to define _GNU_SOURCE before
// _any_ headers files are imported to get
// the usage statistics of a thread (i.e. have RUSAGE_THREAD) on GNU/Linux
// https://manpages.courier-mta.org/htmlman2/getrusage.2.html
#ifndef _GNU_SOURCE // Avoid possible double-definition warning.
#define _GNU_SOURCE
#endif
|]

-- We may generate variables that are never used (e.g. for
-- certificates) or functions that are never called (e.g. unused
-- intrinsics), and generated code may have other cosmetic issues that
-- compilers warn about.  We disable these warnings to not clutter the
-- compilation logs.
disableWarnings :: T.Text
disableWarnings =
  [untrimming|
#ifdef __clang__
#pragma clang diagnostic ignored "-Wunused-function"
#pragma clang diagnostic ignored "-Wunused-variable"
#pragma clang diagnostic ignored "-Wparentheses"
#pragma clang diagnostic ignored "-Wunused-label"
#elif __GNUC__
#pragma GCC diagnostic ignored "-Wunused-function"
#pragma GCC diagnostic ignored "-Wunused-variable"
#pragma GCC diagnostic ignored "-Wparentheses"
#pragma GCC diagnostic ignored "-Wunused-label"
#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
#endif
|]

-- | Produce header, implementation, and manifest files.
asLibrary :: CParts -> (T.Text, T.Text, T.Text)
asLibrary parts =
  ( "#pragma once\n\n" <> cHeader parts,
    gnuSource <> disableWarnings <> cHeader parts <> cUtils parts <> cLib parts,
    cJsonManifest parts
  )

-- | As executable with command-line interface.
asExecutable :: CParts -> T.Text
asExecutable parts =
  gnuSource <> disableWarnings <> cHeader parts <> cUtils parts <> cCLI parts <> cLib parts

-- | As server executable.
asServer :: CParts -> T.Text
asServer parts =
  gnuSource <> disableWarnings <> cHeader parts <> cUtils parts <> cServer parts <> cLib parts

compileProg' ::
  MonadFreshNames m =>
  T.Text ->
  T.Text ->
  Operations op s ->
  s ->
  CompilerM op s () ->
  T.Text ->
  (Space, [Space]) ->
  [Option] ->
  Definitions op ->
  m (CParts, CompilerState s)
compileProg' backend version ops def extra header_extra (arr_space, spaces) options prog = do
  src <- getNameSource
  let ((prototypes, definitions, entry_point_decls, manifest), endstate) =
        runCompilerM ops src def compileProgAction
      initdecls = initDecls endstate
      entrydecls = entryDecls endstate
      arraydecls = arrayDecls endstate
      opaquetypedecls = opaqueTypeDecls endstate
      opaquedecls = opaqueDecls endstate
      miscdecls = miscDecls endstate

  let headerdefs =
        [untrimming|
// Headers
#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#include <stdio.h>
#include <float.h>
$header_extra
#ifdef __cplusplus
extern "C" {
#endif

// Initialisation
$initdecls

// Arrays
$arraydecls

// Opaque values
$opaquetypedecls
$opaquedecls

// Entry points
$entrydecls

// Miscellaneous
$miscdecls
#define FUTHARK_BACKEND_$backend
$errorsH

#ifdef __cplusplus
}
#endif
|]

  let utildefs =
        [untrimming|
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include <stdint.h>
// If NDEBUG is set, the assert() macro will do nothing. Since Futhark
// (unfortunately) makes use of assert() for error detection (and even some
// side effects), we want to avoid that.
#undef NDEBUG
#include <assert.h>
#include <stdarg.h>
$utilH
$cacheH
$halfH
$timingH
|]

  let early_decls = T.unlines $ map prettyText $ DL.toList $ compEarlyDecls endstate
      lib_decls = T.unlines $ map prettyText $ DL.toList $ compLibDecls endstate
      clidefs = cliDefs options manifest
      serverdefs = serverDefs options manifest
      libdefs =
        [untrimming|
#ifdef _MSC_VER
#define inline __inline
#endif
#include <string.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <ctype.h>

$header_extra

$lockH

#define FUTHARK_F64_ENABLED

$cScalarDefs

$contextPrototypesH

$early_decls

$contextH

$prototypes

$lib_decls

$definitions

$entry_point_decls
  |]

  pure
    ( CParts
        { cHeader = headerdefs,
          cUtils = utildefs,
          cCLI = clidefs,
          cServer = serverdefs,
          cLib = libdefs,
          cJsonManifest = Manifest.manifestToJSON manifest
        },
      endstate
    )
  where
    Definitions types consts (Functions funs) = prog

    compileProgAction = do
      (memstructs, memfuns, memreport) <- unzip3 <$> mapM defineMemorySpace spaces

      get_consts <- compileConstants consts

      ctx_ty <- contextType

      (prototypes, functions) <-
        unzip <$> mapM (compileFun get_consts [[C.cparam|$ty:ctx_ty *ctx|]]) funs

      mapM_ earlyDecl memstructs
      (entry_points, entry_points_manifest) <-
        unzip . catMaybes <$> mapM (uncurry (onEntryPoint get_consts)) funs

      extra

      mapM_ earlyDecl $ concat memfuns

      type_funs <- generateAPITypes arr_space types
      generateCommonLibFuns memreport

      pure
        ( T.unlines $ map prettyText prototypes,
          T.unlines $ map (prettyText . funcToDef) functions,
          T.unlines $ map prettyText entry_points,
          Manifest.Manifest (M.fromList entry_points_manifest) type_funs backend version
        )

    funcToDef func = C.FuncDef func loc
      where
        loc = case func of
          C.OldFunc _ _ _ _ _ _ l -> l
          C.Func _ _ _ _ _ l -> l

-- | Compile imperative program to a C program.  Always uses the
-- function named "main" as entry point, so make sure it is defined.
compileProg ::
  MonadFreshNames m =>
  T.Text ->
  T.Text ->
  Operations op () ->
  CompilerM op () () ->
  T.Text ->
  (Space, [Space]) ->
  [Option] ->
  Definitions op ->
  m CParts
compileProg backend version ops extra header_extra (arr_space, spaces) options prog =
  fst <$> compileProg' backend version ops () extra header_extra (arr_space, spaces) options prog

generateCommonLibFuns :: [C.BlockItem] -> CompilerM op s ()
generateCommonLibFuns memreport = do
  ctx <- contextType
  cfg <- configType
  ops <- asks envOperations
  profilereport <- gets $ DL.toList . compProfileItems

  publicDef_ "context_config_set_cache_file" MiscDecl $ \s ->
    ( [C.cedecl|void $id:s($ty:cfg* cfg, const char *f);|],
      [C.cedecl|void $id:s($ty:cfg* cfg, const char *f) {
                 cfg->cache_fname = f;
               }|]
    )

  publicDef_ "get_tuning_param_count" InitDecl $ \s ->
    ( [C.cedecl|int $id:s(void);|],
      [C.cedecl|int $id:s(void) {
                return sizeof(tuning_param_names)/sizeof(tuning_param_names[0]);
              }|]
    )

  publicDef_ "get_tuning_param_name" InitDecl $ \s ->
    ( [C.cedecl|const char* $id:s(int);|],
      [C.cedecl|const char* $id:s(int i) {
                return tuning_param_names[i];
              }|]
    )

  publicDef_ "get_tuning_param_class" InitDecl $ \s ->
    ( [C.cedecl|const char* $id:s(int);|],
      [C.cedecl|const char* $id:s(int i) {
                return tuning_param_classes[i];
              }|]
    )

  sync <- publicName "context_sync"
  publicDef_ "context_report" MiscDecl $ \s ->
    ( [C.cedecl|char* $id:s($ty:ctx *ctx);|],
      [C.cedecl|char* $id:s($ty:ctx *ctx) {
                 if ($id:sync(ctx) != 0) {
                   return NULL;
                 }

                 struct str_builder builder;
                 str_builder_init(&builder);
                 $items:memreport
                 if (ctx->profiling) {
                   $items:profilereport
                 }
                 return builder.str;
               }|]
    )

  publicDef_ "context_get_error" MiscDecl $ \s ->
    ( [C.cedecl|char* $id:s($ty:ctx* ctx);|],
      [C.cedecl|char* $id:s($ty:ctx* ctx) {
                         char* error = ctx->error;
                         ctx->error = NULL;
                         return error;
                       }|]
    )

  publicDef_ "context_set_logging_file" MiscDecl $ \s ->
    ( [C.cedecl|void $id:s($ty:ctx* ctx, typename FILE* f);|],
      [C.cedecl|void $id:s($ty:ctx* ctx, typename FILE* f) {
                  ctx->log = f;
                }|]
    )

  publicDef_ "context_pause_profiling" MiscDecl $ \s ->
    ( [C.cedecl|void $id:s($ty:ctx* ctx);|],
      [C.cedecl|void $id:s($ty:ctx* ctx) {
                 ctx->profiling_paused = 1;
               }|]
    )

  publicDef_ "context_unpause_profiling" MiscDecl $ \s ->
    ( [C.cedecl|void $id:s($ty:ctx* ctx);|],
      [C.cedecl|void $id:s($ty:ctx* ctx) {
                 ctx->profiling_paused = 0;
               }|]
    )

  clears <- gets $ DL.toList . compClearItems
  publicDef_ "context_clear_caches" MiscDecl $ \s ->
    ( [C.cedecl|int $id:s($ty:ctx* ctx);|],
      [C.cedecl|int $id:s($ty:ctx* ctx) {
                         $items:(criticalSection ops clears)
                         return ctx->error != NULL;
                       }|]
    )

compileConstants :: Constants op -> CompilerM op s [C.BlockItem]
compileConstants (Constants ps init_consts) = do
  ctx_ty <- contextType
  const_fields <- mapM constParamField ps
  -- Avoid an empty struct, as that is apparently undefined behaviour.
  let const_fields'
        | null const_fields = [[C.csdecl|int dummy;|]]
        | otherwise = const_fields
  contextField "constants" [C.cty|struct { $sdecls:const_fields' }|] Nothing
  earlyDecl [C.cedecl|static int init_constants($ty:ctx_ty*);|]
  earlyDecl [C.cedecl|static int free_constants($ty:ctx_ty*);|]

  inNewFunction $ do
    -- We locally define macros for the constants, so that when we
    -- generate assignments to local variables, we actually assign into
    -- the constants struct.  This is not needed for functions, because
    -- they can only read constants, not write them.
    let (defs, undefs) = unzip $ map constMacro ps
    init_consts' <- collect $ do
      mapM_ resetMemConst ps
      compileCode init_consts
    decl_mem <- declAllocatedMem
    free_mem <- freeAllocatedMem
    libDecl
      [C.cedecl|static int init_constants($ty:ctx_ty *ctx) {
        (void)ctx;
        int err = 0;
        $items:defs
        $items:decl_mem
        $items:init_consts'
        $items:free_mem
        $items:undefs
        cleanup:
        return err;
      }|]

  inNewFunction $ do
    free_consts <- collect $ mapM_ freeConst ps
    libDecl
      [C.cedecl|static int free_constants($ty:ctx_ty *ctx) {
        (void)ctx;
        $items:free_consts
        return 0;
      }|]

  mapM getConst ps
  where
    constParamField (ScalarParam name bt) = do
      let ctp = primTypeToCType bt
      pure [C.csdecl|$ty:ctp $id:name;|]
    constParamField (MemParam name space) = do
      ty <- memToCType name space
      pure [C.csdecl|$ty:ty $id:name;|]

    constMacro p = ([C.citem|$escstm:def|], [C.citem|$escstm:undef|])
      where
        p' = pretty (C.toIdent (paramName p) mempty)
        def = "#define " ++ p' ++ " (" ++ "ctx->constants." ++ p' ++ ")"
        undef = "#undef " ++ p'

    resetMemConst ScalarParam {} = pure ()
    resetMemConst (MemParam name space) = resetMem name space

    freeConst ScalarParam {} = pure ()
    freeConst (MemParam name space) = unRefMem [C.cexp|ctx->constants.$id:name|] space

    getConst (ScalarParam name bt) = do
      let ctp = primTypeToCType bt
      pure [C.citem|$ty:ctp $id:name = ctx->constants.$id:name;|]
    getConst (MemParam name space) = do
      ty <- memToCType name space
      pure [C.citem|$ty:ty $id:name = ctx->constants.$id:name;|]