CmmLint error when doing safe ccall from cmm

[Yuras Shumovich]

Hello,

I'm trying to do safe ccall from cmm (see below for the code). It seems
to work, but -dcmm-lint is not satisfied:

/opt/ghc-7.8.2/bin/ghc --make -o test hs.hs cmm.cmm c.c -dcmm-lint -fforce-recomp
Cmm lint error:
  in basic block c4
    in assignment: 
      _c1::I32 = R1;
      Reg ty: I32
      Rhs ty: I64
Program was:
  {offset
    c5: _c0::I64 = R1;
        _c2::I64 = c_test;
        _c3::I32 = %MO_UU_Conv_W64_W32(_c0::I64);
        I64[(young<c4> + 8)] = c4;
        foreign call "ccall" arg hints:  []  result hints:  [] (_c2::I64)(...) returns to c4 args: ([_c3::I32]) ress: ([_c1::I32])ret_args: 8ret_off: 8;
    c4: _c1::I32 = R1;
        R1 = %MO_SS_Conv_W32_W64(_c1::I32);
        call (P64[(old + 8)])(R1) args: 8, res: 0, upd: 8;
  }

<no location info>: 
Compilation had errors


The same code without "safe" annotation passes cmm lint. Is it my error
or ghc bug? How can I do safe ccall in cmm correctly?

Here is the code:

== c.c ==
#include <assert.h>

int c_test(int i)
{
  assert(i == 1);
  return 2;
}

== cmm.cmm
#include "Cmm.h"

cmm_test(W_ i)
{
  CInt i1;
  (i1) = ccall c_test(W_TO_INT(i)) "safe";
  return (TO_W_(i1));
}

== hs.hs ==
{-# LANGUAGE GHCForeignImportPrim #-}
{-# LANGUAGE ForeignFunctionInterface #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE UnboxedTuples #-}
{-# LANGUAGE UnliftedFFITypes #-}

import GHC.Prim
import GHC.Types
import Control.Exception

foreign import prim "cmm_test" test :: Int# -> Int#

main :: IO ()
main = do
  let i1 = test 1#
  assert (I# i1 == 2) (return ())


Thanks,
Yuras