CmmLint error when doing safe ccall from cmm

[Simon Peyton Jones]

I'm not following this thread, but is it worth a ticket?  Or better user manual documentation?  Or something?

Simon

| -----Original Message-----
| From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of Simon
| Marlow
| Sent: 20 June 2014 21:25
| To: Yuras Shumovich; ghc-devs at haskell.org
| Subject: Re: CmmLint error when doing safe ccall from cmm
| 
| On 20/06/14 15:03, Yuras Shumovich wrote:
| > 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
| 
| I believe we only support 64-bit results on a 64-bit platform, but we
| you can always narrow to 32 bits with an MO_Conv afterwards if you want.
|   This is essentially what happens when you call a function that returns
| CInt using the FFI - you can always try that and see what Cmm you get.
| 
| Also, I'll be mildly surprised if using safe foreign calls from hand-
| written Cmm works, since I don't believe we use them anywhere so it
| isn't likely to be well tested :-)
| 
| Cheers,
| Simon
| 
| 
| > 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
| >
| >
| > _______________________________________________
| > ghc-devs mailing list
| > ghc-devs at haskell.org
| > http://www.haskell.org/mailman/listinfo/ghc-devs
| >
| 
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