CmmLint error when doing safe ccall from cmm

[Yuras Shumovich]

Simon,

Sorry if I'm too stupid, but
do you mean we only support 64-bit results from "prim" call? But I'm
using TO_W_ macro to convert the result to 64-bit value before returning
from cmm function.
Or you mean result from "ccall" call?
nativeGen/X86/CodeGen.hs:genCCall64 definitely supports that. And it
works for unsafe "ccall".
Looks like the issue is somewhere in translation from high level cmm to
low level cmm.

Thanks,
Yuras

On Fri, 2014-06-20 at 21:24 +0100, Simon Marlow wrote:
> 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
> >
> >
> > _______________________________________________
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> >
>