New codegen failing test-cases

[Simon Marlow]

I think the bug might be here:

inlineStmt u a (CmmCall target regs es srt ret)
    = CmmCall (infn target) regs es' srt ret
    where infn (CmmCallee fn cconv) = CmmCallee fn cconv
	 infn (CmmPrim p) = CmmPrim p
	 es' = [ (CmmHinted (inlineExpr u a e) hint) | (CmmHinted e hint) <- es

(from cmm/CmmOpt.hs)  Note that it isn't substituting inside the 'fn' 
argument to CmmCallee, and it should be.  This bug has been around for ages.

Cheers,
	Simon

On 13/01/2011 04:34, Edward Z. Yang wrote:
> With further poking, I think the new codegen is actually tickling
> an existing bug in the native code generator optimizations, since
> the cmmz output looks ok:
>
>        cSH:
>            _sQR::I32 = I32[_sRi::I32 + 3];   // CmmAssign
>            _sQS::I32 = I32[_sRi::I32 + 7];   // CmmAssign
>            _sQT::I32 = I32[_sRi::I32 + 11];   // CmmAssign
>            _sQU::I32 = I32[_sRi::I32 + 15];   // CmmAssign
>            (_sR1::I32) = call "ccall" arg hints:  [`signed',
>                                                    PtrHint,]  result hints:  [] (_sQR::I32&  (-4))(_sQS::I32, _sQT::I32, _sQU::I32);   // CmmUnsafeForeignCall
>
> And the only change is that in the original code generator,
> the assignment to _sQR is elided.
>
>           _cSn::I32 = I32[R1 + 7];
>           _cSp::I32 = I32[R1 + 11];
>           _cSr::I32 = I32[R1 + 15];
>           (_sR1::I32,) = foreign "ccall"
>             I32[R1 + 3]((_cSn::I32, `signed'), (_cSp::I32, PtrHint),
>                         (_cSr::I32,))[_unsafe_call_];
>
> I further verified that there was no problem if I used -fvia-C.
> On closer inspection, the fact that _sQR is referenced nowhere
> in this dump should have raised alarms (I think the register
> allocater happened to assign it to the same register as
> _sRi, which is why the assembly looked vaguely plausible.)
>
> I'm still not sure where a fix might lie, but if I take another
> crack at it tomorrow I will probably figure it out.
>
> Cheers,
> Edward
>
> Excerpts from Edward Z. Yang's message of Wed Jan 12 17:10:11 -0500 2011:
>> I appear to have tracked down the bug for ffi021:  the new
>> code generator doesn't appear to clear the tag bit for the
>> pointer to heap before:
>>
>>          // outOfLine should follow:
>>          (_sR1::I32,) = foreign "ccall"
>>            _sQR::I32((I32[_sRi::I32 + 7], `signed'),
>>                      (I32[_sRi::I32 + 11], PtrHint),
>>                      (I32[_sRi::I32 + 15],))[_unsafe_call_];
>>          // emitReturn: Sequel: Assign
>>          ;
>>
>> (gdb) disas
>> Dump of assembler code for function sRi_info:
>> =>  0x0804aa6c<+0>:     mov    %esi,%eax
>>     0x0804aa6e<+2>:     lea    0x0(%ebp),%ecx
>>     0x0804aa71<+5>:     cmp    0x54(%ebx),%ecx
>>     0x0804aa74<+8>:     jb     0x804aab3<sRi_info+71>
>>     0x0804aa76<+10>:    add    $0x4,%ebp
>>     0x0804aa79<+13>:    add    $0x8,%edi
>>     0x0804aa7c<+16>:    cmp    0x5c(%ebx),%edi
>>     0x0804aa7f<+19>:    ja     0x804aaa4<sRi_info+56>
>>     0x0804aa81<+21>:    pushl  0xf(%eax)
>>     0x0804aa84<+24>:    pushl  0xb(%eax)
>>     0x0804aa87<+27>:    pushl  0x7(%eax)
>>     0x0804aa8a<+30>:    call   *%eax
>>
>> The pushes to the stack properly untag eax, but then we just
>> call the tagged pointer, which seems pretty wrong to me. Here is
>> the old C--:
>>
>>          (_sR1::I32,) = foreign "ccall"
>>            I32[R1 + 3]((_cSc::I32, `signed'), (_cSe::I32, PtrHint),
>>                        (_cSg::I32,))[_unsafe_call_];
>>
>> Unfortunately, I can't figure out where this +3 is supposed to
>> be happening, so I don't have a patch. Some guidance here would
>> be appreciated.
>>
>> Cheers,
>> Edward
>
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