Re: New codegen failing test-cases

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 0x0804aa76 <+10>: add $0x4,%ebp 0x0804aa79 <+13>: add $0x8,%edi 0x0804aa7c <+16>: cmp 0x5c(%ebx),%edi 0x0804aa7f <+19>: ja 0x804aaa4 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