[PATCH] Generate SEH unwinding info on Win64

[Vadim Chugunov]

>>! In D4081#16, @loladiro wrote:
> I went and tried this out but ran into an assertion. This is odd because at that stage I wasn't actually using COFF, but rather ELF in memory for MCJIT. Maybe there's a check missing whether we are using COFF in addition to Win64? See below:
> 
> 
>   Program: C:\mingw-builds\msys64\home\kfischer\julia\usr\bin\julia.exe
>   File: C:/mingw-builds/msys64/home/kfischer/julia/deps/llvm-svn/lib/CodeGen/MachineInstr.cpp, Line 674
>   
>   Expression: (isImpReg || Op.isRegMask() || MCID->isVariadic() || OpNo < MCID->getNumOperands() || isMetaDataOp) && "Trying to add an operand to a machine instr that is already done!"
>   

Did you do a clean build?   I ran into something similar after adding SEH instructions, and the solution was to delete all .o and .inc files under Target\X86.   Apparently make dependencies are not quite reliable.

http://reviews.llvm.org/D4081