[cfe-dev] [llvm-dev] How to debug if LTO generate wrong code?

[Shi, Steven via cfe-dev]

Yes, the "normal" code model you mentioned is the small code model, which use RIP-relative addressing, but my firmware need large code model which can reside anywhere in the full 64-bit address space. So, I need LLVM LTO support large code model. 

Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522
iNet: 821-6522

> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Joerg
> Sonnenberger via llvm-dev
> Sent: Monday, May 30, 2016 6:18 PM
> To: llvm-dev at lists.llvm.org
> Subject: Re: [llvm-dev] [cfe-dev] How to debug if LTO generate wrong code?
> 
> On Mon, May 30, 2016 at 02:12:09AM +0000, Shi, Steven via llvm-dev wrote:
> > Hi Joerg,
> > My firmware case is I need load my firmware to run in high address
> > which is hardware required. It is not that my firmware really need
> > large static data and text code. My firmware modules are shared library
> > (like a DLL) built with "-fpic", and firmware loader will load them to
> > high address (larger than 2GB). I think this need is quite common to
> > system software, like firmware, driver and kernel mode code.
> 
> It sounds more like there a confusion about what symbols are internal
> and what not. The normal code model on AMD64 requires code and data to
> fit into 2GB, but non-local symbols are accessed indirectly. That
> doesn't happen in your case. For functions, that's normally partially
> the job of the linker (via stubs), but for data the compiler has to be
> aware of it. The load address is irrelevant for PIC.
> 
> Joerg
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