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Re: need help for GCC--RTL
- From: Ian Lance Taylor <iant at google dot com>
- To: Klaus Friedrich <klaus-fried at gmx dot net>
- Cc: gcc-help at gcc dot gnu dot org
- Date: 23 Mar 2007 09:26:41 -0700
- Subject: Re: need help for GCC--RTL
- References: <4603D278.8050205@gmx.net>
Klaus Friedrich <klaus-fried@gmx.net> writes:
> For my diploma thesis, i will work with the gcc4.1 internals. I would
> like to extract information about the RTL
> language. I search for a description of the virtual machine/virtual
> processor on the RTL instruction set and for example the register
> management/alignment.
>
> I can't find exakt information about the meaning for the RTL
> constructs. For Example the meaning for this reg expression [D.1281] in
> (reg:SI 58 [D.1281]) or the meaning for virtual-stack-vars in
> (reg/f:SI 54 virtual-stack-vars).
The [D.1281] refers to the variable associated with that register. In
this case I can tell by the name that it is a GIMPLE temporary
register. If you use -fdump-tree-final_cleanup and look in the dump
file you will see the last GIMPLE code before the expansion into RTL.
You should see D.1281 in that code.
virtual-stack-vars is a pseudo register which points to the first
local variable on the stack frame. It is only used for a little
while, and is eliminated by pass_instantiate_virtual_regs.
> I also information about the (clobber (reg:CC 17 flags)) expr. What do
> the clobber function with the reg 17 ?
What can I say: it clobbers it. See the RTL documentation.
Ian