Ian Lance Taylor schrieb:
On Fri, Feb 8, 2013 at 10:15 AM, Grobman Alexander-R53196
<R53196@xxxxxxxxxxxxx> wrote:
I'm trying to incorporate new PPC instructions into a C code. These instructions use limited set of GPRs as operands i.e. only even registers can be used as a source,
Is there way to specify that in the asm() statement?
As far as I know there is no constraint that describes only the even
registers of the general register set. It would not be very difficult
to add one to the PPC backend. I can't think of any other way to
approach this.
AFAIK that does not work because the respective register class would
have holes. You cannot have a register class that contains only even
registers and omits the odd ones. Or can IRA / reload handle this now?
One way would be to use HARD_REGNO_MODE_OK and restrict 64-bit modes to
even registers, but that would be an ABI change...
From the C level a local register variable could be use, thus it is
possible to describe but the results will be suboptimal because the
respective operand is not available for register allocation.
Johann
