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Re: condition codes, haifa-sched and virtual-stack-vars
- From: Richard Henderson <rth at redhat dot com>
- To: Greg McGary <greg at mcgary dot org>
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 30 Jan 2002 17:07:32 -0800
- Subject: Re: condition codes, haifa-sched and virtual-stack-vars
- References: <200201301859.g0UIxx606426@kayak.mcgary.org>
On Wed, Jan 30, 2002 at 11:59:59AM -0700, Greg McGary wrote:
> Later, global-reg alloc instantiates virtual-stack-vars as an
> offset from FP, so the move mutates into an add of fp+offset,
> clobbering the condition codes computed earlier in the bitfield test.
If you don't have a form of add that doesn't clobber condition
codes, you are screwed. Reload absolutely relies on the existance
of such an instruction.
Your only hope is to represent compare+branch as a single insn
until after reload.
r~