[PATCH 04/25] SPECIAL_REGNO_P

[Andrew Stubbs]

On 13/09/18 15:49, Paul Koning wrote:
> It's ambiguous, because the last sentence of that paragraph says "addm3 is used if addptrm3 is not defined."

I didn't read that as ambiguous; I read it as addm3 is assumed to work 
fine when addptr is not defined.

> I don't know of any change in this area.  All I know is that pdp11 has adds that clobber CC and it doesn't define addptrm3, relying on that last sentence.  I've tried LRA and for the most part it compiles successfully, I suppose I should verify the generated code based on the point you raised.  If I really have to define addptr, I'm in trouble because  save/restore CC is not easy on pdp11.

The code was added because we had a number of testcases that failed at 
runtime without it.

Admittedly, that was in a GCC 7 code-base, and I can't reproduce the 
failure with one of those test cases now (with addptr deleted), but 
possibly that's just noise.

Andrew