On Tue, Feb 15, 2011 at 2:55 PM, Bernd Schmidt <ber...@codesourcery.com> wrote: > On 02/14/2011 08:46 PM, Eric Botcazou wrote: >>> I agree with Jeff that combine would be the correct place to fix this. >>> At least it takes class_likely_spilled_p into account, so it will >>> restrict only those machines where extending the lifetime of hard regs >>> is dangerous. >> >> OK, but I don't see how copying to a new pseudo would interfere with that. > > For one thing, the set no longer matches the REG_EQUIV note we make > here, and that does seem to interfere with the optimization. I've tested > both patches on ARM, -march=armv7-a. The combiner patch produced no code > changes. The function.c patch produced regressions (increased register > pressure). Both results are as expected. > > To put it another way: the combiner change is conservatively correct, > and necessary if we're going to have extends of hard registers in the > RTL. The function.c change is demonstrably incorrect as shown by the ARM > codegen regressions. >
I checked in my patch into trunk. Thanks. -- H.J.
