On 2011/5/13 04:26 PM, Richard Sandiford wrote:
> Richard Sandiford <richard.sandif...@linaro.org> writes:
>> Chung-Lin Tang <clt...@codesourcery.com> writes:
>>> My fix here simply adds 'reload_completed' as an additional condition
>>> for EPILOGUE_USES to return true for LR_REGNUM. I think this should be
>>> valid, as correct LR save/restoring is handled by the epilogue/prologue
>>> code; it should be safe for IRA to treat it as a normal call-used register.
>>
>> FWIW, epilogue_completed might be a more accurate choice.
>
> I still stand by this, although I realise no other target does it.
Did a re-test of the patch just to be sure, as expected the test results
were also clear. Attached is the updated patch.
>> It seems a lot of other ports suffer from the same problem though.
>> I wonder which targets really do want to make a register live throughout
>> the function? If none do, perhaps we should say that this macro is
>> only meaningful once the epilogue has been generated.
>
> To answer my own question, I suppose VRSAVE is one. So I was wrong
> about the target-independent "fix".
>
> Richard
To rehash what I remember we discussed at LDS, such registers like
VRSAVE might be more appropriately placed in global regs. It looks like
EPILOGUE_USES could be more clarified in its use...
To Richard Earnshaw and Ramana, is the patch okay for trunk? This should
be a not-so-insignificant performance regression-fix/improvement.
Thanks,
Chung-Lin
Index: config/arm/arm.h
===================================================================
--- config/arm/arm.h (revision 173814)
+++ config/arm/arm.h (working copy)
@@ -1627,7 +1627,7 @@
frame. */
#define EXIT_IGNORE_STACK 1
-#define EPILOGUE_USES(REGNO) ((REGNO) == LR_REGNUM)
+#define EPILOGUE_USES(REGNO) (epilogue_completed && (REGNO) == LR_REGNUM)
/* Determine if the epilogue should be output as RTL.
You should override this if you define FUNCTION_EXTRA_EPILOGUE. */
