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Re: [RFC][PR89245] Check REG_CALL_DECL note during the tail-merging

Dragan Mladjenovic <> writes:
> From: "Dragan Mladjenovic" <>
> This patch prevents merging of CALL instructions that that have different
> REG_CALL_DECL notes attached to them.
> On most architectures this is not an important distinction. Usually instruction patterns
> for calls to different functions reference different SYMBOL_REF-s, so they won't match.
> On MIPS PIC calls get split into an got_load/*call_internal pair where the latter represents
> indirect register call w/o SYMBOL_REF attached (until machine_reorg pass). The bugzilla issue
> had such two internal_call-s merged despite the fact that they had different register usage
> information assigned by ipa-ra.
> The check could be improved by checking if ipa-ra has actually assigned two different
> register sets for two functions involved, but I chose to only do a quick rtx_equal check.

Yeah, I think doing it that would be better (and maybe simpler?).
It should just be a case of:

	  get_call_reg_set_usage (i1, &i1_used_regs, call_used_reg_set);
	  get_call_reg_set_usage (i2, &i2_used_regs, call_used_reg_set);

and then checking that i1_used_regs and i2_used_regs are equal.


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