...Ok, and now with the patch attached...

Here is a revised version of the patch.  The difference to the
previous one is that it adds some combine patterns for *cbranch
insns that were lost in the PR92729 transition.  The post-reload
part of the patterns were still there.  The new patterns are
slightly more general in that they also handle fixed-point modes.

Apart from that, the patch behaves the same:

Am 15.05.23 um 20:05 schrieb Georg-Johann Lay:
> This patch fixes a wrong-code bug in the wake of PR92729, the transition
> that turned the AVR backend from cc0 to CCmode.  In cc0, the insn that
> uses cc0 like a conditional branch always follows the cc0 setter, which
> is no more the case with CCmode where set and use of REG_CC might be in
> different basic blocks.
> 
> This patch removes the machine-dependent reorg pass in avr_reorg entirely.
> 
> It is replaced by a new, AVR specific mini-pass that runs prior to
> split2. Canonicalization of comparisons away from the "difficult"
> codes GT[U] and LE[U] is now mostly performed by implementing
> TARGET_CANONICALIZE_COMPARISON.
> 
> Moreover:
> 
> * Text peephole conditions get "dead_or_set_regno_p (*, REG_CC)" as
> needed.
> 
> * RTL peephole conditions get "peep2_regno_dead_p (*, REG_CC)" as
> needed.
> 
> * Conditional branches no more clobber REG_CC.
> 
> * insn output for compares looks ahead to determine the branch mode in
> use. This needs also "dead_or_set_regno_p (*, REG_CC)".
> 
> * Add RTL peepholes for decrement-and-branch detection.
> 
> Finally, it fixes some of the many indentation glitches left over from
> PR92729.
> 
> Ok?
> 
> I'd also backport this one because all of v12+ is affected by the wrong 
> code.

Johann

--

gcc/
	PR target/109650
	PR target/92729

	* config/avr/avr-passes.def (avr_pass_ifelse): Insert new pass.
	* config/avr/avr.cc (avr_pass_ifelse): New RTL pass.
	(avr_pass_data_ifelse): New pass_data for it.
	(make_avr_pass_ifelse, avr_redundant_compare, avr_cbranch_cost)
	(avr_canonicalize_comparison, avr_out_plus_set_ZN)
	(avr_out_cmp_ext): New functions.
	(compare_condtition): Make sure REG_CC dies in the branch insn.
	(avr_rtx_costs_1): Add computation of cbranch costs.
	(avr_adjust_insn_length) [ADJUST_LEN_ADD_SET_ZN, ADJUST_LEN_CMP_ZEXT]:
	[ADJUST_LEN_CMP_SEXT]Handle them.
	(TARGET_CANONICALIZE_COMPARISON): New define.
	(avr_simplify_comparison_p, compare_diff_p, avr_compare_pattern)
	(avr_reorg_remove_redundant_compare, avr_reorg): Remove functions.
	(TARGET_MACHINE_DEPENDENT_REORG): Remove define.

	* avr-protos.h (avr_simplify_comparison_p): Remove proto.
	(make_avr_pass_ifelse, avr_out_plus_set_ZN, cc_reg_rtx)
	(avr_out_cmp_zext): New Protos

	* config/avr/avr.md (branch, difficult_branch): Don't split insns.
	(*cbranchhi.zero-extend.0", *cbranchhi.zero-extend.1")
	(*swapped_tst<mode>, *add.for.eqne.<mode>): New insns.
	(*cbranch<mode>4): Rename to cbranch<mode>4_insn.
	(define_peephole): Add dead_or_set_regno_p(insn,REG_CC) as needed.
	(define_deephole2): Add peep2_regno_dead_p(*,REG_CC) as needed.
	Add new RTL peepholes for decrement-and-branch and *swapped_tst<mode>.
	Rework signtest-and-branch peepholes for *sbrx_branch<mode>.
	(adjust_len) [add_set_ZN, cmp_zext]: New.
	(QIPSI): New mode iterator.
	(ALLs1, ALLs2, ALLs4, ALLs234): New mode iterators.
	(gelt): New code iterator.
	(gelt_eqne): New code attribute.
	(rvbranch, *rvbranch, difficult_rvbranch, *difficult_rvbranch)
	(branch_unspec, *negated_tst<mode>, *reversed_tst<mode>)
	(*cmpqi_sign_extend): Remove insns.
	(define_c_enum "unspec") [UNSPEC_IDENTITY]: Remove.

	* config/avr/avr-dimode.md (cbranch<mode>4): Canonicalize comparisons.
	* config/avr/predicates.md (scratch_or_d_register_operand): New.
	* config/avr/contraints.md (Yxx): New constraint.

gcc/testsuite/
	PR target/109650
	* config/avr/torture/pr109650-1.c: New test.
	* config/avr/torture/pr109650-2.c: New test.