Re: [PATCH v4 4/5] RISC-V: Add macro-fusion pair recognition

On 7/29/2026 1:17 AM, Jin Ma wrote:
> Add recognition for the following macro-fusion pairs:
>
>    RISCV_FUSE_SUB_SEQZ        - sub/subw + seqz/snez
>    RISCV_FUSE_ADD_LD          - add type + integer load
>    RISCV_FUSE_ADD_ST          - add type + integer store
>    RISCV_FUSE_ADD_ANDI        - add/addi type + andi type
>    RISCV_FUSE_ANDI_ADD        - andi type + add/addi type
>    RISCV_FUSE_LOGIC_LOGIC     - logic + logic
>    RISCV_FUSE_SLLI_SRLI       - slli/slliw + srli/srliw
>    RISCV_FUSE_SRLI_ADD        - srli/srliw + add type
>    RISCV_FUSE_PREINDEX_LD     - addi type + load
>    RISCV_FUSE_PREINDEX_ST     - addi type + store
>    RISCV_FUSE_POSTINDEX_LD    - load + addi type
>    RISCV_FUSE_POSTINDEX_ST    - store + addi type
>    RISCV_FUSE_LDST_PAIR_INC   - ascending integer load/store pair
>    RISCV_FUSE_LDST_PAIR_DEC   - descending integer load/store pair
>    RISCV_FUSE_FLDFST_PAIR_INC - ascending FP load/store pair
>    RISCV_FUSE_FLDFST_PAIR_DEC - descending FP load/store pair
>
> Leave the pairs disabled by default and mark positive checks as XFAIL.
>
> gcc/ChangeLog:
>
> 	* config/riscv/riscv-fusion.cc: Include insn-attr.h.
> 	(riscv_fusion_same_source_p, riscv_set_is_addw_p,
> 	riscv_set_is_word_add_p, riscv_set_is_addiw_p, riscv_insn_is_mv_li_p,
> 	riscv_insn_is_addi_type_p, riscv_insn_is_nonword_addi_type_p,
> 	riscv_insn_is_add_type_p, riscv_insn_is_add_addi_p,
> 	riscv_insn_is_sub_type_p, riscv_insn_is_andi_type_p,
> 	riscv_insn_is_logical_type_p, riscv_set_is_slli_p,
> 	riscv_set_is_slliw_p, riscv_set_is_srli_p, riscv_set_is_srliw_p,
> 	riscv_set_is_word_shift_p, riscv_fusion_extract_address,
> 	riscv_fusion_load_store, riscv_insn_is_load_store_type_p): New
> 	helper functions.
> 	(riscv_fuse_sub_seqz, riscv_fuse_add_andi, riscv_fuse_add_ldst_1,
> 	riscv_fuse_add_ld, riscv_fuse_add_st, riscv_fuse_andi_add,
> 	riscv_fuse_logic_logic, riscv_fuse_slli_srli, riscv_fuse_srli_add,
> 	riscv_fuse_preindex_ldst_1, riscv_fuse_preindex_ld,
> 	riscv_fuse_preindex_st, riscv_fuse_postindex_ldst_1,
> 	riscv_fuse_postindex_ld, riscv_fuse_postindex_st,
> 	riscv_fuse_ldst_pair_1, riscv_fuse_ldst_pair_inc,
> 	riscv_fuse_ldst_pair_dec, riscv_fuse_fldfst_pair_inc,
> 	riscv_fuse_fldfst_pair_dec): New function implementing the
> 	corresponding RISCV_FUSE_* pair.
> 	(riscv_fusion_table): Add entries for the new pairs.
> 	* config/riscv/riscv-protos.h (enum riscv_fusion_pairs): Add pair
> 	flags.
This is getting pretty large and tedious to try and work through from a 
review standpoint.  I hate to ask, but can we break this down into 
individual cases to aid review?

jeff