[Bug target/109279] [13 Regression] RISC-V: complex constants synthesized vs. fetching from constant pool

[vineet.gupta at linux dot dev via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109279

--- Comment #3 from Vineet Gupta <vineet.gupta at linux dot dev> ---
We start off with following:

  (insn 18 17 19 2 (set (reg:DI 154)
     (mem/u/c:DI (reg/f:DI 155) [0  S8 A64])) "...":9:8 179 {*movdi_64bit}
     (expr_list:REG_DEAD (reg/f:DI 155)
        (expr_list:REG_EQUAL (const_int [0x101010101010101])

cse1 matches the new pattern and converts mem to const_int.

   (insn 18 17 19 2 (set (reg:DI 154)
        (const_int [0x101010101010101])) "...":9:8 177 {*mvconst_internal}
     (expr_list:REG_DEAD (reg/f:DI 155)
        (expr_list:REG_EQUAL (const_int [0x101010101010101])

split1 then does its job, again using the introduced define_insn_and_split
"*mvconst_internal"

Splitting with gen_split_15 (riscv.md:1677)
deleting insn with uid = 18.

   (insn 47 15 48 2 (set (reg:DI 154)
        (const_int 16842752 [0x1010000])) "...":9:8 -1

   (insn 48 47 49 2 (set (reg:DI 154)
        (plus:DI (reg:DI 154)
            (const_int 257 [0x101]))) "...":9:8 -1

   (insn 49 48 50 2 (set (reg:DI 154)
        (ashift:DI (reg:DI 154)
            (const_int 16 [0x10]))) "...":9:8 -1

   (insn 50 49 51 2 (set (reg:DI 154)
        (plus:DI (reg:DI 154)
            (const_int 257 [0x101]))) "...":9:8 -1

   (insn 51 50 52 2 (set (reg:DI 154)
        (ashift:DI (reg:DI 154)
            (const_int 16 [0x10]))) "...":9:8 -1

   (insn 52 51 19 2 (set (reg:DI 154)
        (plus:DI (reg:DI 154)
            (const_int 257 [0x101]))) "...":9:8 -1
     (expr_list:REG_EQUAL (const_int [0x101010101010101])