[Bug target/106602] riscv: suboptimal codegen for zero_extendsidi2_shifted w/o bitmanip

[vineetg at rivosinc dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106602

--- Comment #22 from Vineet Gupta <vineetg at rivosinc dot com> ---
(In reply to Vineet Gupta from comment #21)


> However 
>  try_combine
>     recog_for_combine
>       recog_for_combine_1
>          recog( )
> 
> is failing and we get "Failed to recognize..."

False alarm: In a different successful split case, recog() does fail initially
too. I see split_insns correctly returning the first shift-right.

  (insn 22 0 23 (set (reg:DI 77)
        (lshiftrt:DI (reg:DI 76)
            (const_int 6 [0x6]))) -1
     (nil))

debugging....