Re: [PATCH] RISC-V: improve codegen for large constants with same 32-bit lo and hi parts [2]

[Palmer Dabbelt]

On Fri, 19 May 2023 09:33:34 PDT (-0700), jeffreya...@gmail.com wrote:


On 5/18/23 14:57, Vineet Gupta wrote:
[part #2 of PR/109279]

SPEC2017 deepsjeng uses large constants which currently generates less than
ideal code. This fix improves codegen for large constants which have
same low and hi parts: e.g.

        long long f(void) { return 0x0101010101010101ull; }

Before
         li      a5,0x1010000
         addi    a5,a5,0x101
         mv      a0,a5
         slli    a5,a5,32
         add     a0,a5,a0
         ret

With patch
        li      a5,0x1010000
        addi    a5,a5,0x101
        slli    a0,a5,32
        add     a0,a0,a5
        ret

This is testsuite clean.

gcc/ChangeLog:

        * config/riscv/riscv.cc (riscv_split_integer): if loval is equal
          to hival, ASHIFT the corresponding regs.
LGTM.  Please install.  Thanks for taking care of this!  The updated
sequence looks good.

Works for me.  Did you start that performance backports branch?  Either 
way, I think this should go on it.