Re: [PATCH 2/3] RISC-V: optimize stack manipulation in save-restore

[Jeff Law via Gcc-patches]

On 12/1/22 03:03, Fei Gao wrote:
The stack that save-restore reserves is not well accumulated in stack 
allocation and deallocation.
This patch allows less instructions to be used in stack allocation and 
deallocation if save-restore enabled.

before patch:
   bar:
     call       t0,__riscv_save_4
     addi       sp,sp,-64
     ...
     li t0,-12288
     addi       t0,t0,-1968 # optimized out after patch
     add        sp,sp,t0 # prologue
     ...
     li t0,12288 # epilogue
     addi       t0,t0,2000 # optimized out after patch
     add        sp,sp,t0
     ...
     addi       sp,sp,32
     tail       __riscv_restore_4

after patch:
   bar:
     call       t0,__riscv_save_4
     addi       sp,sp,-2032
     ...
     li t0,-12288
     add        sp,sp,t0 # prologue
     ...
     li t0,12288 # epilogue
     add        sp,sp,t0
     ...
     addi       sp,sp,2032
     tail       __riscv_restore_4

gcc/ChangeLog:

         * config/riscv/riscv.cc (riscv_expand_prologue): consider save-restore 
in stack allocation.
         (riscv_expand_epilogue): consider save-restore in stack deallocation.

gcc/testsuite/ChangeLog:

         * gcc.target/riscv/stack_save_restore.c: New test.
I made a couple of whitespace fixes and pushed this to the trunk after 
running it through a cross testing cycle.

Thanks!

jeff