[Bug ld/31175] New: RISCV load immediate relaxation leaves redundant addi

[iwfinlay at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31175

            Bug ID: 31175
           Summary: RISCV load immediate relaxation leaves redundant addi
           Product: binutils
           Version: 2.39
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: iwfinlay at gmail dot com
  Target Milestone: ---

Created attachment 15261
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15261&action=edit
Tar of --save-temps and source to build image

Per the GCC g++ feedback (originally filed there), linker relaxation should
remove the addi/mv in the cases 1, 2, 3. The following is an excerpt from
objdump of the ELF.

20010064 <_Z6globalv>:
20010064:       80000537                lui     a0,0x80000
20010068:       00050513                mv      a0,a0           <-- (1)
2001006c:       00008067                ret

20010070 <_Z4initv>:
20010070:       800007b7                lui     a5,0x80000
20010074:       00078793                mv      a5,a5           <-- (2)
20010078:       3e700713                li      a4,999
2001007c:       00e7a223                sw      a4,4(a5) # 80000004
<__global_pointer$+0xfffff804>
20010080:       0ea00713                li      a4,234
20010084:       00e7a423                sw      a4,8(a5)
20010088:       00008067                ret

2001008c <_Z5pcnt0v>:
2001008c:       800007b7                lui     a5,0x80000
20010090:       00078793                mv      a5,a5           <-- (3)
20010094:       0047a703                lw      a4,4(a5) # 80000004
<__global_pointer$+0xfffff804>
20010098:       60271713                cpop    a4,a4

Command line:
riscv64-unknown-elf-g++ --save-temps -march=rv32imv_zbb_zbs -mabi=ilp32 -O3
-Wall -Wextra -o relax.elf main.cpp test.cpp startup.cpp -fno-builtin -static
-fno-common -mcmodel=medlow -nostdlib -T link.ld
riscv64-unknown-elf-objdump -d relax.elf > relax.disasm

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