[llvm] [llvm-objdump] Fix output corruption when DWARF reg-name callback misses. (PR #200975)

[via llvm-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Linux-->
# :penguin: Linux x64 Test Results

* 179536 tests passed
* 3573 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### LLVM
<details>
<summary>LLVM.CodeGen/AMDGPU/packed-fp64.ll</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llc -global-isel=0 -mtriple=amdgpu12.51 < /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/CodeGen/AMDGPU/packed-fp64.ll | /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/FileCheck -enable-var-scope -check-prefixes=GFX1251,GFX1251-SDAG /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/CodeGen/AMDGPU/packed-fp64.ll
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llc -global-isel=0 -mtriple=amdgpu12.51
# note: command had no output on stdout or stderr
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/FileCheck -enable-var-scope -check-prefixes=GFX1251,GFX1251-SDAG /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/CodeGen/AMDGPU/packed-fp64.ll
# .---command stderr------------
# | /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/CodeGen/AMDGPU/packed-fp64.ll:2672:22: error: GFX1251-SDAG-NEXT: expected string not found in input
# | ; GFX1251-SDAG-NEXT: global_wb
# |                      ^
# | <stdin>:3515:9: note: scanning from here
# | ; %bb.0:
# |         ^
# | <stdin>:3516:2: note: possible intended match here
# |  global_prefetch_b8 v0, s[0:1] scope:SCOPE_SE
# |  ^
# | /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/CodeGen/AMDGPU/packed-fp64.ll:2734:22: error: GFX1251-SDAG-NEXT: expected string not found in input
# | ; GFX1251-SDAG-NEXT: global_wb
# |                      ^
# | <stdin>:3585:9: note: scanning from here
# | ; %bb.0:
# |         ^
# | <stdin>:3586:2: note: possible intended match here
# |  global_prefetch_b8 v0, s[0:1] scope:SCOPE_SE
# |  ^
# | 
# | Input file: <stdin>
# | Check file: /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/CodeGen/AMDGPU/packed-fp64.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |              .
# |              .
# |              .
# |           3510:  .text 
# |           3511:  .globl fma_v2_s_imm_imm ; -- Begin function fma_v2_s_imm_imm 
# |           3512:  .p2align 8 
# |           3513:  .type fma_v2_s_imm_imm, at function 
# |           3514: fma_v2_s_imm_imm: ; @fma_v2_s_imm_imm 
# |           3515: ; %bb.0: 
# | next:2672'0            {   search range start (exclusive)
# | next:2672'1                error: no match found in search range
# |           3516:  global_prefetch_b8 v0, s[0:1] scope:SCOPE_SE 
# | next:2672'2      ?                                              possible intended match
# |           3517:  v_nop 
# |           3518:  s_setreg_imm32_b32 hwreg(HW_REG_WAVE_MODE, 25, 1), 1 ; msbs: dst=0 src0=0 src1=0 src2=0 
# |           3519:  s_load_b64 s[2:3], s[4:5], 0x24 nv 
# |           3520:  s_wait_xcnt 0x0 
# |           3521:  s_mov_b64 s[4:5], 0x4069000000000000 
# |              .
# |              .
# |              .
# |           3579:  .long 0 
# |           3580:  .text 
# |           3581:  .globl fma_v2_imm_imm_s ; -- Begin function fma_v2_imm_imm_s 
# |           3582:  .p2align 8 
# |           3583:  .type fma_v2_imm_imm_s, at function 
# |           3584: fma_v2_imm_imm_s: ; @fma_v2_imm_imm_s 
# | next:2672'3                      }                      search range end (exclusive)
# |           3585: ; %bb.0: 
# | next:2734'0            {   search range start (exclusive)
# | next:2734'1                error: no match found in search range
# |           3586:  global_prefetch_b8 v0, s[0:1] scope:SCOPE_SE 
# | next:2734'2      ?                                              possible intended match
# |           3587:  v_nop 
# |           3588:  s_setreg_imm32_b32 hwreg(HW_REG_WAVE_MODE, 25, 1), 1 ; msbs: dst=0 src0=0 src1=0 src2=0 
# |           3589:  s_load_b64 s[2:3], s[4:5], 0x24 nv 
# |           3590:  v_and_b32_e32 v0, 0x3ff, v0 
# |           3591:  s_wait_kmcnt 0x0 
# |              .
# |              .
# |              .
# |           3640:  .set amdgpu.max_num_agpr, 0 
# |           3641:  .set amdgpu.max_num_sgpr, 32 
# |           3642:  .set amdgpu.max_num_named_barrier, 0 
# |           3643:  .section .AMDGPU.csdata,"", at progbits 
# |           3644:  .section ".note.GNU-stack","", at progbits 
# |           3645:  .amd_amdgpu_isa "amdgpu12.51-unknown-unknown-unknown-gfx1251" 
# | next:2734'3                                                                    } search range end (exclusive)
# | >>>>>>
# `-----------------------------
# error: command failed with exit status: 1

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/200975