[llvm] AMDGPU: Expand shuffle testing with generated tests (PR #123574)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `premerge-monolithic-windows` running on `premerge-windows-1` while building `llvm` at step 8 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/35/builds/6444

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 8 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/AMDGPU/shufflevector.v2p0.v2p0.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
c:\ws\buildbot\premerge-monolithic-windows\build\bin\llc.exe -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 < C:\ws\buildbot\premerge-monolithic-windows\llvm-project\llvm\test\CodeGen\AMDGPU\shufflevector.v2p0.v2p0.ll | c:\ws\buildbot\premerge-monolithic-windows\build\bin\filecheck.exe -check-prefixes=GFX9,GFX900 C:\ws\buildbot\premerge-monolithic-windows\llvm-project\llvm\test\CodeGen\AMDGPU\shufflevector.v2p0.v2p0.ll
# executed command: 'c:\ws\buildbot\premerge-monolithic-windows\build\bin\llc.exe' -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900
# .---command stderr------------
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# | error: couldn't allocate input reg for constraint '{s[10:13]}'
# `-----------------------------
# error: command failed with exit status: 1
# executed command: 'c:\ws\buildbot\premerge-monolithic-windows\build\bin\filecheck.exe' -check-prefixes=GFX9,GFX900 'C:\ws\buildbot\premerge-monolithic-windows\llvm-project\llvm\test\CodeGen\AMDGPU\shufflevector.v2p0.v2p0.ll'
# .---command stderr------------
# | C:\ws\buildbot\premerge-monolithic-windows\llvm-project\llvm\test\CodeGen\AMDGPU\shufflevector.v2p0.v2p0.ll:1015:16: error: GFX900-NEXT: expected string not found in input
# | ; GFX900-NEXT: ;;#ASMSTART
# |                ^
# | <stdin>:852:41: note: scanning from here
# |  s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
# |                                         ^
# | <stdin>:856:2: note: possible intended match here
# |  ; -- End function
# |  ^
# | C:\ws\buildbot\premerge-monolithic-windows\llvm-project\llvm\test\CodeGen\AMDGPU\shufflevector.v2p0.v2p0.ll:1045:16: error: GFX900-NEXT: expected string not found in input
# | ; GFX900-NEXT: ;;#ASMSTART
# |                ^
...

```

</details>

https://github.com/llvm/llvm-project/pull/123574