[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-linux` running on `premerge-linux-1` while building `llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/20317

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

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/AMDGPU/shufflevector.v2f16.v2f16.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 2: /build/buildbot/premerge-monolithic-linux/build/bin/llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 < /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/CodeGen/AMDGPU/shufflevector.v2f16.v2f16.ll | /build/buildbot/premerge-monolithic-linux/build/bin/FileCheck -check-prefixes=GFX9,GFX900 /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/CodeGen/AMDGPU/shufflevector.v2f16.v2f16.ll
+ /build/buildbot/premerge-monolithic-linux/build/bin/llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900
+ /build/buildbot/premerge-monolithic-linux/build/bin/FileCheck -check-prefixes=GFX9,GFX900 /build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/CodeGen/AMDGPU/shufflevector.v2f16.v2f16.ll
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
error: couldn't allocate input reg for constraint '{s[10:10]}'
/build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/CodeGen/AMDGPU/shufflevector.v2f16.v2f16.ll:983:16: error: GFX900-NEXT: expected string not found in input
; GFX900-NEXT: ;;#ASMSTART
               ^
<stdin>:842:41: note: scanning from here
 s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
                                        ^
<stdin>:846:2: note: possible intended match here
 ; -- End function
 ^
/build/buildbot/premerge-monolithic-linux/llvm-project/llvm/test/CodeGen/AMDGPU/shufflevector.v2f16.v2f16.ll:1013:16: error: GFX900-NEXT: expected string not found in input
; GFX900-NEXT: ;;#ASMSTART
               ^
<stdin>:869:41: note: scanning from here
 s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
                                        ^
<stdin>:873:2: note: possible intended match here
 ; -- End function
...

```

</details>

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