[llvm] [LoongArch] Pre-commit test for vector trunc (PR #131082)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve-vla` running on `linaro-g3-01` while building `llvm` at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/17/builds/6469

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

```
Step 7 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'LLVM :: CodeGen/LoongArch/lsx/vec-trunc.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 2: /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/llc --mtriple=loongarch64 --mattr=+lsx /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll -o - | /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll
+ /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll
+ /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/stage1/bin/llc --mtriple=loongarch64 --mattr=+lsx /home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll -o -
/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll:7:15: error: CHECK-NEXT: is not on the line after the previous match
; CHECK-NEXT: vld $vr0, $a0, 0
              ^
<stdin>:9:2: note: 'next' match was here
 vld $vr0, $a0, 0
 ^
<stdin>:7:9: note: previous match ended here
# %bb.0:
        ^
<stdin>:8:1: note: non-matching line after previous match is here
 addi.d $sp, $sp, -16
^
/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll:22:15: error: CHECK-NEXT: is not on the line after the previous match
; CHECK-NEXT: vld $vr0, $a0, 0
              ^
<stdin>:27:2: note: 'next' match was here
 vld $vr0, $a0, 0
 ^
<stdin>:25:9: note: previous match ended here
# %bb.0:
        ^
<stdin>:26:1: note: non-matching line after previous match is here
 addi.d $sp, $sp, -16
^
/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll:37:15: error: CHECK-NEXT: is not on the line after the previous match
; CHECK-NEXT: vld $vr0, $a0, 0
              ^
<stdin>:46:2: note: 'next' match was here
 vld $vr0, $a0, 0
 ^
<stdin>:44:9: note: previous match ended here
# %bb.0:
        ^
<stdin>:45:1: note: non-matching line after previous match is here
 addi.d $sp, $sp, -16
^
/home/tcwg-buildbot/worker/clang-aarch64-sve-vla/llvm/llvm/test/CodeGen/LoongArch/lsx/vec-trunc.ll:52:15: error: CHECK-NEXT: is not on the line after the previous match
; CHECK-NEXT: vld $vr0, $a0, 0
              ^
<stdin>:65:2: note: 'next' match was here
 vld $vr0, $a0, 0
 ^
...

```

</details>

https://github.com/llvm/llvm-project/pull/131082