[clang] [CIR] Implement cir.cmp3way Operation (PR #186294)

[via cfe-commits]

github-actions[bot] wrote:

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

* 88065 tests passed
* 762 tests skipped
* 2 tests failed

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

### Clang
<details>
<summary>Clang.CIR/CodeGenCXX/three-way-comparison.cpp</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/clang -cc1 -internal-isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/lib/clang/23/include -nostdsysteminc -std=c++20 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/CIR/CodeGenCXX/three-way-comparison.cpp -o /home/gha/actions-runner/_work/llvm-project/llvm-project/build/tools/clang/test/CIR/CodeGenCXX/Output/three-way-comparison.cpp.tmp.cir
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/clang -cc1 -internal-isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/lib/clang/23/include -nostdsysteminc -std=c++20 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/CIR/CodeGenCXX/three-way-comparison.cpp -o /home/gha/actions-runner/_work/llvm-project/llvm-project/build/tools/clang/test/CIR/CodeGenCXX/Output/three-way-comparison.cpp.tmp.cir
# .---command stderr------------
# | /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/CIR/CodeGenCXX/three-way-comparison.cpp:4:10: fatal error: 'Inputs/std-compare.h' file not found
# |     4 | #include "Inputs/std-compare.h"
# |       |          ^~~~~~~~~~~~~~~~~~~~~~
# | 1 error generated.
# `-----------------------------
# error: command failed with exit status: 1

--

```
</details>
<details>
<summary>Clang.CIR/CodeGenCXX/three-way-comparison.cpp</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/clang -cc1 -internal-isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/lib/clang/23/include -nostdsysteminc -std=c++20 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/CIR/CodeGenCXX/three-way-comparison.cpp -o /home/gha/actions-runner/_work/llvm-project/llvm-project/build/tools/clang/test/CIR/CodeGenCXX/Output/three-way-comparison.cpp.tmp.cir
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/clang -cc1 -internal-isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/lib/clang/23/include -nostdsysteminc -std=c++20 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/CIR/CodeGenCXX/three-way-comparison.cpp -o /home/gha/actions-runner/_work/llvm-project/llvm-project/build/tools/clang/test/CIR/CodeGenCXX/Output/three-way-comparison.cpp.tmp.cir
# .---command stderr------------
# | /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/CIR/CodeGenCXX/three-way-comparison.cpp:4:10: fatal error: 'Inputs/std-compare.h' file not found
# |     4 | #include "Inputs/std-compare.h"
# |       |          ^~~~~~~~~~~~~~~~~~~~~~
# | 1 error generated.
# `-----------------------------
# 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/186294