[clang] First draft: [Clang] Add constant evaluation support for x86 psadbw/p… (PR #169253)

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github-actions[bot] wrote:

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

* 84729 tests passed
* 1108 tests skipped
* 1 test failed

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

### Clang
<details>
<summary>Clang.AST/ByteCode/x86-psadbw-psadbw128.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/22/include -nostdsysteminc -std=c++20 -triple x86_64-unknown-linux-gnu -O0    -fexperimental-new-constant-interpreter -verify /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp
# 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/22/include -nostdsysteminc -std=c++20 -triple x86_64-unknown-linux-gnu -O0 -fexperimental-new-constant-interpreter -verify /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp
# .---command stderr------------
# | error: no expected directives found: consider use of 'expected-no-diagnostics'
# | error: 'expected-error' diagnostics seen but not expected: 
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp Line 20: static assertion expression is not an integral constant expression
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp Line 21: static assertion expression is not an integral constant expression
# | error: 'expected-note' diagnostics seen but not expected: 
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp Line 17: subexpression not valid in a constant expression
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp Line 20: in call to 'test_psadbw128()'
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp Line 17: subexpression not valid in a constant expression
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/AST/ByteCode/x86-psadbw-psadbw128.cpp Line 21: in call to 'test_psadbw128()'
# | 7 errors 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/169253