[clang] [clang] Fix size and alignment of packed sub-byte integer vectors (PR #161796)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 51863 tests passed
* 908 tests skipped
* 1 test failed

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

### Clang
<details>
<summary>Clang.SemaCXX/constexpr-builtin-bit-cast.cpp</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -cc1 -internal-isystem C:\_work\llvm-project\llvm-project\build\lib\clang\23\include -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -cc1 -internal-isystem 'C:\_work\llvm-project\llvm-project\build\lib\clang\23\include' -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 'C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp'
# note: command had no output on stdout or stderr
# RUN: at line 2
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -cc1 -internal-isystem C:\_work\llvm-project\llvm-project\build\lib\clang\23\include -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp -fno-signed-char
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -cc1 -internal-isystem 'C:\_work\llvm-project\llvm-project\build\lib\clang\23\include' -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 'C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp' -fno-signed-char
# note: command had no output on stdout or stderr
# RUN: at line 3
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -cc1 -internal-isystem C:\_work\llvm-project\llvm-project\build\lib\clang\23\include -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple aarch64_be-linux-gnu C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -cc1 -internal-isystem 'C:\_work\llvm-project\llvm-project\build\lib\clang\23\include' -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple aarch64_be-linux-gnu 'C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp'
# note: command had no output on stdout or stderr
# RUN: at line 5
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -cc1 -internal-isystem C:\_work\llvm-project\llvm-project\build\lib\clang\23\include -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp -fexperimental-new-constant-interpreter
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -cc1 -internal-isystem 'C:\_work\llvm-project\llvm-project\build\lib\clang\23\include' -nostdsysteminc -verify -std=c++2a -fsyntax-only -triple x86_64-apple-macosx10.14.0 'C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp' -fexperimental-new-constant-interpreter
# .---command stderr------------
# | error: 'expected-error' diagnostics expected but not seen: 
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 152 (directive at C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp:150): constexpr variable 'g' must be initialized by a constant expression
# | error: 'expected-error' diagnostics seen but not expected: 
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 526: static assertion failed due to requirement 'bit_cast<unsigned char>(_BitInt(2) __attribute__((ext_vector_type(4))){1, -2, 0, -1}) == (1 ? 201 : 99)': 
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 527: static assertion failed due to requirement 'bit_cast<unsigned short>(_BitInt(2) __attribute__((ext_vector_type(8))){1, -2, 0, -1, -2, -1, 1, 0}) == (1 ? 7881 : 25524)': 
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 536: static assertion failed due to requirement 'bit_cast<unsigned char>(_BitInt(4) __attribute__((ext_vector_type(2))){-4, -7}) == (1 ? 156 : 201)': 
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 537: static assertion failed due to requirement 'bit_cast<unsigned short>(_BitInt(4) __attribute__((ext_vector_type(4))){3, -5, -1, 7}) == (1 ? 32691 : 15351)': 
# | error: 'expected-note' diagnostics expected but not seen: 
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 152 (directive at C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp:151): constexpr bit_cast involving bit-field is not yet supported
# | error: 'expected-note' diagnostics seen but not expected: 
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 526: expression evaluates to '0 == 201'
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 527: expression evaluates to '0 == 7881'
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 536: expression evaluates to '0 == 156'
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 537: expression evaluates to '0 == 32691'
# |   File C:\_work\llvm-project\llvm-project\clang\test\SemaCXX\constexpr-builtin-bit-cast.cpp Line 596: indeterminate value can only initialize an object of type 'unsigned char' or 'std::byte'; 'char' is invalid
# | 11 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/161796