[clang] [llvm] [X86][MC,Driver] Support -msse2avx to encode SSE instruction with VEX prefix (PR #96860)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-quick` running on `linaro-clang-aarch64-quick` while building `clang,llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/65/builds/1438

Here is the relevant piece of the build log for the reference:
```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: Driver/msse2avx.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -### -c -march=x86-64 -Xassembler -msse2avx /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/Driver/msse2avx.c 2>&1 | /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck  /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/Driver/msse2avx.c
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -### -c -march=x86-64 -Xassembler -msse2avx /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/Driver/msse2avx.c
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/Driver/msse2avx.c
/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/Driver/msse2avx.c:4:11: error: CHECK: expected string not found in input
// CHECK: "-msse2avx"
          ^
<stdin>:1:1: note: scanning from here
clang version 19.0.0git (https://github.com/llvm/llvm-project.git bddab518db003f7c5ce9014e9ebd932fb7a85d2f)
^
<stdin>:6:36: note: possible intended match here
clang: error: unsupported argument '-msse2avx' to option '-Xassembler'
                                   ^

Input file: <stdin>
Check file: /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/Driver/msse2avx.c

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           1: clang version 19.0.0git (https://github.com/llvm/llvm-project.git bddab518db003f7c5ce9014e9ebd932fb7a85d2f) 
check:4'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
           2: Target: aarch64-unknown-linux-gnu 
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           3: Thread model: posix 
check:4'0     ~~~~~~~~~~~~~~~~~~~~
           4: InstalledDir: /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin 
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           5: Build config: +assertions 
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~
           6: clang: error: unsupported argument '-msse2avx' to option '-Xassembler' 
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
check:4'1                                        ?                                    possible intended match
           7: clang: error: unsupported argument 'x86-64' to option '-march=' 
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           8:  (in-process) 
check:4'0     ~~~~~~~~~~~~~~
           9:  "/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang-19" "-cc1" "-triple" "aarch64-unknown-linux-gnu" "-emit-obj" "-disable-free" "-clear-ast-before-backend" "-main-file-name" "msse2avx.c" "-mrelocation-model" "pic" "-pic-level" "2" "-pic-is-pie" "-mframe-pointer=non-leaf" "-fmath-errno" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-funwind-tables=2" "-target-cpu" "generic" "-target-abi" "aapcs" "-debugger-tuning=gdb" "-fdebug-compilation-dir=/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/test/Driver" "-fcoverage-compilation-dir=/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/tools/clang/test/Driver" "-resource-dir" "/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/19" "-internal-isystem" "/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/19/include" "-internal-isystem" "/usr/local/include" "-internal-isystem" "/usr/lib/gcc/aarch64-linux-gnu/10/../../../../aarch64-linux-gnu/include" "-internal-externc-isystem" "/usr/include/aarch64-linux-gnu" "-internal-externc-isystem" "/include" "-internal-externc-isystem" "/usr/include" "-ferror-limit" "19" "-fno-signed-char" "-fgnuc-version=4.2.1" "-fskip-odr-check-in-gmf" "-target-feature" "+outline-atomics" "-target-feature" "-fmv" "-faddrsig" "-D__GCC_HAVE_DWARF2_CFI_ASM=1" "-o" "msse2avx.o" "-x" "c" "/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/Driver/msse2avx.c" 
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>>

--

********************


```

https://github.com/llvm/llvm-project/pull/96860