[llvm] [IR][RFC] Add @llvm.mask.beforefirst intrinsic (PR #203874)

[via llvm-commits]

github-actions[bot] wrote:

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

* 138677 tests passed
* 3564 tests skipped
* 1 test failed

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

### LLVM
<details>
<summary>LLVM.CodeGen/AArch64/mask-beforefirst-sve.ll</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
c:\_work\llvm-project\llvm-project\build\bin\llc.exe < C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\AArch64\mask-beforefirst-sve.ll -mtriple aarch64 -mattr=+sve | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\AArch64\mask-beforefirst-sve.ll
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\llc.exe' -mtriple aarch64 -mattr=+sve
# note: command had no output on stdout or stderr
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' 'C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\AArch64\mask-beforefirst-sve.ll'
# .---command stderr------------
# | C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\AArch64\mask-beforefirst-sve.ll:144:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: cset w8, ne
# |               ^
# | <stdin>:174:16: note: scanning from here
# |  ptest p0, p0.b
# |                ^
# | <stdin>:175:2: note: possible intended match here
# |  csetm x8, ne
# |  ^
# | 
# | Input file: <stdin>
# | Check file: C:\_work\llvm-project\llvm-project\llvm\test\CodeGen\AArch64\mask-beforefirst-sve.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |             .
# |             .
# |             .
# |           169:  .cfi_startproc 
# |           170: // %bb.0: 
# |           171:  ptrue p2.b 
# |           172:  brkb p0.b, p2/z, p0.b 
# |           173:  brkb p1.b, p2/z, p1.b 
# |           174:  ptest p0, p0.b 
# | next:144'0                   {   search range start (exclusive)
# | next:144'1                       error: no match found in search range
# |           175:  csetm x8, ne 
# | next:144'2      ?              possible intended match
# |           176:  whilelo p3.b, xzr, x8 
# |           177:  bic p1.b, p1/z, p1.b, p3.b 
# |           178:  ret 
# |           179: .Lfunc_end9: 
# |           180:  .size nxv32i1, .Lfunc_end9-nxv32i1 
# |           181:  .cfi_endproc 
# |           182:  // -- End function 
# |           183:  .section ".note.GNU-stack","", at progbits 
# | next:144'3                                              } search range end (exclusive)
# | >>>>>>
# `-----------------------------
# 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/203874