[llvm] [FunctionAttrs] Add the "initializes" attribute inference (PR #97373)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-win` running on `sie-win-worker` while building `llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/46/builds/8113

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: CodeGen/SystemZ/systemz-inline-asm.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
z:\b\llvm-clang-x86_64-sie-win\build\bin\clang.exe -cc1 -internal-isystem Z:\b\llvm-clang-x86_64-sie-win\build\lib\clang\20\include -nostdsysteminc -triple s390x-linux-gnu -O2 -emit-llvm -o - Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\CodeGen\SystemZ\systemz-inline-asm.c | z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\CodeGen\SystemZ\systemz-inline-asm.c
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\clang.exe' -cc1 -internal-isystem 'Z:\b\llvm-clang-x86_64-sie-win\build\lib\clang\20\include' -nostdsysteminc -triple s390x-linux-gnu -O2 -emit-llvm -o - 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\CodeGen\SystemZ\systemz-inline-asm.c'
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe' 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\CodeGen\SystemZ\systemz-inline-asm.c'
# .---command stderr------------
# | Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\CodeGen\SystemZ\systemz-inline-asm.c:126:11: error: CHECK: expected string not found in input
# | // CHECK: define{{.*}} void @test_f128(ptr dead_on_unwind noalias nocapture writable writeonly sret(fp128) align 8 [[DEST:%.*]], ptr nocapture noundef readonly %0, ptr nocapture noundef readonly %1)
# |           ^
# | <stdin>:124:73: note: scanning from here
# |  %0 = tail call double asm "adbr $0, $2", "=f,0,f"(double %f, double %g) #6, !srcloc !18
# |                                                                         ^
# | 
# | Input file: <stdin>
# | Check file: Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\CodeGen\SystemZ\systemz-inline-asm.c
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |              1: ; ModuleID = 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\CodeGen\SystemZ\systemz-inline-asm.c' 
# |              2: source_filename = "Z:\\b\\llvm-clang-x86_64-sie-win\\llvm-project\\clang\\test\\CodeGen\\SystemZ\\systemz-inline-asm.c" 
# |              3: target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64" 
# |              4: target triple = "s390x-unknown-linux-gnu" 
# |              5:  
# |              6:  at gi = global i32 0, align 4 
# |              7:  at gl = local_unnamed_addr global i64 0, align 8 
# |              8:  
# |              9: ; Function Attrs: nounwind 
# |             10: define dso_local void @test_store_m(i32 noundef zeroext %i) local_unnamed_addr #0 { 
# | label:8'0       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | label:8'1       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |             11: entry: 
# |             12:  tail call void asm "st $1, $0", "=*m,r"(ptr nonnull elementtype(i32) @gi, i32 %i) #4, !srcloc !2 
# | check:9               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |             13:  ret void 
# |             14: } 
# |             15:  
# |             16: ; Function Attrs: nounwind 
# |             17: define dso_local void @test_store_Q(i32 noundef zeroext %i) local_unnamed_addr #0 { 
# | label:14'0      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | label:14'1      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |             18: entry: 
# |             19:  tail call void asm "st $1, $0", "=*Q,r"(ptr nonnull elementtype(i32) @gi, i32 %i) #4, !srcloc !3 
# | check:15              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |             20:  ret void 
...

```

</details>

https://github.com/llvm/llvm-project/pull/97373