[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 `openmp-offload-sles-build-only` running on `rocm-worker-hw-04-sles` while building `llvm` at step 6 "Add check check-clang".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/11190

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

```
Step 6 (Add check check-clang) failure: test (failure)
******************** TEST 'Clang :: CodeGen/SystemZ/systemz-inline-asm.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/clang -cc1 -internal-isystem /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/lib/clang/20/include -nostdsysteminc -triple s390x-linux-gnu -O2 -emit-llvm -o - /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/clang/test/CodeGen/SystemZ/systemz-inline-asm.c | /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/FileCheck /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/clang/test/CodeGen/SystemZ/systemz-inline-asm.c
+ /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/FileCheck /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/clang/test/CodeGen/SystemZ/systemz-inline-asm.c
+ /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/bin/clang -cc1 -internal-isystem /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/lib/clang/20/include -nostdsysteminc -triple s390x-linux-gnu -O2 -emit-llvm -o - /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/clang/test/CodeGen/SystemZ/systemz-inline-asm.c
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/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: /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/clang/test/CodeGen/SystemZ/systemz-inline-asm.c

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

Input was:
<<<<<<
           .
           .
           .
         119: } 
         120:  
         121: ; Function Attrs: nofree nosync nounwind memory(none) 
         122: define dso_local double @test_f64(double noundef %f, double noundef %g) local_unnamed_addr #2 { 
         123: entry: 
         124:  %0 = tail call double asm "adbr $0, $2", "=f,0,f"(double %f, double %g) #6, !srcloc !18 
check:126                                                                             X~~~~~~~~~~~~~~~~ error: no match found
         125:  ret double %0 
check:126     ~~~~~~~~~~~~~~~
         126: } 
check:126     ~~
         127:  
check:126     ~
         128: ; Function Attrs: nounwind memory(argmem: readwrite) 
check:126     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         129: define dso_local void @test_f128(ptr dead_on_unwind noalias nocapture writable writeonly sret(fp128) align 8 initializes((0, 16)) %agg.result, ptr nocapture noundef readonly %0, ptr nocapture noundef readonly %1) local_unnamed_addr #3 { 
check:126     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           .
           .
           .
>>>>>>

--

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


```

</details>

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