[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 `clang-aarch64-quick` running on `linaro-clang-aarch64-quick` while building `llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/65/builds/7978

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/20/include -nostdsysteminc -triple aarch64 -target-feature +sve -O1 -Werror -Wall -emit-llvm -o - /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -mvscale-min=1 -mvscale-max=1 | /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -D#VBITS=128 --check-prefixes=CHECK128
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -D#VBITS=128 --check-prefixes=CHECK128
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/20/include -nostdsysteminc -triple aarch64 -target-feature +sve -O1 -Werror -Wall -emit-llvm -o - /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -mvscale-min=1 -mvscale-max=1
RUN: at line 2: /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/20/include -nostdsysteminc -triple aarch64 -target-feature +sve -O1 -Werror -Wall -emit-llvm -o - /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -mvscale-min=2 -mvscale-max=2 | /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -D#VBITS=256 --check-prefixes=CHECK,CHECK256
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/20/include -nostdsysteminc -triple aarch64 -target-feature +sve -O1 -Werror -Wall -emit-llvm -o - /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -mvscale-min=2 -mvscale-max=2
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c -D#VBITS=256 --check-prefixes=CHECK,CHECK256
/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c:62:16: error: CHECK-SAME: expected string not found in input
// CHECK-SAME: ptr dead_on_unwind noalias nocapture writable writeonly sret(<[[#div(VBITS,8)]] x i8>) align 16 %agg.result, ptr nocapture noundef readonly %0)
               ^
<stdin>:9:27: note: scanning from here
define dso_local void @f2(ptr dead_on_unwind noalias nocapture writable writeonly sret(<32 x i8>) align 16 initializes((0, 32)) %agg.result, ptr nocapture noundef readonly %0) local_unnamed_addr #0 {
                          ^
<stdin>:9:27: note: with "div(VBITS,8)" equal to "32"
define dso_local void @f2(ptr dead_on_unwind noalias nocapture writable writeonly sret(<32 x i8>) align 16 initializes((0, 32)) %agg.result, ptr nocapture noundef readonly %0) local_unnamed_addr #0 {
                          ^
/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c:92:93: error: undefined variable: TBAA6
// CHECK-NEXT: store <[[#div(VBITS,8)]] x i8> [[X]], ptr [[INDIRECT_ARG_TEMP]], align 16, [[TBAA6]]
                                                                                            ^
<stdin>:37:71: note: with "div(VBITS,8)" equal to "32"
 call void @llvm.lifetime.start.p0(i64 32, ptr nonnull %byval-temp) #6
                                                                      ^
<stdin>:37:71: note: with "X" equal to "%x"
 call void @llvm.lifetime.start.p0(i64 32, ptr nonnull %byval-temp) #6
                                                                      ^
<stdin>:37:71: note: with "INDIRECT_ARG_TEMP" equal to "%byval-temp"
 call void @llvm.lifetime.start.p0(i64 32, ptr nonnull %byval-temp) #6
                                                                      ^
<stdin>:38:2: note: possible intended match here
 store <32 x i8> %x, ptr %byval-temp, align 16, !tbaa !2
 ^

Input file: <stdin>
Check file: /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c

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

Input was:
<<<<<<
           1: ; ModuleID = '/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c' 
           2: source_filename = "/home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGen/AArch64/sve-acle-__ARM_FEATURE_SVE_VECTOR_OPERATORS.c" 
           3: target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32" 
           4: target triple = "aarch64" 
           5:  
           6: @x256 = local_unnamed_addr global <4 x i64> <i64 0, i64 1, i64 2, i64 3>, align 16 
           7:  
...

```

</details>

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