[llvm] [PGO] Fix zeroed estimated trip count (PR #167792)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/31638

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 5
/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/opt -passes=loop-vectorize -S /Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll | /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll
# executed command: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/opt -passes=loop-vectorize -S /Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll
# .---command stderr------------
# | /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/opt: warning: failed to infer data layout: unable to get target for 'x86_64-unknown-linux-gnu', see --version and --triple.
# | /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/opt: WARNING: failed to create target machine for 'x86_64-unknown-linux-gnu': unable to get target for 'x86_64-unknown-linux-gnu', see --version and --triple.
# `-----------------------------
# executed command: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll
# .---command stderr------------
# | /Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll:11:10: error: CHECK: expected string not found in input
# | ; CHECK: vector.memcheck:
# |          ^
# | <stdin>:5:19: note: scanning from here
# | define void @test(ptr addrspace(1) %p, i32 %n) {
# |                   ^
# | <stdin>:9:18: note: possible intended match here
# | outer: ; preds = %outer.latch, %entry
# |                  ^
# | 
# | Input file: <stdin>
# | Check file: /Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |             1: ; ModuleID = '/Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll' 
# |             2: source_filename = "/Users/buildbot/buildbot-root/llvm-project/llvm/test/Transforms/LoopVectorize/vectorize-zero-estimated-trip-count.ll" 
# |             3: target triple = "x86_64-unknown-linux-gnu" 
# |             4:  
# |             5: define void  at test(ptr addrspace(1) %p, i32 %n) { 
# | check:10                   ^~~~~~
# | check:11'0                       X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
# |             6: entry: 
# | check:11'0     ~~~~~~~
# |             7:  br label %outer 
# | check:11'0     ~~~~~~~~~~~~~~~~~
# |             8:  
# | check:11'0     ~
# |             9: outer: ; preds = %outer.latch, %entry 
# | check:11'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | check:11'1                      ?                     possible intended match
# |            10:  br label %inner 
# | check:11'0     ~~~~~~~~~~~~~~~~~
# |            11:  
...

```

</details>

https://github.com/llvm/llvm-project/pull/167792