<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/108004>108004</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [LoopVectorize] Assertion fails when IV start value is used by an exit block PHI
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          hazzlim
      </td>
    </tr>
</table>

<pre>
    With the following IR:
```
define i64 @foo(i64 %start, i64 %end) {
entry:
  %p1 = alloca [1024 x i32]
 %p2 = alloca [1024 x i32]
  call void @init_mem(ptr %p1, i64 1024)
 call void @init_mem(ptr %p2, i64 1024)
  %start2 = and i64 %start, 12345
  br label %for.body

for.body:
  %ind = phi i64 [ %ind.next, %for.body ], [ %start2, %entry ]
  %arrayidx1 = getelementptr inbounds i32, ptr %p1, i64 %ind
  %0 = load i32, ptr %arrayidx1, align 4
  %arrayidx2 = getelementptr inbounds i32, ptr %p2, i64 %ind
  %1 = load i32, ptr %arrayidx2, align 4
  %ind.next = add i64 %ind, 1
  %cmp = icmp ne i64 %ind.next, %end
  br i1 %cmp, label %for.body, label %exit

exit:
  %use =  phi i64 [ %start2, %for.body ]
  ret i64 %use
}

declare void @init_mem(ptr, i64)
```

LV crashes due to hitting the following assertion:
```
LV: Vectorizing: innermost loop.
PHINode should have one entry for each predecessor of its parent basic block!
  %bob = phi i64 [ %start2, %for.body ]
opt: /work/llvm-project-wt/nuw-clang-arr/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:10244: bool llvm::LoopVectorizePass::processLoop(Loop *): Assertion `!verif
yFunction(*L->getHeader()->getParent(), &dbgs())' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: ./build/bin/opt -passes=loop-vectorize -force-vector-interleave=2 -force-vector-width=4 -debug test.ll -o - -S
1.      Running pass "function(loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>)" on module "test.ll"
2.      Running pass "loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>" on function "foo"
 #0 0x0000aaaaaec431c0 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (./build/bin/opt+0x41a31c0)
 #1 0x0000aaaaaec4102c llvm::sys::RunSignalHandlers() (./build/bin/opt+0x41a102c)
 #2 0x0000aaaaaec438dc SignalHandler(int) Signals.cpp:0:0
 #3 0x0000fffff7ffb9d0 (linux-vdso.so.1+0x9d0)
 #4 0x0000fffff7b5f200 __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #5 0x0000fffff7b1a67c gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #6 0x0000fffff7b07130 abort ./stdlib/abort.c:81:7
 #7 0x0000fffff7b13fd0 __assert_fail_base ./assert/assert.c:89:7
 #8 0x0000fffff7b14040 __assert_perror_fail ./assert/assert-perr.c:31:1
 #9 0x0000aaaaadee375c llvm::LoopVectorizePass::processLoop(llvm::Loop*) (./build/bin/opt+0x344375c)
#10 0x0000aaaaadee72d0 llvm::LoopVectorizePass::runImpl(llvm::Function&) (./build/bin/opt+0x34472d0)
#11 0x0000aaaaadee7ac0 llvm::LoopVectorizePass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (./build/bin/opt+0x3447ac0)
#12 0x0000aaaaaea9676c llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (./bui
ld/bin/opt+0x3ff676c)
#13 0x0000aaaaaea9a1fc llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (./build/bin/opt+0x3ffa1fc)
#14 0x0000aaaaaea958cc llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (./build/bin/o
pt+0x3ff58cc)
#15 0x0000aaaaab5b3d88 llvm::runPassPipeline(llvm::StringRef, llvm::Module&, llvm::TargetMachine*, llvm::TargetLibraryInfoImpl*, llvm::ToolOutputFile*, llvm::ToolOu
tputFile*, llvm::ToolOutputFile*, llvm::StringRef, llvm::ArrayRef<llvm::PassPlugin>, llvm::ArrayRef<std::function<void (llvm::PassBuilder&)>>, llvm::opt_tool::Outpu
tKind, llvm::opt_tool::VerifierKind, bool, bool, bool, bool, bool, bool, bool) (./build/bin/opt+0xb13d88)
#16 0x0000aaaaab5a7fc0 optMain (./build/bin/opt+0xb07fc0)
#17 0x0000fffff7b073fc __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#18 0x0000fffff7b074cc call_init ./csu/../csu/libc-start.c:128:20
#19 0x0000fffff7b074cc __libc_start_main ./csu/../csu/libc-start.c:379:5
#20 0x0000aaaaab5a1ef0 _start (./build/bin/opt+0xb01ef0)
```

Seems like we fail to properly handle fixing up the incoming value for this PHI from the middle block. 
</pre>
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