[llvm] [LoopVectorize] In LoopVectorize.cpp start using getSymbolicMaxBackedgeTakenCount (PR #108833)

[Florian Hahn via llvm-commits]

================
@@ -0,0 +1,49 @@
+; REQUIRES: asserts
+; RUN: opt -S -passes=loop-vectorize -enable-vplan-native-path -disable-output -debug 2>&1 < %s | FileCheck %s
+
+; CHECK-LABEL: LV: Found a loop: for.body
+; CHECK: LV: Not vectorizing: Unsupported conditional branch.
+; CHECK: loop not vectorized: loop control flow is not understood by vectorizer
+; CHECK: LV: Not vectorizing: Unsupported outer loop.
+
+ at arr2 = external global [8 x i32], align 16
+ at arr = external global [8 x [8 x i32]], align 16
+
+define i32 @foo(i32 %n) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv21 = phi i64 [ 0, %entry ], [ %indvars.iv.next22, %for.inc ]
----------------
fhahn wrote:

nit here and elsewhere other have slightly more compact names
```suggestion
  %iv21 = phi i64 [ 0, %entry ], [ %indvars.iv.next22, %for.inc ]
```

https://github.com/llvm/llvm-project/pull/108833