[llvm] [SCEV] Consolidate code for proving wrap flags of controlling finite IVs (PR #101404)

[Nikita Popov via llvm-commits]

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@@ -12935,21 +12928,10 @@ ScalarEvolution::howManyLessThans(const SCEV *LHS, const SCEV *RHS,
         Stride = getUMaxExpr(Stride, getOne(Stride->getType()));
       }
     }
-  } else if (!Stride->isOne() && !NoWrap) {
-    auto isUBOnWrap = [&]() {
-      // From no-self-wrap, we need to then prove no-(un)signed-wrap.  This
-      // follows trivially from the fact that every (un)signed-wrapped, but
-      // not self-wrapped value must be LT than the last value before
-      // (un)signed wrap.  Since we know that last value didn't exit, nor
-      // will any smaller one.
-      return canAssumeNoSelfWrap(IV);
-    };
-
+  } else if (!NoWrap) {
     // Avoid proven overflow cases: this will ensure that the backedge taken
-    // count will not generate any unsigned overflow. Relaxed no-overflow
-    // conditions exploit NoWrapFlags, allowing to optimize in presence of
-    // undefined behaviors like the case of C language.
-    if (canIVOverflowOnLT(RHS, Stride, IsSigned) && !isUBOnWrap())
+    // count will not generate any unsigned overflow. .
----------------
nikic wrote:

```suggestion
    // count will not generate any unsigned overflow.
```

https://github.com/llvm/llvm-project/pull/101404