[llvm] Reapply "[ValueTracking] Propagate sign information out of loop" (PR #182512)

[Antonio Frighetto via llvm-commits]

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@@ -5924,6 +5924,43 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
       }
     }
 
+    // Look for the case of a for loop which has a positive
+    // initial value and is incremented by a squared value.
+    // This will propagate sign information out of such loops.
+    if (P->getNumIncomingValues() != 2)
+      break;
+    for (unsigned i = 0; i < 2; i++) {
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antoniofrighetto wrote:

```suggestion
    for (unsigned I = 0; I < 2; I++) {
```

https://github.com/llvm/llvm-project/pull/182512