[llvm] [ConstantFold] Fold `log1p` and `log1pf` when the input parameter is a constant value. (PR #112113)

[via llvm-commits]

================
@@ -2394,6 +2395,11 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
       if (!APF.isZero() && TLI->has(Func))
         return ConstantFoldFP(logb, APF, Ty);
       break;
+    case LibFunc_log1p:
+    case LibFunc_log1pf:
+      if (APF > APFloat(APF.getSemantics(), "-1") && TLI->has(Func))
----------------
c8ef wrote:

If I wrote this:

```C++
    case LibFunc_log1pf:
      llvm::errs() << APFloat::getOne(APF.getSemantics(), true) << " " << APFloat(APF.getSemantics(), "-1") << '\n';
      if (APF > APFloat::getOne(APF.getSemantics(), true) && TLI->has(Func))
        return ConstantFoldFP(log1p, APF, Ty);
      break;
```

I got:

```
1.84467441E+19 -1
1.84467441E+19 -1
1.8446744073709552E+19 -1
1.8446744073709552E+19 -1
1.84467441E+19 -1
1.84467441E+19 -1
1.8446744073709552E+19 -1
1.8446744073709552E+19 -1
1.84467441E+19 -1
1.84467441E+19 -1
1.8446744073709552E+19 -1
1.8446744073709552E+19 -1
1.84467441E+19 -1
1.84467441E+19 -1
1.8446744073709552E+19 -1
1.8446744073709552E+19 -1
```

https://github.com/llvm/llvm-project/pull/112113