[clang] [clang][Sema] Move computing enum width and type to a separate function (PR #120965)

[via cfe-commits]

================
@@ -20099,73 +20095,12 @@ void Sema::ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
       BestPromotionType = BestType;
 
     BestWidth = Context.getIntWidth(BestType);
-  }
-  else if (NumNegativeBits) {
-    // If there is a negative value, figure out the smallest integer type (of
-    // int/long/longlong) that fits.
-    // If it's packed, check also if it fits a char or a short.
-    if (Packed && NumNegativeBits <= CharWidth && NumPositiveBits < CharWidth) {
-      BestType = Context.SignedCharTy;
-      BestWidth = CharWidth;
-    } else if (Packed && NumNegativeBits <= ShortWidth &&
-               NumPositiveBits < ShortWidth) {
-      BestType = Context.ShortTy;
-      BestWidth = ShortWidth;
-    } else if (NumNegativeBits <= IntWidth && NumPositiveBits < IntWidth) {
-      BestType = Context.IntTy;
-      BestWidth = IntWidth;
-    } else {
-      BestWidth = Context.getTargetInfo().getLongWidth();
-
-      if (NumNegativeBits <= BestWidth && NumPositiveBits < BestWidth) {
-        BestType = Context.LongTy;
-      } else {
-        BestWidth = Context.getTargetInfo().getLongLongWidth();
-
-        if (NumNegativeBits > BestWidth || NumPositiveBits >= BestWidth)
-          Diag(Enum->getLocation(), diag::ext_enum_too_large);
-        BestType = Context.LongLongTy;
-      }
-    }
-    BestPromotionType = (BestWidth <= IntWidth ? Context.IntTy : BestType);
   } else {
-    // If there is no negative value, figure out the smallest type that fits
-    // all of the enumerator values.
-    // If it's packed, check also if it fits a char or a short.
-    if (Packed && NumPositiveBits <= CharWidth) {
-      BestType = Context.UnsignedCharTy;
-      BestPromotionType = Context.IntTy;
-      BestWidth = CharWidth;
-    } else if (Packed && NumPositiveBits <= ShortWidth) {
-      BestType = Context.UnsignedShortTy;
-      BestPromotionType = Context.IntTy;
-      BestWidth = ShortWidth;
-    } else if (NumPositiveBits <= IntWidth) {
-      BestType = Context.UnsignedIntTy;
-      BestWidth = IntWidth;
-      BestPromotionType
-        = (NumPositiveBits == BestWidth || !getLangOpts().CPlusPlus)
-                           ? Context.UnsignedIntTy : Context.IntTy;
-    } else if (NumPositiveBits <=
-               (BestWidth = Context.getTargetInfo().getLongWidth())) {
-      BestType = Context.UnsignedLongTy;
-      BestPromotionType
-        = (NumPositiveBits == BestWidth || !getLangOpts().CPlusPlus)
-                           ? Context.UnsignedLongTy : Context.LongTy;
-    } else {
-      BestWidth = Context.getTargetInfo().getLongLongWidth();
-      if (NumPositiveBits > BestWidth) {
-        // This can happen with bit-precise integer types, but those are not
-        // allowed as the type for an enumerator per C23 6.7.2.2p4 and p12.
-        // FIXME: GCC uses __int128_t and __uint128_t for cases that fit within
-        // a 128-bit integer, we should consider doing the same.
-        Diag(Enum->getLocation(), diag::ext_enum_too_large);
-      }
-      BestType = Context.UnsignedLongLongTy;
-      BestPromotionType
-        = (NumPositiveBits == BestWidth || !getLangOpts().CPlusPlus)
-                           ? Context.UnsignedLongLongTy : Context.LongLongTy;
-    }
+    const bool EnumTooLarge = Context.computeBestEnumTypes(
----------------
Sirraide wrote:

```suggestion
    bool EnumTooLarge = Context.computeBestEnumTypes(
```

https://github.com/llvm/llvm-project/pull/120965