[llvm] [KnownFPClass] Fix `KnownFPClass::log` deductions for ppcf128 (PR #223296)

[Eric Ross via llvm-commits]

================
@@ -327,8 +327,12 @@ struct KnownFPClass {
   sqrt(const KnownFPClass &Src, DenormalMode Mode = DenormalMode::getDynamic());
 
   /// Propagate known class for log/log2/log10
+  ///
+  /// IsKnownNeverMultiUnitFPType if this is known to never be for a multi-unit
+  /// floating-point type.
   LLVM_ABI static KnownFPClass
-  log(const KnownFPClass &Src, DenormalMode Mode = DenormalMode::getDynamic());
+  log(const KnownFPClass &Src, DenormalMode Mode = DenormalMode::getDynamic(),
+      bool IsKnownNeverMultiUnitFPType = false);
----------------
ZERICO2005 wrote:

Waiting on https://github.com/llvm/llvm-project/pull/219700 to resolve how `PPCDoubleDouble` detection will be implemented.


https://github.com/llvm/llvm-project/pull/223296