[APFloat] Outline special member functions (#164073)

As discussed in
llvm/llvm-project#111544 (comment),
large special member functions in APFloat prevent function inlining and
cause compile-time regression. This patch moves them into the cpp file.

Compile-time improvement (-0.1%):
https://llvm-compile-time-tracker.com/compare.php?from=0f68dc6cffd93954188f73bff8aced93aab63687&to=d3105c0860920651a7e939346e67c040776b2278&stat=instructions:u

Author: dtcxzyw

llvm/include/llvm/ADT/APFloat.h

@@ -967,69 +967,11 @@ class APFloat : public APFloatBase {
       llvm_unreachable("Unexpected semantics");
     }
 
-    ~Storage() {
-      if (usesLayout<IEEEFloat>(*semantics)) {
-        IEEE.~IEEEFloat();
-        return;
-      }
-      if (usesLayout<DoubleAPFloat>(*semantics)) {
-        Double.~DoubleAPFloat();
-        return;
-      }
-      llvm_unreachable("Unexpected semantics");
-    }
-
-    Storage(const Storage &RHS) {
-      if (usesLayout<IEEEFloat>(*RHS.semantics)) {
-        new (this) IEEEFloat(RHS.IEEE);
-        return;
-      }
-      if (usesLayout<DoubleAPFloat>(*RHS.semantics)) {
-        new (this) DoubleAPFloat(RHS.Double);
-        return;
-      }
-      llvm_unreachable("Unexpected semantics");
-    }
-
-    Storage(Storage &&RHS) {
-      if (usesLayout<IEEEFloat>(*RHS.semantics)) {
-        new (this) IEEEFloat(std::move(RHS.IEEE));
-        return;
-      }
-      if (usesLayout<DoubleAPFloat>(*RHS.semantics)) {
-        new (this) DoubleAPFloat(std::move(RHS.Double));
-        return;
-      }
-      llvm_unreachable("Unexpected semantics");
-    }
-
-    Storage &operator=(const Storage &RHS) {
-      if (usesLayout<IEEEFloat>(*semantics) &&
-          usesLayout<IEEEFloat>(*RHS.semantics)) {
-        IEEE = RHS.IEEE;
-      } else if (usesLayout<DoubleAPFloat>(*semantics) &&
-                 usesLayout<DoubleAPFloat>(*RHS.semantics)) {
-        Double = RHS.Double;
-      } else if (this != &RHS) {
-        this->~Storage();
-        new (this) Storage(RHS);
-      }
-      return *this;
-    }
-
-    Storage &operator=(Storage &&RHS) {
-      if (usesLayout<IEEEFloat>(*semantics) &&
-          usesLayout<IEEEFloat>(*RHS.semantics)) {
-        IEEE = std::move(RHS.IEEE);
-      } else if (usesLayout<DoubleAPFloat>(*semantics) &&
-                 usesLayout<DoubleAPFloat>(*RHS.semantics)) {
-        Double = std::move(RHS.Double);
-      } else if (this != &RHS) {
-        this->~Storage();
-        new (this) Storage(std::move(RHS));
-      }
-      return *this;
-    }
+    LLVM_ABI ~Storage();
+    LLVM_ABI Storage(const Storage &RHS);
+    LLVM_ABI Storage(Storage &&RHS);
+    LLVM_ABI Storage &operator=(const Storage &RHS);
+    LLVM_ABI Storage &operator=(Storage &&RHS);
   } U;
 
   template <typename T> static bool usesLayout(const fltSemantics &Semantics) {

llvm/lib/Support/APFloat.cpp

@@ -6165,6 +6165,70 @@ float APFloat::convertToFloat() const {
   return Temp.getIEEE().convertToFloat();
 }
 
+APFloat::Storage::~Storage() {
+  if (usesLayout<IEEEFloat>(*semantics)) {
+    IEEE.~IEEEFloat();
+    return;
+  }
+  if (usesLayout<DoubleAPFloat>(*semantics)) {
+    Double.~DoubleAPFloat();
+    return;
+  }
+  llvm_unreachable("Unexpected semantics");
+}
+
+APFloat::Storage::Storage(const APFloat::Storage &RHS) {
+  if (usesLayout<IEEEFloat>(*RHS.semantics)) {
+    new (this) IEEEFloat(RHS.IEEE);
+    return;
+  }
+  if (usesLayout<DoubleAPFloat>(*RHS.semantics)) {
+    new (this) DoubleAPFloat(RHS.Double);
+    return;
+  }
+  llvm_unreachable("Unexpected semantics");
+}
+
+APFloat::Storage::Storage(APFloat::Storage &&RHS) {
+  if (usesLayout<IEEEFloat>(*RHS.semantics)) {
+    new (this) IEEEFloat(std::move(RHS.IEEE));
+    return;
+  }
+  if (usesLayout<DoubleAPFloat>(*RHS.semantics)) {
+    new (this) DoubleAPFloat(std::move(RHS.Double));
+    return;
+  }
+  llvm_unreachable("Unexpected semantics");
+}
+
+APFloat::Storage &APFloat::Storage::operator=(const APFloat::Storage &RHS) {
+  if (usesLayout<IEEEFloat>(*semantics) &&
+      usesLayout<IEEEFloat>(*RHS.semantics)) {
+    IEEE = RHS.IEEE;
+  } else if (usesLayout<DoubleAPFloat>(*semantics) &&
+             usesLayout<DoubleAPFloat>(*RHS.semantics)) {
+    Double = RHS.Double;
+  } else if (this != &RHS) {
+    this->~Storage();
+    new (this) Storage(RHS);
+  }
+  return *this;
+}
+
+APFloat::Storage &APFloat::Storage::operator=(APFloat::Storage &&RHS) {
+  if (usesLayout<IEEEFloat>(*semantics) &&
+      usesLayout<IEEEFloat>(*RHS.semantics)) {
+    IEEE = std::move(RHS.IEEE);
+  } else if (usesLayout<DoubleAPFloat>(*semantics) &&
+             usesLayout<DoubleAPFloat>(*RHS.semantics)) {
+    Double = std::move(RHS.Double);
+  } else if (this != &RHS) {
+    this->~Storage();
+    new (this) Storage(std::move(RHS));
+  }
+  return *this;
+}
+
 } // namespace llvm
 
 #undef APFLOAT_DISPATCH_ON_SEMANTICS