[llvm] ADT: Switch to a raw pointer for DoubleAPFloat::Floats. (PR #129981)

[Peter Collingbourne via llvm-commits]

https://github.com/pcc created https://github.com/llvm/llvm-project/pull/129981

In order for the union APFloat::Storage to permit access to the
semantics field when another union member is stored there, all members
of Storage must be standard layout. This is not necessarily the case
for DoubleAPFloat which may be non-standard layout because there is no
requirement that its std::unique_ptr member is standard layout. Fix this
by converting Floats to a raw pointer.


>From d45e3881e15ec032e431d5f9414ee91c15802616 Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <pcc at google.com>
Date: Wed, 5 Mar 2025 19:39:22 -0800
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Created using spr 1.3.6-beta.1
---
 llvm/include/llvm/ADT/APFloat.h | 7 ++++++-
 llvm/lib/Support/APFloat.cpp    | 3 ++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index 70fbf2059841e..9962c878cfbfc 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -805,7 +805,7 @@ IEEEFloat frexp(const IEEEFloat &Val, int &Exp, roundingMode RM);
 class DoubleAPFloat final {
   // Note: this must be the first data member.
   const fltSemantics *Semantics;
-  std::unique_ptr<APFloat[]> Floats;
+  APFloat *Floats;
 
   opStatus addImpl(const APFloat &a, const APFloat &aa, const APFloat &c,
                    const APFloat &cc, roundingMode RM);
@@ -821,6 +821,7 @@ class DoubleAPFloat final {
   DoubleAPFloat(const fltSemantics &S, APFloat &&First, APFloat &&Second);
   DoubleAPFloat(const DoubleAPFloat &RHS);
   DoubleAPFloat(DoubleAPFloat &&RHS);
+  ~DoubleAPFloat();
 
   DoubleAPFloat &operator=(const DoubleAPFloat &RHS);
   inline DoubleAPFloat &operator=(DoubleAPFloat &&RHS);
@@ -1659,6 +1660,10 @@ const APFloat &DoubleAPFloat::getFirst() const { return Floats[0]; }
 APFloat &DoubleAPFloat::getSecond() { return Floats[1]; }
 const APFloat &DoubleAPFloat::getSecond() const { return Floats[1]; }
 
+inline DoubleAPFloat::~DoubleAPFloat() {
+  delete[] Floats;
+}
+
 } // namespace detail
 
 } // namespace llvm
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index cbee7f48b8773..cfc3c3b4974c5 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -4876,8 +4876,9 @@ DoubleAPFloat::DoubleAPFloat(const DoubleAPFloat &RHS)
 }
 
 DoubleAPFloat::DoubleAPFloat(DoubleAPFloat &&RHS)
-    : Semantics(RHS.Semantics), Floats(std::move(RHS.Floats)) {
+    : Semantics(RHS.Semantics), Floats(RHS.Floats) {
   RHS.Semantics = &semBogus;
+  RHS.Floats = nullptr;
   assert(Semantics == &semPPCDoubleDouble);
 }