From a54d88f97dfeb35e4f6c14e5563ec686e68fd244 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333@gmail.com>
Date: Tue, 15 Oct 2024 13:35:50 +0800
Subject: [PATCH] [APFloat] Fix `APFloat::getOne` (#112308)

`APFloat::APFloat(const fltSemantics &Semantics, integerPart I)`
interprets 'I' as a unsigned integer.
Fix the bug found in
https://github.com/llvm/llvm-project/pull/112113#discussion_r1799744541.
---
 llvm/include/llvm/ADT/APFloat.h    | 5 ++++-
 llvm/unittests/ADT/APFloatTest.cpp | 7 +++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index 6f1e24e5da33a9..97547fb577e0ec 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -1046,7 +1046,10 @@ class APFloat : public APFloatBase {
   ///
   /// \param Negative True iff the number should be negative.
   static APFloat getOne(const fltSemantics &Sem, bool Negative = false) {
-    return APFloat(Sem, Negative ? -1 : 1);
+    APFloat Val(Sem, 1U);
+    if (Negative)
+      Val.changeSign();
+    return Val;
   }
 
   /// Factory for Positive and Negative Infinity.
diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index 6008f00e42a989..665cff9c424594 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -892,6 +892,13 @@ TEST(APFloatTest, Zero) {
   EXPECT_EQ(fcNegZero, APFloat(-0.0).classify());
 }
 
+TEST(APFloatTest, getOne) {
+  EXPECT_EQ(APFloat::getOne(APFloat::IEEEsingle(), false).convertToFloat(),
+            1.0f);
+  EXPECT_EQ(APFloat::getOne(APFloat::IEEEsingle(), true).convertToFloat(),
+            -1.0f);
+}
+
 TEST(APFloatTest, DecimalStringsWithoutNullTerminators) {
   // Make sure that we can parse strings without null terminators.
   // rdar://14323230.