From 5bb8ead0a7115d7f19f92f02145d8d39705b0296 Mon Sep 17 00:00:00 2001
From: Xiaodi Wu <13952+xwu@users.noreply.github.com>
Date: Thu, 26 Oct 2023 16:25:11 -0400
Subject: [PATCH 1/2] [test/Prototypes] Fix DoubleWidth think-o that trips an
 assert

---
 test/Prototypes/DoubleWidth.swift.gyb | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/test/Prototypes/DoubleWidth.swift.gyb b/test/Prototypes/DoubleWidth.swift.gyb
index 7b6cf0dfdcfe7..e08f440c549e8 100644
--- a/test/Prototypes/DoubleWidth.swift.gyb
+++ b/test/Prototypes/DoubleWidth.swift.gyb
@@ -702,8 +702,9 @@ extension DoubleWidth : UnsignedInteger where Base : UnsignedInteger {
     let rhs = rhs &<< shift
     let high = (lhs &>> (Magnitude.bitWidth &- shift)).low
     let lhs = lhs &<< shift
-    let (quotient, remainder) =
-      Magnitude._divide((high, lhs.high, lhs.low), by: rhs)
+    let (quotient, remainder) = high == (0 as Low)
+      ? (1, lhs &- rhs)
+      : Magnitude._divide((high, lhs.high, lhs.low), by: rhs)
     return (Magnitude(0, quotient), remainder &>> shift)
   }
 }
@@ -805,6 +806,12 @@ dwTests.test("Arithmetic/unsigned") {
 
   expectEqual(x % 3, 1)
   expectEqual(x % y, x)
+
+  do {
+    let lhs = DoubleWidth<UInt8>((high: 0b0011_0000, low: 0))
+    let rhs = DoubleWidth<UInt8>((high: 0b0010_0000, low: 0))
+    expectEqual(lhs % rhs, 4096)
+  }
 }
 
 dwTests.test("Arithmetic/signed") {

From c6eba6b1615ad441afcb6ac7ddecf2105bb41160 Mon Sep 17 00:00:00 2001
From: Xiaodi Wu <13952+xwu@users.noreply.github.com>
Date: Mon, 30 Oct 2023 16:25:52 -0400
Subject: [PATCH 2/2] [test/Prototypes] Fix second DoubleWidth think-o that
 trips an assert

---
 test/Prototypes/DoubleWidth.swift.gyb | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/test/Prototypes/DoubleWidth.swift.gyb b/test/Prototypes/DoubleWidth.swift.gyb
index e08f440c549e8..4da689872e68c 100644
--- a/test/Prototypes/DoubleWidth.swift.gyb
+++ b/test/Prototypes/DoubleWidth.swift.gyb
@@ -699,8 +699,8 @@ extension DoubleWidth : UnsignedInteger where Base : UnsignedInteger {
 
     // Left shift both rhs and lhs, then divide and right shift the remainder.
     let shift = rhs.leadingZeroBitCount
+    let high = (lhs >> (Magnitude.bitWidth &- shift)).low
     let rhs = rhs &<< shift
-    let high = (lhs &>> (Magnitude.bitWidth &- shift)).low
     let lhs = lhs &<< shift
     let (quotient, remainder) = high == (0 as Low)
       ? (1, lhs &- rhs)
@@ -812,6 +812,16 @@ dwTests.test("Arithmetic/unsigned") {
     let rhs = DoubleWidth<UInt8>((high: 0b0010_0000, low: 0))
     expectEqual(lhs % rhs, 4096)
   }
+  do {
+    let lhs = DoubleWidth<UInt64>((high: 0xa0c7d7165cf01386, low: 0xbf3f66a93056143f))
+    let rhs = DoubleWidth<UInt64>((high: 0x9ac3a19b1e7d6b83, low: 0x513929792d588736))
+    expectEqual(String(lhs % rhs), "7997221894243298914179865336050715913")
+  }
+  do {
+    let lhs = DoubleWidth<UInt64>((high: 0xea8a9116b7af33b7, low: 0x3d9d6779ddd22ca3))
+    let rhs = DoubleWidth<UInt64>((high: 0xc3673efc7f1f37cc, low: 0x312f661057d0ba94))
+    expectEqual(String(lhs % rhs), "52023287460685389410162512181093036559")
+  }
 }
 
 dwTests.test("Arithmetic/signed") {