From 1e6c90a167d7b31eff476debd68023ad485881e1 Mon Sep 17 00:00:00 2001
From: Charlie Barto <chbarto@microsoft.com>
Date: Mon, 11 Apr 2022 15:33:36 -0700
Subject: [PATCH 1/3] Fix countl_zero on arm64 to properly subtract the zeros
 resulting from widening

---
 stl/inc/bit | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/stl/inc/bit b/stl/inc/bit
index fe1d267f7fd..8f7ca14481f 100644
--- a/stl/inc/bit
+++ b/stl/inc/bit
@@ -253,9 +253,11 @@ _NODISCARD int _Checked_arm_arm64_countl_zero(const _Ty _Val) noexcept {
     }
 #else // ^^^ workaround / no workaround vvv
     if constexpr (_Digits <= 32) {
-        return static_cast<int>(_CountLeadingZeros(_Val));
+        return static_cast<int>(_CountLeadingZeros(_Val))
+            - (numeric_limits<unsigned long>::digits - _Digits);
     } else {
-        return static_cast<int>(_CountLeadingZeros64(_Val));
+        return static_cast<int>(_CountLeadingZeros64(_Val))
+            - (numeric_limits<unsigned long long>::digits - _Digits);
     }
 #endif // TRANSITION, GH-1586
 }

From 0552a200679f5177fd6e54a3fb6c54d49b1a07f7 Mon Sep 17 00:00:00 2001
From: Charlie Barto <chbarto@microsoft.com>
Date: Mon, 11 Apr 2022 15:41:32 -0700
Subject: [PATCH 2/3] clang-format

---
 stl/inc/bit | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/stl/inc/bit b/stl/inc/bit
index 8f7ca14481f..b19b6256ca0 100644
--- a/stl/inc/bit
+++ b/stl/inc/bit
@@ -253,11 +253,9 @@ _NODISCARD int _Checked_arm_arm64_countl_zero(const _Ty _Val) noexcept {
     }
 #else // ^^^ workaround / no workaround vvv
     if constexpr (_Digits <= 32) {
-        return static_cast<int>(_CountLeadingZeros(_Val))
-            - (numeric_limits<unsigned long>::digits - _Digits);
+        return static_cast<int>(_CountLeadingZeros(_Val)) - (numeric_limits<unsigned long>::digits - _Digits);
     } else {
-        return static_cast<int>(_CountLeadingZeros64(_Val))
-            - (numeric_limits<unsigned long long>::digits - _Digits);
+        return static_cast<int>(_CountLeadingZeros64(_Val)) - (numeric_limits<unsigned long long>::digits - _Digits);
     }
 #endif // TRANSITION, GH-1586
 }

From 5ef76e0902754cad385f3da4559cfc7a92590b3a Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Wed, 13 Apr 2022 22:28:48 -0700
Subject: [PATCH 3/3] Remove unnecessary code (thanks AlexGuteniev).

---
 stl/inc/bit | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stl/inc/bit b/stl/inc/bit
index b19b6256ca0..eeed2dcd357 100644
--- a/stl/inc/bit
+++ b/stl/inc/bit
@@ -255,7 +255,7 @@ _NODISCARD int _Checked_arm_arm64_countl_zero(const _Ty _Val) noexcept {
     if constexpr (_Digits <= 32) {
         return static_cast<int>(_CountLeadingZeros(_Val)) - (numeric_limits<unsigned long>::digits - _Digits);
     } else {
-        return static_cast<int>(_CountLeadingZeros64(_Val)) - (numeric_limits<unsigned long long>::digits - _Digits);
+        return static_cast<int>(_CountLeadingZeros64(_Val));
     }
 #endif // TRANSITION, GH-1586
 }