From 8edac4d81167f4988ee2d92c5368be5466a076ca Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Tue, 30 Jan 2024 13:19:20 -0800
Subject: [PATCH] Use c++20 std::count{l,r}_zero

---
 ConflictSet.cpp | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 11a6f07..b535d8e 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -2,6 +2,7 @@
 #include "Internal.h"
 
 #include <algorithm>
+#include <bit>
 #include <cassert>
 #include <cstdint>
 #include <cstring>
@@ -113,7 +114,7 @@ int getNodeIndex(Node16 *self, uint8_t index) {
 
   // Find the index of the first '1' in the bitfield by counting the leading
   // zeros.
-  return __builtin_ctz(bitfield);
+  return std::countr_zero(bitfield);
 #elif defined(HAS_ARM_NEON)
   // Based on
   // https://community.arm.com/arm-community-blogs/b/infrastructure-solutions-blog/posts/porting-x86-vector-bitmask-optimizations-to-arm-neon
@@ -131,7 +132,7 @@ int getNodeIndex(Node16 *self, uint8_t index) {
       vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(results, 4)), 0) & mask;
   if (bitfield == 0)
     return -1;
-  return __builtin_ctzll(bitfield) / 4;
+  return std::countr_zero(bitfield) / 4;
 #else
   for (int i = 0; i < self->numChildren; ++i) {
     if (self->index[i] == index) {
@@ -151,7 +152,7 @@ int firstNonNeg1(const int8_t x[16]) {
   uint32_t bitfield = _mm_movemask_epi8(results) ^ 0xffff;
   if (bitfield == 0)
     return -1;
-  return __builtin_ctz(bitfield);
+  return std::countr_zero(bitfield);
 }
 
 int lastNonNeg1(const int8_t x[16]) {
@@ -162,7 +163,7 @@ int lastNonNeg1(const int8_t x[16]) {
   uint32_t bitfield = _mm_movemask_epi8(results) ^ 0xffff;
   if (bitfield == 0)
     return -1;
-  return 31 - __builtin_clz(bitfield);
+  return 31 - std::countl_zero(bitfield);
 }
 #endif
 
@@ -175,7 +176,7 @@ int firstNonNeg1(const int8_t x[16]) {
       ~vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(results, 4)), 0);
   if (bitfield == 0)
     return -1;
-  return __builtin_ctzll(bitfield) / 4;
+  return std::countr_zero(bitfield) / 4;
 }
 
 int lastNonNeg1(const int8_t x[16]) {
@@ -186,7 +187,7 @@ int lastNonNeg1(const int8_t x[16]) {
       ~vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(results, 4)), 0);
   if (bitfield == 0)
     return -1;
-  return 15 - __builtin_clzll(bitfield) / 4;
+  return 15 - std::countl_zero(bitfield) / 4;
 }
 #endif
 
@@ -262,7 +263,7 @@ int getChildGeq(Node *self, int child) {
     __m128i results = _mm_cmpeq_epi8(key_vec, _mm_min_epu8(key_vec, indices));
     int mask = (1 << self16->numChildren) - 1;
     int bitfield = _mm_movemask_epi8(results) & mask;
-    int result = bitfield == 0 ? -1 : self16->index[__builtin_ctz(bitfield)];
+    int result = bitfield == 0 ? -1 : self16->index[std::countr_zero(bitfield)];
     assert(result == [&]() -> int {
       for (int i = 0; i < self16->numChildren; ++i) {
         if (self16->index[i] >= child) {
@@ -287,7 +288,7 @@ int getChildGeq(Node *self, int child) {
             0) &
         mask;
     int simd =
-        bitfield == 0 ? -1 : self16->index[__builtin_ctzll(bitfield) / 4];
+        bitfield == 0 ? -1 : self16->index[std::countr_zero(bitfield) / 4];
     assert(simd == [&]() -> int {
       for (int i = 0; i < self->numChildren; ++i) {
         if (self16->index[i] >= child) {
@@ -366,7 +367,7 @@ int getChildLeq(Node *self, int child) {
     int mask = (1 << self16->numChildren) - 1;
     int bitfield = _mm_movemask_epi8(results) & mask;
     int result =
-        bitfield == 0 ? -1 : self16->index[31 - __builtin_clz(bitfield)];
+        bitfield == 0 ? -1 : self16->index[31 - std::countl_zero(bitfield)];
     assert(result == [&]() -> int {
       for (int i = self16->numChildren - 1; i >= 0; --i) {
         if (self16->index[i] <= child) {
@@ -391,7 +392,7 @@ int getChildLeq(Node *self, int child) {
             0) &
         mask;
     int simd =
-        bitfield == 0 ? -1 : self16->index[15 - __builtin_clzll(bitfield) / 4];
+        bitfield == 0 ? -1 : self16->index[15 - std::countl_zero(bitfield) / 4];
     assert(simd == [&]() -> int {
       for (int i = self->numChildren - 1; i >= 0; --i) {
         if (self16->index[i] <= child) {