[dawn] Replace `ScanForward()` with `std::countr_zero()` in C++20
Bug: 343500108
Change-Id: I8fd817c6a5f80a0a3f34c0a208f27f3efff6ba0e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/240654
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
Reviewed-by: Loko Kung <lokokung@google.com>
diff --git a/src/dawn/common/BitSetRangeIterator.h b/src/dawn/common/BitSetRangeIterator.h
index 6447751..d44ad3c 100644
--- a/src/dawn/common/BitSetRangeIterator.h
+++ b/src/dawn/common/BitSetRangeIterator.h
@@ -28,6 +28,7 @@
#ifndef SRC_DAWN_COMMON_BITSETRANGEITERATOR_H_
#define SRC_DAWN_COMMON_BITSETRANGEITERATOR_H_
+#include <bit>
#include <bitset>
#include <limits>
#include <utility>
@@ -132,7 +133,8 @@
mBits >>= kBitsPerWord;
}
- size_t nextBit = ScanForward(static_cast<uint64_t>((mBits & wordMask).to_ullong()));
+ size_t nextBit = static_cast<size_t>(
+ std::countr_zero(static_cast<uint64_t>((mBits & wordMask).to_ullong())));
mBits >>= nextBit;
return offset + nextBit;
}
diff --git a/src/dawn/common/Math.h b/src/dawn/common/Math.h
index 89f1d82..6a055d8 100644
--- a/src/dawn/common/Math.h
+++ b/src/dawn/common/Math.h
@@ -169,38 +169,7 @@
}
// The following functions are defined in the header so they may be inlined.
-
#if DAWN_COMPILER_IS(MSVC)
-// Return the index of the least significant bit set. Indexing is such that bit 0 is the least
-// significant bit. Implemented for different bit widths on different platforms.
-inline uint32_t ScanForward(uint32_t bits) {
- DAWN_ASSERT(bits != 0u);
- // NOLINTNEXTLINE(runtime/int)
- unsigned long firstBitIndex = 0ul;
- uint8_t ret = _BitScanForward(&firstBitIndex, bits);
- DAWN_ASSERT(ret != 0u);
- return static_cast<uint32_t>(firstBitIndex);
-}
-
-inline uint32_t ScanForward(uint64_t bits) {
- DAWN_ASSERT(bits != 0u);
- // NOLINTNEXTLINE(runtime/int)
- unsigned long firstBitIndex = 0ul;
-#if DAWN_PLATFORM_IS(64_BIT)
- uint8_t ret = _BitScanForward64(&firstBitIndex, bits);
-#else
- uint8_t ret;
- if (static_cast<uint32_t>(bits) == 0) {
- ret = _BitScanForward(&firstBitIndex, static_cast<uint32_t>(bits >> 32));
- firstBitIndex += 32ul;
- } else {
- ret = _BitScanForward(&firstBitIndex, static_cast<uint32_t>(bits));
- }
-#endif // DAWN_PLATFORM_IS(64_BIT)
- DAWN_ASSERT(ret != 0u);
- return firstBitIndex;
-}
-
// Return the index of the most significant bit set. Indexing is such that bit 0 is the least
// significant bit.
inline uint32_t ScanReverse(uint32_t bits) {
@@ -232,22 +201,6 @@
}
#else // DAWN_COMPILER_IS(MSVC)
-inline uint32_t ScanForward(uint32_t bits) {
- DAWN_ASSERT(bits != 0u);
- return static_cast<uint32_t>(__builtin_ctz(bits));
-}
-
-inline uint32_t ScanForward(uint64_t bits) {
- DAWN_ASSERT(bits != 0u);
-#if DAWN_PLATFORM_IS(64_BIT)
- return static_cast<uint32_t>(__builtin_ctzll(bits));
-#else
- return static_cast<uint32_t>(static_cast<uint32_t>(bits) == 0
- ? __builtin_ctz(static_cast<uint32_t>(bits >> 32)) + 32
- : __builtin_ctz(static_cast<uint32_t>(bits)));
-#endif // DAWN_PLATFORM_IS(64_BIT)
-}
-
inline uint32_t ScanReverse(uint32_t bits) {
DAWN_ASSERT(bits != 0u);
return static_cast<uint32_t>((sizeof(uint32_t) * CHAR_BIT) - 1 - __builtin_clz(bits));
@@ -269,14 +222,6 @@
#endif // !DAWN_COMPILER_IS(MSVC)
-inline uint32_t ScanForward(uint8_t bits) {
- return ScanForward(static_cast<uint32_t>(bits));
-}
-
-inline uint32_t ScanForward(uint16_t bits) {
- return ScanForward(static_cast<uint32_t>(bits));
-}
-
inline uint32_t ScanReverse(uint8_t bits) {
return ScanReverse(static_cast<uint32_t>(bits));
}
diff --git a/src/dawn/common/ityp_bitset.h b/src/dawn/common/ityp_bitset.h
index 22ac20b..190cc38 100644
--- a/src/dawn/common/ityp_bitset.h
+++ b/src/dawn/common/ityp_bitset.h
@@ -28,6 +28,7 @@
#ifndef SRC_DAWN_COMMON_ITYP_BITSET_H_
#define SRC_DAWN_COMMON_ITYP_BITSET_H_
+#include <bit>
#include <bitset>
#include <limits>
@@ -81,7 +82,7 @@
if (mBits == 0) {
return 0;
}
- return ScanForward(mBits);
+ return std::countr_zero(mBits);
}
template <typename Index, size_t N>
@@ -138,7 +139,7 @@
while (mOffset < N) {
uint64_t wordBits = static_cast<uint64_t>((mBits & wordMask).to_ullong());
if (wordBits != 0ull) {
- return ScanForward(wordBits) + mOffset;
+ return std::countr_zero(wordBits) + mOffset;
}
mBits >>= kBitsPerWord;
diff --git a/src/dawn/native/AttachmentState.cpp b/src/dawn/native/AttachmentState.cpp
index 59c786a..492ec90 100644
--- a/src/dawn/native/AttachmentState.cpp
+++ b/src/dawn/native/AttachmentState.cpp
@@ -27,6 +27,8 @@
#include "dawn/native/AttachmentState.h"
+#include <bit>
+
#include "dawn/common/Enumerator.h"
#include "dawn/common/ityp_span.h"
#include "dawn/native/ChainUtils.h"
@@ -328,8 +330,8 @@
auto availableSlots = ~mColorAttachmentsSet;
for (size_t i = 0; i < mStorageAttachmentSlots.size(); i++) {
DAWN_ASSERT(!availableSlots.none());
- auto slot = ColorAttachmentIndex(
- uint8_t(ScanForward(static_cast<uint32_t>(availableSlots.to_ulong()))));
+ auto slot = ColorAttachmentIndex(static_cast<uint8_t>(
+ std::countr_zero(static_cast<uint32_t>(availableSlots.to_ulong()))));
availableSlots.reset(slot);
result[i] = slot;
}
diff --git a/src/dawn/tests/unittests/MathTests.cpp b/src/dawn/tests/unittests/MathTests.cpp
index 063b93b..12a3dca 100644
--- a/src/dawn/tests/unittests/MathTests.cpp
+++ b/src/dawn/tests/unittests/MathTests.cpp
@@ -53,49 +53,6 @@
namespace dawn {
namespace {
-// Tests for ScanForward
-TEST(Math, ScanForward) {
- // 8-bit
- // Test extrema
- ASSERT_EQ(ScanForward(uint8_t(1)), 0u);
- ASSERT_EQ(ScanForward(uint8_t(0x80)), 7u);
-
- // Test with more than one bit set.
- ASSERT_EQ(ScanForward(uint8_t(64)), 6u);
- ASSERT_EQ(ScanForward(uint8_t(64 + 32)), 5u);
- ASSERT_EQ(ScanForward(uint8_t(128 + 64 + 32)), 5u);
-
- // 16-bit
- // Test extrema
- ASSERT_EQ(ScanForward(uint16_t(1)), 0u);
- ASSERT_EQ(ScanForward(uint16_t(0x8000)), 15u);
-
- // Test with more than one bit set.
- ASSERT_EQ(ScanForward(uint16_t(256)), 8u);
- ASSERT_EQ(ScanForward(uint16_t(256 + 32)), 5u);
- ASSERT_EQ(ScanForward(uint16_t(1024u + 256 + 32)), 5u);
-
- // 32-bit
- // Test extrema
- ASSERT_EQ(ScanForward(1u), 0u);
- ASSERT_EQ(ScanForward(0x80000000u), 31u);
-
- // Test with more than one bit set.
- ASSERT_EQ(ScanForward(256u), 8u);
- ASSERT_EQ(ScanForward(256u + 32u), 5u);
- ASSERT_EQ(ScanForward(1024u + 256u + 32u), 5u);
-
- // 64-bit
- // Test extrema
- ASSERT_EQ(ScanForward(uint64_t(1)), 0u);
- ASSERT_EQ(ScanForward(uint64_t(0x8000000000000000ull)), 63u);
-
- // Test with more than one bit set.
- ASSERT_EQ(ScanForward(uint64_t(256ull)), 8u);
- ASSERT_EQ(ScanForward(uint64_t(256ull + 32ull)), 5u);
- ASSERT_EQ(ScanForward(uint64_t(0x800000000ull + 256ull + 32ull)), 5u);
-}
-
// Tests for ScanReverse
TEST(Math, ScanReverse) {
// 8-bit
