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Fix compilation of Log2(uint64_t) on MSVC 

The _BitScanReverse64 intrinsic only exists when compiling for 64bit.
Replace it by two calls to _BitScanReverse (the 32bit one) when on
32bit.

Bug:
Change-Id: Ie294327ec914b0ca4a73732e4b78c1f2a08f100f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/15321
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
This commit is contained in:
Corentin Wallez 2020-01-22 13:05:16 +00:00 committed by Commit Bot service account
parent 80880ee998
commit 6b66b67f69
1 changed files with 14 additions and 10 deletions
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24
src/common/Math.cpp
View File

@ -15,6 +15,7 @@
#include "common/Math.h"
#include "common/Assert.h"
#include "common/Platform.h"
#include <algorithm>
#include <cmath>
@ -50,28 +51,31 @@ uint32_t Log2(uint32_t value) {
uint32_t Log2(uint64_t value) {
ASSERT(value != 0);
#if defined(DAWN_COMPILER_MSVC)
# if defined(DAWN_PLATFORM_64_BIT)
unsigned long firstBitIndex = 0ul;
unsigned char ret = _BitScanReverse64(&firstBitIndex, value);
ASSERT(ret != 0);
return firstBitIndex;
#else
# else // defined(DAWN_PLATFORM_64_BIT)
unsigned long firstBitIndex = 0ul;
if (_BitScanReverse(&firstBitIndex, value >> 32)) {
return firstBitIndex + 32;
}
unsigned char ret = _BitScanReverse(&firstBitIndex, value & 0xFFFFFFFF);
ASSERT(ret != 0);
return firstBitIndex;
# endif // defined(DAWN_PLATFORM_64_BIT)
#else // defined(DAWN_COMPILER_MSVC)
return 63 - static_cast<uint32_t>(__builtin_clzll(value));
#endif
#endif // defined(DAWN_COMPILER_MSVC)
}
uint64_t NextPowerOfTwo(uint64_t n) {
#if defined(DAWN_COMPILER_MSVC)
if (n <= 1) {
return 1;
}
unsigned long firstBitIndex = 0ul;
unsigned char ret = _BitScanReverse64(&firstBitIndex, n - 1);
ASSERT(ret != 0);
return 1ull << (firstBitIndex + 1);
#else
return n <= 1 ? 1 : 1ull << (64 - __builtin_clzll(n - 1));
#endif
return 1ull << (Log2(n - 1) + 1);
}
bool IsPowerOfTwo(uint64_t n) {