TEST(BitsTest_CountZeros, Constants) {
ASSERT_EQUALS(countLeadingZeros64(0ull), 64);
ASSERT_EQUALS(countTrailingZeros64(0ull), 64);
ASSERT_EQUALS(countLeadingZeros64(0x1234ull), 64 - 13);
ASSERT_EQUALS(countTrailingZeros64(0x1234ull), 2);
ASSERT_EQUALS(countLeadingZeros64(0x1234ull << 32), 32 - 13);
ASSERT_EQUALS(countTrailingZeros64(0x1234ull << 32), 2 + 32);
ASSERT_EQUALS(countLeadingZeros64((0x1234ull << 32) | 0x1234ull), 32 - 13);
ASSERT_EQUALS(countTrailingZeros64((0x1234ull << 32) | 0x1234ull), 2);
}
TEST(BitsTest_CountZeros, EachBit) {
for (int i = 0; i < 64; i++) {
unsigned long long x = 1ULL << i;
ASSERT_EQUALS(countLeadingZeros64(x), 64 - 1 - i);
ASSERT_EQUALS(countTrailingZeros64(x), i);
}
}
// Computes the log base 2 of value, and checks for cases of split buckets.
int OperationLatencyHistogram::_getBucket(uint64_t value) {
// Zero is a special case since log(0) is undefined.
if (value == 0) {
return 0;
}
int log2 = 63 - countLeadingZeros64(value);
// Half splits occur in range [2^11, 2^21) giving 10 extra buckets.
if (log2 < 11) {
return log2;
} else if (log2 < 21) {
int extra = log2 - 11;
// Split value boundary is at (2^n + 2^(n+1))/2 = 2^n + 2^(n-1).
// Which corresponds to (1ULL << log2) | (1ULL << (log2 - 1))
// Which is equivalent to the following:
uint64_t splitBoundary = 3ULL << (log2 - 1);
if (value >= splitBoundary) {
extra++;
}
return log2 + extra;
} else {
// Add all of the extra 10 buckets.
return std::min(log2 + 10, kMaxBuckets - 1);
}
}
static float64
normalizeRoundAndPackFloat64 (flag zSign, int16 zExp, bits64 zSig)
{
int8 shiftCount;
shiftCount = countLeadingZeros64 (zSig) - 1;
return roundAndPackFloat64 (zSign, zExp - shiftCount, zSig << shiftCount);
}
static void
normalizeFloat64Subnormal (bits64 aSig, int16 * zExpPtr, bits64 * zSigPtr)
{
int8 shiftCount;
shiftCount = countLeadingZeros64 (aSig) - 11;
*zSigPtr = aSig << shiftCount;
*zExpPtr = 1 - shiftCount;
}
static void addFeature( List< ShaderFeature >& features, const string& name, uint32 maxValue )
{
const ShaderFeature* pLastFeature = nullptr;
if ( features.getCount() > 0u )
{
pLastFeature = &features.getLast();
}
ShaderFeature feature;
feature.name = name;
feature.bitCount = uint32( 64u - countLeadingZeros64( maxValue ) );
feature.maxValue = maxValue;
if ( pLastFeature != nullptr )
{
feature.startBit = pLastFeature->startBit + pLastFeature->bitCount;
}
else
{
feature.startBit = 0u;
}
features.add( feature );
}
void normalizeFloatx80Subnormal(UINT64 aSig, INT32 *zExpPtr, UINT64 *zSigPtr)
{
int shiftCount = countLeadingZeros64(aSig);
*zSigPtr = aSig<<shiftCount;
*zExpPtr = 1 - shiftCount;
}
