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[block-freq] Add the method APInt::nearestLogBase2().

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197272 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Gottesman 2013-12-13 20:47:37 +00:00
parent 5bb504f4ea
commit 46f829ee25
2 changed files with 53 additions and 4 deletions
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13
include/llvm/ADT/APInt.h
View File

@ -1507,6 +1507,19 @@ public:
return BitWidth - (*this - 1).countLeadingZeros();
}
/// \returns the nearest log base 2 of this APInt. Ties round up.
unsigned nearestLogBase2() const {
// This is implemented by taking the normal log 2 of a number and adding 1
// to it if MSB - 1 is set.
// We follow the model from logBase2 that logBase2(0) == UINT32_MAX. This
// works since if we have 0, MSB will be 0. Then we subtract one yielding
// UINT32_MAX. Finally extractBit of MSB - 1 will be UINT32_MAX implying
// that we get BitWidth - 1.
unsigned lg = logBase2();
return lg + unsigned(extractBit(std::min(lg - 1, BitWidth - 1)));
}
/// \returns the log base 2 of this APInt if its an exact power of two, -1
/// otherwise
int32_t exactLogBase2() const {

44
unittests/ADT/APIntTest.cpp
View File

@ -609,10 +609,10 @@ TEST(APIntTest, extractBit) {
// Multiword check.
integerPart E2[4] = {
0xeb6eb136591cba21ULL,
0x7b9358bd6a33f10aULL,
0x7e7ffa5eadd8846ULL,
0x305f341ca00b613dULL
0xEB6EB136591CBA21ULL,
0x7B9358BD6A33F10AULL,
0x7E7FFA5EADD8846ULL,
0x305F341CA00B613DULL
};
APInt A2(integerPartWidth*4, ArrayRef<integerPart>(E2, 4));
for (unsigned i = 0; i < 4; ++i) {
@ -623,4 +623,40 @@ TEST(APIntTest, extractBit) {
}
}
TEST(APIntTest, nearestLogBase2) {
// Single word check.
// Test round up.
uint64_t I1 = 0x1800001;
APInt A1(64, I1);
EXPECT_EQ(A1.nearestLogBase2(), A1.ceilLogBase2());
// Test round down.
uint64_t I2 = 0x1000011;
APInt A2(64, I2);
EXPECT_EQ(A2.nearestLogBase2(), A2.logBase2());
// Test ties round up.
uint64_t I3 = 0x1800000;
APInt A3(64, I3);
EXPECT_EQ(A3.nearestLogBase2(), A3.ceilLogBase2());
// Multiple word check.
// Test round up.
integerPart I4[4] = {0x0, 0xF, 0x18, 0x0};
APInt A4(integerPartWidth*4, ArrayRef<integerPart>(I4, 4));
EXPECT_EQ(A4.nearestLogBase2(), A4.ceilLogBase2());
// Test round down.
integerPart I5[4] = {0x0, 0xF, 0x10, 0x0};
APInt A5(integerPartWidth*4, ArrayRef<integerPart>(I5, 4));
EXPECT_EQ(A5.nearestLogBase2(), A5.logBase2());
// Test ties round up.
uint64_t I6[4] = {0x0, 0x0, 0x0, 0x18};
APInt A6(integerPartWidth*4, ArrayRef<integerPart>(I6, 4));
EXPECT_EQ(A6.nearestLogBase2(), A6.ceilLogBase2());
}
}