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Add a ceilLogBase2 function to APInt. 

llvm-svn: 83932
This commit is contained in:
Dan Gohman 2009-10-13 01:49:02 +00:00
parent 70e8505eb1
commit c4e367b854
2 changed files with 16 additions and 0 deletions
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5
llvm/include/llvm/ADT/APInt.h
View File

@ -1234,6 +1234,11 @@ public:
return BitWidth - 1 - countLeadingZeros();
}
/// @returns the ceil log base 2 of this APInt.
unsigned ceilLogBase2() const {
return BitWidth - (*this - 1).countLeadingZeros();
}
/// @returns the log base 2 of this APInt if its an exact power of two, -1
/// otherwise
int32_t exactLogBase2() const {

11
llvm/unittests/ADT/APIntTest.cpp
View File

@ -315,6 +315,17 @@ TEST(APIntTest, StringBitsNeeded16) {
EXPECT_EQ(9U, APInt::getBitsNeeded("-20", 16));
}
TEST(APIntTest, Log2) {
EXPECT_EQ(APInt(15, 7).logBase2(), 2);
EXPECT_EQ(APInt(15, 7).ceilLogBase2(), 3);
EXPECT_EQ(APInt(15, 7).exactLogBase2(), -1);
EXPECT_EQ(APInt(15, 8).logBase2(), 3);
EXPECT_EQ(APInt(15, 8).ceilLogBase2(), 3);
EXPECT_EQ(APInt(15, 8).exactLogBase2(), 3);
EXPECT_EQ(APInt(15, 9).logBase2(), 3);
EXPECT_EQ(APInt(15, 9).ceilLogBase2(), 4);
EXPECT_EQ(APInt(15, 9).exactLogBase2(), -1);
}
#ifdef GTEST_HAS_DEATH_TEST
TEST(APIntTest, StringDeath) {