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Add an argument to APInt's magic udiv calculation to specify the number of bits that are known zero in the divided number.

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This will come in handy soon.

llvm-svn: 127828
This commit is contained in:
Benjamin Kramer 2011-03-17 20:39:06 +00:00
parent 047a25b0b0
commit a85996c235
3 changed files with 7 additions and 3 deletions
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2
include/llvm/ADT/APInt.h
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@ -1372,7 +1372,7 @@ public:
/// Calculate the magic number for unsigned division by a constant.
struct mu;
mu magicu() const;
mu magicu(unsigned LeadingZeros = 0) const;
/// @}
/// @name Building-block Operations for APInt and APFloat

6
lib/Support/APInt.cpp
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@ -1517,13 +1517,15 @@ APInt::ms APInt::magic() const {
/// division by a constant as a sequence of multiplies, adds and shifts.
/// Requires that the divisor not be 0. Taken from "Hacker's Delight", Henry
/// S. Warren, Jr., chapter 10.
APInt::mu APInt::magicu() const {
/// LeadingZeros can be used to simplify the calculation if the upper bits
/// of the devided value are known zero.
APInt::mu APInt::magicu(unsigned LeadingZeros) const {
const APInt& d = *this;
unsigned p;
APInt nc, delta, q1, r1, q2, r2;
struct mu magu;
magu.a = 0; // initialize "add" indicator
APInt allOnes = APInt::getAllOnesValue(d.getBitWidth());
APInt allOnes = APInt::getAllOnesValue(d.getBitWidth()).lshr(LeadingZeros);
APInt signedMin = APInt::getSignedMinValue(d.getBitWidth());
APInt signedMax = APInt::getSignedMaxValue(d.getBitWidth());

2
unittests/ADT/APIntTest.cpp
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@ -348,6 +348,8 @@ TEST(APIntTest, magicu) {
EXPECT_EQ(APInt(32, 5).magicu().s, 2U);
EXPECT_EQ(APInt(32, 7).magicu().m, APInt(32, "24924925", 16));
EXPECT_EQ(APInt(32, 7).magicu().s, 3U);
EXPECT_EQ(APInt(64, 25).magicu(1).m, APInt(64, "A3D70A3D70A3D70B", 16));
EXPECT_EQ(APInt(64, 25).magicu(1).s, 4U);
}
#ifdef GTEST_HAS_DEATH_TEST