Add an argument to APInt's magic udiv calculation to specify the number of bits that are known zero in the divided number.
This will come in handy soon.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127828 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index 08f36d2..f4aae72 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -1517,13 +1517,15 @@
/// 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());