[llvm-commits] [llvm] r127828 - in /llvm/trunk: include/llvm/ADT/APInt.h lib/Support/APInt.cpp unittests/ADT/APIntTest.cpp

[Benjamin Kramer]

Author: d0k
Date: Thu Mar 17 15:39:06 2011
New Revision: 127828

URL: http://llvm.org/viewvc/llvm-project?rev=127828&view=rev
Log:
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.

Modified:
    llvm/trunk/include/llvm/ADT/APInt.h
    llvm/trunk/lib/Support/APInt.cpp
    llvm/trunk/unittests/ADT/APIntTest.cpp

Modified: llvm/trunk/include/llvm/ADT/APInt.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/APInt.h?rev=127828&r1=127827&r2=127828&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/APInt.h (original)
+++ llvm/trunk/include/llvm/ADT/APInt.h Thu Mar 17 15:39:06 2011
@@ -1372,7 +1372,7 @@
 
   /// 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

Modified: llvm/trunk/lib/Support/APInt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APInt.cpp?rev=127828&r1=127827&r2=127828&view=diff
==============================================================================
--- llvm/trunk/lib/Support/APInt.cpp (original)
+++ llvm/trunk/lib/Support/APInt.cpp Thu Mar 17 15:39:06 2011
@@ -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());
 

Modified: llvm/trunk/unittests/ADT/APIntTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/APIntTest.cpp?rev=127828&r1=127827&r2=127828&view=diff
==============================================================================
--- llvm/trunk/unittests/ADT/APIntTest.cpp (original)
+++ llvm/trunk/unittests/ADT/APIntTest.cpp Thu Mar 17 15:39:06 2011
@@ -348,6 +348,8 @@
   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