Index: lib/Support/APInt.cpp
===================================================================
--- lib/Support/APInt.cpp
+++ lib/Support/APInt.cpp
@@ -1252,12 +1252,18 @@
   // b denotes the base of the number system. In our case b is 2^32.
   const uint64_t b = uint64_t(1) << 32;
 
-  DEBUG(dbgs() << "KnuthDiv: m=" << m << " n=" << n << '\n');
-  DEBUG(dbgs() << "KnuthDiv: original:");
-  DEBUG(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
-  DEBUG(dbgs() << " by");
-  DEBUG(for (int i = n; i >0; i--) dbgs() << " " << v[i-1]);
-  DEBUG(dbgs() << '\n');
+#ifdef KNUTH_DEBUG
+#define DEBUG_KNUTH(X) DEBUG(X)
+#else
+#define DEBUG_KNUTH(X) do {} while(false)
+#endif
+
+  DEBUG_KNUTH(dbgs() << "KnuthDiv: m=" << m << " n=" << n << '\n');
+  DEBUG_KNUTH(dbgs() << "KnuthDiv: original:");
+  DEBUG_KNUTH(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
+  DEBUG_KNUTH(dbgs() << " by");
+  DEBUG_KNUTH(for (int i = n; i >0; i--) dbgs() << " " << v[i-1]);
+  DEBUG_KNUTH(dbgs() << '\n');
   // D1. [Normalize.] Set d = b / (v[n-1] + 1) and multiply all the digits of
   // u and v by d. Note that we have taken Knuth's advice here to use a power
   // of 2 value for d such that d * v[n-1] >= b/2 (b is the base). A power of
@@ -1283,16 +1289,16 @@
   }
   u[m+n] = u_carry;
 
-  DEBUG(dbgs() << "KnuthDiv:   normal:");
-  DEBUG(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
-  DEBUG(dbgs() << " by");
-  DEBUG(for (int i = n; i >0; i--) dbgs() << " " << v[i-1]);
-  DEBUG(dbgs() << '\n');
+  DEBUG_KNUTH(dbgs() << "KnuthDiv:   normal:");
+  DEBUG_KNUTH(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
+  DEBUG_KNUTH(dbgs() << " by");
+  DEBUG_KNUTH(for (int i = n; i >0; i--) dbgs() << " " << v[i-1]);
+  DEBUG_KNUTH(dbgs() << '\n');
 
   // D2. [Initialize j.]  Set j to m. This is the loop counter over the places.
   int j = m;
   do {
-    DEBUG(dbgs() << "KnuthDiv: quotient digit #" << j << '\n');
+    DEBUG_KNUTH(dbgs() << "KnuthDiv: quotient digit #" << j << '\n');
     // D3. [Calculate q'.].
     //     Set qp = (u[j+n]*b + u[j+n-1]) / v[n-1]. (qp=qprime=q')
     //     Set rp = (u[j+n]*b + u[j+n-1]) % v[n-1]. (rp=rprime=r')
@@ -1302,7 +1308,7 @@
     // value qp is one too large, and it eliminates all cases where qp is two
     // too large.
     uint64_t dividend = Make_64(u[j+n], u[j+n-1]);
-    DEBUG(dbgs() << "KnuthDiv: dividend == " << dividend << '\n');
+    DEBUG_KNUTH(dbgs() << "KnuthDiv: dividend == " << dividend << '\n');
     uint64_t qp = dividend / v[n-1];
     uint64_t rp = dividend % v[n-1];
     if (qp == b || qp*v[n-2] > b*rp + u[j+n-2]) {
@@ -1311,7 +1317,7 @@
       if (rp < b && (qp == b || qp*v[n-2] > b*rp + u[j+n-2]))
         qp--;
     }
-    DEBUG(dbgs() << "KnuthDiv: qp == " << qp << ", rp == " << rp << '\n');
+    DEBUG_KNUTH(dbgs() << "KnuthDiv: qp == " << qp << ", rp == " << rp << '\n');
 
     // D4. [Multiply and subtract.] Replace (u[j+n]u[j+n-1]...u[j]) with
     // (u[j+n]u[j+n-1]..u[j]) - qp * (v[n-1]...v[1]v[0]). This computation
@@ -1327,15 +1333,15 @@
       int64_t subres = int64_t(u[j+i]) - borrow - Lo_32(p);
       u[j+i] = Lo_32(subres);
       borrow = Hi_32(p) - Hi_32(subres);
-      DEBUG(dbgs() << "KnuthDiv: u[j+i] = " << u[j+i]
+      DEBUG_KNUTH(dbgs() << "KnuthDiv: u[j+i] = " << u[j+i]
                    << ", borrow = " << borrow << '\n');
     }
     bool isNeg = u[j+n] < borrow;
     u[j+n] -= Lo_32(borrow);
 
-    DEBUG(dbgs() << "KnuthDiv: after subtraction:");
-    DEBUG(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
-    DEBUG(dbgs() << '\n');
+    DEBUG_KNUTH(dbgs() << "KnuthDiv: after subtraction:");
+    DEBUG_KNUTH(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
+    DEBUG_KNUTH(dbgs() << '\n');
 
     // D5. [Test remainder.] Set q[j] = qp. If the result of step D4 was
     // negative, go to step D6; otherwise go on to step D7.
@@ -1356,16 +1362,16 @@
       }
       u[j+n] += carry;
     }
-    DEBUG(dbgs() << "KnuthDiv: after correction:");
-    DEBUG(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
-    DEBUG(dbgs() << "\nKnuthDiv: digit result = " << q[j] << '\n');
+    DEBUG_KNUTH(dbgs() << "KnuthDiv: after correction:");
+    DEBUG_KNUTH(for (int i = m+n; i >=0; i--) dbgs() << " " << u[i]);
+    DEBUG_KNUTH(dbgs() << "\nKnuthDiv: digit result = " << q[j] << '\n');
 
   // D7. [Loop on j.]  Decrease j by one. Now if j >= 0, go back to D3.
   } while (--j >= 0);
 
-  DEBUG(dbgs() << "KnuthDiv: quotient:");
-  DEBUG(for (int i = m; i >=0; i--) dbgs() <<" " << q[i]);
-  DEBUG(dbgs() << '\n');
+  DEBUG_KNUTH(dbgs() << "KnuthDiv: quotient:");
+  DEBUG_KNUTH(for (int i = m; i >=0; i--) dbgs() <<" " << q[i]);
+  DEBUG_KNUTH(dbgs() << '\n');
 
   // D8. [Unnormalize]. Now q[...] is the desired quotient, and the desired
   // remainder may be obtained by dividing u[...] by d. If r is non-null we
@@ -1376,21 +1382,23 @@
     // shift right here.
     if (shift) {
       uint32_t carry = 0;
-      DEBUG(dbgs() << "KnuthDiv: remainder:");
+      DEBUG_KNUTH(dbgs() << "KnuthDiv: remainder:");
       for (int i = n-1; i >= 0; i--) {
         r[i] = (u[i] >> shift) | carry;
         carry = u[i] << (32 - shift);
-        DEBUG(dbgs() << " " << r[i]);
+        DEBUG_KNUTH(dbgs() << " " << r[i]);
       }
     } else {
       for (int i = n-1; i >= 0; i--) {
         r[i] = u[i];
-        DEBUG(dbgs() << " " << r[i]);
+        DEBUG_KNUTH(dbgs() << " " << r[i]);
       }
     }
-    DEBUG(dbgs() << '\n');
+    DEBUG_KNUTH(dbgs() << '\n');
   }
-  DEBUG(dbgs() << '\n');
+  DEBUG_KNUTH(dbgs() << '\n');
+
+#undef DEBUG_KNUTH
 }
 
 void APInt::divide(const WordType *LHS, unsigned lhsWords, const WordType *RHS,