blockfreq: Defer to BranchProbability::scale() (again)

Change `BlockFrequency` to defer to `BranchProbability::scale()` and
`BranchProbability::scaleByInverse()`.

This removes `BlockFrequency::scale()` from its API (and drops the
ability to see the remainder), but the only user was the unit tests.  If
some code in the future needs an API that exposes the remainder, we can
add something to `BranchProbability`, but I find that unlikely.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207550 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 93 deletions

diff --git a/lib/Support/BlockFrequency.cpp b/lib/Support/BlockFrequency.cpp
index 00cf75bd5c..6f7e341904 100644
--- a/lib/Support/BlockFrequency.cpp
+++ b/lib/Support/BlockFrequency.cpp
@@ -18,94 +18,8 @@
 
 using namespace llvm;
 
-/// Multiply FREQ by N and store result in W array.
-static void mult96bit(uint64_t freq, uint32_t N, uint32_t W[3]) {
-  uint64_t u0 = freq & UINT32_MAX;
-  uint64_t u1 = freq >> 32;
-
-  // Represent 96-bit value as W[2]:W[1]:W[0];
-  uint64_t t = u0 * N;
-  uint64_t k = t >> 32;
-  W[0] = t;
-  t = u1 * N + k;
-  W[1] = t;
-  W[2] = t >> 32;
-}
-
-/// Divide 96-bit value stored in W[2]:W[1]:W[0] by D. Since our word size is a
-/// 32 bit unsigned integer, we can use a short division algorithm.
-static uint64_t divrem96bit(uint32_t W[3], uint32_t D, uint32_t *Rout) {
-  // We assume that W[2] is non-zero since if W[2] is not then the user should
-  // just use hardware division.
-  assert(W[2] && "This routine assumes that W[2] is non-zero since if W[2] is "
-         "zero, the caller should just use 64/32 hardware.");
-  uint32_t Q[3] = { 0, 0, 0 };
-
-  // The generalized short division algorithm sets i to m + n - 1, where n is
-  // the number of words in the divisior and m is the number of words by which
-  // the divident exceeds the divisor (i.e. m + n == the length of the dividend
-  // in words). Due to our assumption that W[2] is non-zero, we know that the
-  // dividend is of length 3 implying since n is 1 that m = 2. Thus we set i to
-  // m + n - 1 = 2 + 1 - 1 = 2.
-  uint32_t R = 0;
-  for (int i = 2; i >= 0; --i) {
-    uint64_t PartialD = uint64_t(R) << 32 | W[i];
-    if (PartialD == 0) {
-      Q[i] = 0;
-      R = 0;
-    } else if (PartialD < D) {
-      Q[i] = 0;
-      R = uint32_t(PartialD);
-    } else if (PartialD == D) {
-      Q[i] = 1;
-      R = 0;
-    } else {
-      Q[i] = uint32_t(PartialD / D);
-      R = uint32_t(PartialD - (Q[i] * D));
-    }
-  }
-
-  // If Q[2] is non-zero, then we overflowed.
-  uint64_t Result;
-  if (Q[2]) {
-    Result = UINT64_MAX;
-    R = D;
-  } else {
-    // Form the final uint64_t result, avoiding endianness issues.
-    Result = uint64_t(Q[0]) | (uint64_t(Q[1]) << 32);
-  }
-
-  if (Rout)
-    *Rout = R;
-
-  return Result;
-}
-
-uint32_t BlockFrequency::scale(uint32_t N, uint32_t D) {
-  assert(D != 0 && "Division by zero");
-
-  // Calculate Frequency * N.
-  uint64_t MulLo = (Frequency & UINT32_MAX) * N;
-  uint64_t MulHi = (Frequency >> 32) * N;
-  uint64_t MulRes = (MulHi << 32) + MulLo;
-
-  // If the product fits in 64 bits, just use built-in division.
-  if (MulHi <= UINT32_MAX && MulRes >= MulLo) {
-    Frequency = MulRes / D;
-    return MulRes % D;
-  }
-
-  // Product overflowed, use 96-bit operations.
-  // 96-bit value represented as W[2]:W[1]:W[0].
-  uint32_t W[3];
-  uint32_t R;
-  mult96bit(Frequency, N, W);
-  Frequency = divrem96bit(W, D, &R);
-  return R;
-}
-
 BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
-  scale(Prob.getNumerator(), Prob.getDenominator());
+  Frequency = Prob.scale(Frequency);
   return *this;
 }
 
@@ -117,7 +31,7 @@ BlockFrequency::operator*(const BranchProbability &Prob) const {
 }
 
 BlockFrequency &BlockFrequency::operator/=(const BranchProbability &Prob) {
-  scale(Prob.getDenominator(), Prob.getNumerator());
+  Frequency = Prob.scaleByInverse(Frequency);
   return *this;
 }
 
@@ -156,8 +70,3 @@ BlockFrequency &BlockFrequency::operator>>=(const unsigned count) {
   Frequency |= Frequency == 0;
   return *this;
 }
-
-uint32_t BlockFrequency::scale(const BranchProbability &Prob) {
-  return scale(Prob.getNumerator(), Prob.getDenominator());
-}
-