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Support: Extract ScaledNumbers::matchScale()

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llvm-svn: 211531
This commit is contained in:
Duncan P. N. Exon Smith 2014-06-23 20:40:45 +00:00
parent 95dc79eeda
commit dd8e45c6d7
3 changed files with 119 additions and 46 deletions
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50
include/llvm/Analysis/BlockFrequencyInfoImpl.h
View File

@ -247,14 +247,10 @@ private:
///
/// The value that compares smaller will lose precision, and possibly become
/// \a isZero().
UnsignedFloat matchExponents(UnsignedFloat X);
/// \brief Increase exponent to match another float.
///
/// Increases \c this to have an exponent matching \c X. May decrease the
/// exponent of \c X in the process, and \c this may possibly become \a
/// isZero().
void increaseExponentToMatch(UnsignedFloat &X, int32_t ExponentDiff);
UnsignedFloat matchExponents(UnsignedFloat X) {
ScaledNumbers::matchScales(Digits, Exponent, X.Digits, X.Exponent);
return X;
}
public:
/// \brief Scale a large number accurately.
@ -403,44 +399,6 @@ IntT UnsignedFloat<DigitsT>::toInt() const {
return N;
}
template <class DigitsT>
UnsignedFloat<DigitsT> UnsignedFloat<DigitsT>::matchExponents(UnsignedFloat X) {
if (isZero() || X.isZero() || Exponent == X.Exponent)
return X;
int32_t Diff = int32_t(X.Exponent) - int32_t(Exponent);
if (Diff > 0)
increaseExponentToMatch(X, Diff);
else
X.increaseExponentToMatch(*this, -Diff);
return X;
}
template <class DigitsT>
void UnsignedFloat<DigitsT>::increaseExponentToMatch(UnsignedFloat &X,
int32_t ExponentDiff) {
assert(ExponentDiff > 0);
if (ExponentDiff >= 2 * Width) {
*this = getZero();
return;
}
// Use up any leading zeros on X, and then shift this.
int32_t ShiftX = std::min(countLeadingZerosWidth(X.Digits), ExponentDiff);
assert(ShiftX < Width);
int32_t ShiftThis = ExponentDiff - ShiftX;
if (ShiftThis >= Width) {
*this = getZero();
return;
}
X.Digits <<= ShiftX;
X.Exponent -= ShiftX;
Digits >>= ShiftThis;
Exponent += ShiftThis;
return;
}
template <class DigitsT>
UnsignedFloat<DigitsT> &UnsignedFloat<DigitsT>::
operator+=(const UnsignedFloat &X) {

51
include/llvm/Support/ScaledNumber.h
View File

@ -24,6 +24,7 @@
#include "llvm/Support/MathExtras.h"
#include <algorithm>
#include <cstdint>
#include <limits>
#include <utility>
@ -263,6 +264,56 @@ int compare(DigitsT LDigits, int16_t LScale, DigitsT RDigits, int16_t RScale) {
return -compareImpl(RDigits, LDigits, LScale - RScale);
}
/// \brief Match scales of two numbers.
///
/// Given two scaled numbers, match up their scales. Change the digits and
/// scales in place. Shift the digits as necessary to form equivalent numbers,
/// losing precision only when necessary.
///
/// If the output value of \c LDigits (\c RDigits) is \c 0, the output value of
/// \c LScale (\c RScale) is unspecified. If both \c LDigits and \c RDigits
/// are \c 0, the output value is one of \c LScale and \c RScale; which is
/// unspecified.
template <class DigitsT>
void matchScales(DigitsT &LDigits, int16_t &LScale, DigitsT &RDigits,
int16_t &RScale) {
static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned");
if (LScale < RScale) {
// Swap arguments.
matchScales(RDigits, RScale, LDigits, LScale);
return;
}
if (!LDigits || !RDigits || LScale == RScale)
return;
// Now LScale > RScale. Get the difference.
int32_t ScaleDiff = int32_t(LScale) - RScale;
if (ScaleDiff >= 2 * getWidth<DigitsT>()) {
// Don't bother shifting. RDigits will get zero-ed out anyway.
RDigits = 0;
return;
}
// Shift LDigits left as much as possible, then shift RDigits right.
int32_t ShiftL = std::min<int32_t>(countLeadingZeros(LDigits), ScaleDiff);
assert(ShiftL < getWidth<DigitsT>() && "can't shift more than width");
int32_t ShiftR = ScaleDiff - ShiftL;
if (ShiftR >= getWidth<DigitsT>()) {
// Don't bother shifting. RDigits will get zero-ed out anyway.
RDigits = 0;
return;
}
LDigits <<= ShiftL;
RDigits >>= ShiftR;
LScale -= ShiftL;
RScale += ShiftR;
assert(LScale == RScale && "scales should match");
}
} // end namespace ScaledNumbers
} // end namespace llvm

64
unittests/Support/ScaledNumberTest.cpp
View File

@ -322,4 +322,68 @@ TEST(ScaledNumberHelpersTest, compare) {
EXPECT_EQ(-1, compare(UINT64_MAX, 0, UINT64_C(1), 64));
}
TEST(ScaledNumberHelpersTest, matchScales) {
typedef std::tuple<uint32_t, int16_t, uint32_t, int16_t> Pair32;
typedef std::tuple<uint64_t, int16_t, uint64_t, int16_t> Pair64;
#define MATCH_SCALES(T, LDIn, LSIn, RDIn, RSIn, LDOut, RDOut, SOut) \
do { \
T LDx = LDIn; \
T RDx = RDIn; \
T LDy = LDOut; \
T RDy = RDOut; \
int16_t LSx = LSIn; \
int16_t RSx = RSIn; \
int16_t Sy = SOut; \
\
matchScales(LDx, LSx, RDx, RSx); \
EXPECT_EQ(LDy, LDx); \
EXPECT_EQ(RDy, RDx); \
if (LDy) \
EXPECT_EQ(Sy, LSx); \
if (RDy) \
EXPECT_EQ(Sy, RSx); \
} while (false)
MATCH_SCALES(uint32_t, 0, 0, 0, 0, 0, 0, 0);
MATCH_SCALES(uint32_t, 0, 50, 7, 1, 0, 7, 1);
MATCH_SCALES(uint32_t, UINT32_C(1) << 31, 1, 9, 0, UINT32_C(1) << 31, 4, 1);
MATCH_SCALES(uint32_t, UINT32_C(1) << 31, 2, 9, 0, UINT32_C(1) << 31, 2, 2);
MATCH_SCALES(uint32_t, UINT32_C(1) << 31, 3, 9, 0, UINT32_C(1) << 31, 1, 3);
MATCH_SCALES(uint32_t, UINT32_C(1) << 31, 4, 9, 0, UINT32_C(1) << 31, 0, 4);
MATCH_SCALES(uint32_t, UINT32_C(1) << 30, 4, 9, 0, UINT32_C(1) << 31, 1, 3);
MATCH_SCALES(uint32_t, UINT32_C(1) << 29, 4, 9, 0, UINT32_C(1) << 31, 2, 2);
MATCH_SCALES(uint32_t, UINT32_C(1) << 28, 4, 9, 0, UINT32_C(1) << 31, 4, 1);
MATCH_SCALES(uint32_t, UINT32_C(1) << 27, 4, 9, 0, UINT32_C(1) << 31, 9, 0);
MATCH_SCALES(uint32_t, 7, 1, 0, 50, 7, 0, 1);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 31, 1, 4, UINT32_C(1) << 31, 1);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 31, 2, 2, UINT32_C(1) << 31, 2);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 31, 3, 1, UINT32_C(1) << 31, 3);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 31, 4, 0, UINT32_C(1) << 31, 4);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 30, 4, 1, UINT32_C(1) << 31, 3);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 29, 4, 2, UINT32_C(1) << 31, 2);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 28, 4, 4, UINT32_C(1) << 31, 1);
MATCH_SCALES(uint32_t, 9, 0, UINT32_C(1) << 27, 4, 9, UINT32_C(1) << 31, 0);
MATCH_SCALES(uint64_t, 0, 0, 0, 0, 0, 0, 0);
MATCH_SCALES(uint64_t, 0, 100, 7, 1, 0, 7, 1);
MATCH_SCALES(uint64_t, UINT64_C(1) << 63, 1, 9, 0, UINT64_C(1) << 63, 4, 1);
MATCH_SCALES(uint64_t, UINT64_C(1) << 63, 2, 9, 0, UINT64_C(1) << 63, 2, 2);
MATCH_SCALES(uint64_t, UINT64_C(1) << 63, 3, 9, 0, UINT64_C(1) << 63, 1, 3);
MATCH_SCALES(uint64_t, UINT64_C(1) << 63, 4, 9, 0, UINT64_C(1) << 63, 0, 4);
MATCH_SCALES(uint64_t, UINT64_C(1) << 62, 4, 9, 0, UINT64_C(1) << 63, 1, 3);
MATCH_SCALES(uint64_t, UINT64_C(1) << 61, 4, 9, 0, UINT64_C(1) << 63, 2, 2);
MATCH_SCALES(uint64_t, UINT64_C(1) << 60, 4, 9, 0, UINT64_C(1) << 63, 4, 1);
MATCH_SCALES(uint64_t, UINT64_C(1) << 59, 4, 9, 0, UINT64_C(1) << 63, 9, 0);
MATCH_SCALES(uint64_t, 7, 1, 0, 100, 7, 0, 1);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 63, 1, 4, UINT64_C(1) << 63, 1);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 63, 2, 2, UINT64_C(1) << 63, 2);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 63, 3, 1, UINT64_C(1) << 63, 3);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 63, 4, 0, UINT64_C(1) << 63, 4);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 62, 4, 1, UINT64_C(1) << 63, 3);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 61, 4, 2, UINT64_C(1) << 63, 2);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 60, 4, 4, UINT64_C(1) << 63, 1);
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 59, 4, 9, UINT64_C(1) << 63, 0);
}
} // end namespace