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Move helper functions for optimizing division by constant into the APInt 

class.

llvm-svn: 70488
This commit is contained in:
Jay Foad 2009-04-30 10:15:35 +00:00
parent 902fddd1cf
commit fe0c648fee
3 changed files with 119 additions and 101 deletions
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25
llvm/include/llvm/ADT/APInt.h
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@ -1257,6 +1257,18 @@ public:
/// @returns the multiplicative inverse for a given modulo.
APInt multiplicativeInverse(const APInt& modulo) const;
/// @}
/// @name Support for division by constant
/// @{
/// Calculate the magic number for signed division by a constant.
struct ms;
ms magic() const;
/// Calculate the magic number for unsigned division by a constant.
struct mu;
mu magicu() const;
/// @}
/// @name Building-block Operations for APInt and APFloat
/// @{
@ -1388,6 +1400,19 @@ public:
/// @}
};
/// Magic data for optimising signed division by a constant.
struct APInt::ms {
APInt m; ///< magic number
unsigned s; ///< shift amount
};
/// Magic data for optimising unsigned division by a constant.
struct APInt::mu {
APInt m; ///< magic number
bool a; ///< add indicator
unsigned s; ///< shift amount
};
inline bool operator==(uint64_t V1, const APInt& V2) {
return V2 == V1;
}

103
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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@ -2434,105 +2434,6 @@ bool TargetLowering::isLegalAddressingMode(const AddrMode &AM,
return true;
}
struct mu {
APInt m; // magic number
bool a; // add indicator
unsigned s; // shift amount
};
/// magicu - calculate the magic numbers required to codegen an integer udiv as
/// a sequence of multiply, add and shifts. Requires that the divisor not be 0.
static mu magicu(const APInt& d) {
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 signedMin = APInt::getSignedMinValue(d.getBitWidth());
APInt signedMax = APInt::getSignedMaxValue(d.getBitWidth());
nc = allOnes - (-d).urem(d);
p = d.getBitWidth() - 1; // initialize p
q1 = signedMin.udiv(nc); // initialize q1 = 2p/nc
r1 = signedMin - q1*nc; // initialize r1 = rem(2p,nc)
q2 = signedMax.udiv(d); // initialize q2 = (2p-1)/d
r2 = signedMax - q2*d; // initialize r2 = rem((2p-1),d)
do {
p = p + 1;
if (r1.uge(nc - r1)) {
q1 = q1 + q1 + 1; // update q1
r1 = r1 + r1 - nc; // update r1
}
else {
q1 = q1+q1; // update q1
r1 = r1+r1; // update r1
}
if ((r2 + 1).uge(d - r2)) {
if (q2.uge(signedMax)) magu.a = 1;
q2 = q2+q2 + 1; // update q2
r2 = r2+r2 + 1 - d; // update r2
}
else {
if (q2.uge(signedMin)) magu.a = 1;
q2 = q2+q2; // update q2
r2 = r2+r2 + 1; // update r2
}
delta = d - 1 - r2;
} while (p < d.getBitWidth()*2 &&
(q1.ult(delta) || (q1 == delta && r1 == 0)));
magu.m = q2 + 1; // resulting magic number
magu.s = p - d.getBitWidth(); // resulting shift
return magu;
}
// Magic for divide replacement
struct ms {
APInt m; // magic number
unsigned s; // shift amount
};
/// magic - calculate the magic numbers required to codegen an integer sdiv as
/// a sequence of multiply and shifts. Requires that the divisor not be 0, 1,
/// or -1.
static ms magic(const APInt& d) {
unsigned p;
APInt ad, anc, delta, q1, r1, q2, r2, t;
APInt allOnes = APInt::getAllOnesValue(d.getBitWidth());
APInt signedMin = APInt::getSignedMinValue(d.getBitWidth());
APInt signedMax = APInt::getSignedMaxValue(d.getBitWidth());
struct ms mag;
ad = d.abs();
t = signedMin + (d.lshr(d.getBitWidth() - 1));
anc = t - 1 - t.urem(ad); // absolute value of nc
p = d.getBitWidth() - 1; // initialize p
q1 = signedMin.udiv(anc); // initialize q1 = 2p/abs(nc)
r1 = signedMin - q1*anc; // initialize r1 = rem(2p,abs(nc))
q2 = signedMin.udiv(ad); // initialize q2 = 2p/abs(d)
r2 = signedMin - q2*ad; // initialize r2 = rem(2p,abs(d))
do {
p = p + 1;
q1 = q1<<1; // update q1 = 2p/abs(nc)
r1 = r1<<1; // update r1 = rem(2p/abs(nc))
if (r1.uge(anc)) { // must be unsigned comparison
q1 = q1 + 1;
r1 = r1 - anc;
}
q2 = q2<<1; // update q2 = 2p/abs(d)
r2 = r2<<1; // update r2 = rem(2p/abs(d))
if (r2.uge(ad)) { // must be unsigned comparison
q2 = q2 + 1;
r2 = r2 - ad;
}
delta = ad - r2;
} while (q1.ule(delta) || (q1 == delta && r1 == 0));
mag.m = q2 + 1;
if (d.isNegative()) mag.m = -mag.m; // resulting magic number
mag.s = p - d.getBitWidth(); // resulting shift
return mag;
}
/// BuildSDIVSequence - Given an ISD::SDIV node expressing a divide by constant,
/// return a DAG expression to select that will generate the same value by
/// multiplying by a magic number. See:
@ -2548,7 +2449,7 @@ SDValue TargetLowering::BuildSDIV(SDNode *N, SelectionDAG &DAG,
return SDValue();
APInt d = cast<ConstantSDNode>(N->getOperand(1))->getAPIntValue();
ms magics = magic(d);
APInt::ms magics = d.magic();
// Multiply the numerator (operand 0) by the magic value
// FIXME: We should support doing a MUL in a wider type
@ -2607,7 +2508,7 @@ SDValue TargetLowering::BuildUDIV(SDNode *N, SelectionDAG &DAG,
// FIXME: We should use a narrower constant when the upper
// bits are known to be zero.
ConstantSDNode *N1C = cast<ConstantSDNode>(N->getOperand(1));
mu magics = magicu(N1C->getAPIntValue());
APInt::mu magics = N1C->getAPIntValue().magicu();
// Multiply the numerator (operand 0) by the magic value
// FIXME: We should support doing a MUL in a wider type

92
llvm/lib/Support/APInt.cpp
View File

@ -1435,6 +1435,98 @@ APInt APInt::multiplicativeInverse(const APInt& modulo) const {
return t[i].isNegative() ? t[i] + modulo : t[i];
}
/// Calculate the magic numbers required to implement a signed integer division
/// by a constant as a sequence of multiplies, adds and shifts. Requires that
/// the divisor not be 0, 1, or -1. Taken from "Hacker's Delight", Henry S.
/// Warren, Jr., chapter 10.
APInt::ms APInt::magic() const {
const APInt& d = *this;
unsigned p;
APInt ad, anc, delta, q1, r1, q2, r2, t;
APInt allOnes = APInt::getAllOnesValue(d.getBitWidth());
APInt signedMin = APInt::getSignedMinValue(d.getBitWidth());
APInt signedMax = APInt::getSignedMaxValue(d.getBitWidth());
struct ms mag;
ad = d.abs();
t = signedMin + (d.lshr(d.getBitWidth() - 1));
anc = t - 1 - t.urem(ad); // absolute value of nc
p = d.getBitWidth() - 1; // initialize p
q1 = signedMin.udiv(anc); // initialize q1 = 2p/abs(nc)
r1 = signedMin - q1*anc; // initialize r1 = rem(2p,abs(nc))
q2 = signedMin.udiv(ad); // initialize q2 = 2p/abs(d)
r2 = signedMin - q2*ad; // initialize r2 = rem(2p,abs(d))
do {
p = p + 1;
q1 = q1<<1; // update q1 = 2p/abs(nc)
r1 = r1<<1; // update r1 = rem(2p/abs(nc))
if (r1.uge(anc)) { // must be unsigned comparison
q1 = q1 + 1;
r1 = r1 - anc;
}
q2 = q2<<1; // update q2 = 2p/abs(d)
r2 = r2<<1; // update r2 = rem(2p/abs(d))
if (r2.uge(ad)) { // must be unsigned comparison
q2 = q2 + 1;
r2 = r2 - ad;
}
delta = ad - r2;
} while (q1.ule(delta) || (q1 == delta && r1 == 0));
mag.m = q2 + 1;
if (d.isNegative()) mag.m = -mag.m; // resulting magic number
mag.s = p - d.getBitWidth(); // resulting shift
return mag;
}
/// Calculate the magic numbers required to implement an unsigned integer
/// 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 {
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 signedMin = APInt::getSignedMinValue(d.getBitWidth());
APInt signedMax = APInt::getSignedMaxValue(d.getBitWidth());
nc = allOnes - (-d).urem(d);
p = d.getBitWidth() - 1; // initialize p
q1 = signedMin.udiv(nc); // initialize q1 = 2p/nc
r1 = signedMin - q1*nc; // initialize r1 = rem(2p,nc)
q2 = signedMax.udiv(d); // initialize q2 = (2p-1)/d
r2 = signedMax - q2*d; // initialize r2 = rem((2p-1),d)
do {
p = p + 1;
if (r1.uge(nc - r1)) {
q1 = q1 + q1 + 1; // update q1
r1 = r1 + r1 - nc; // update r1
}
else {
q1 = q1+q1; // update q1
r1 = r1+r1; // update r1
}
if ((r2 + 1).uge(d - r2)) {
if (q2.uge(signedMax)) magu.a = 1;
q2 = q2+q2 + 1; // update q2
r2 = r2+r2 + 1 - d; // update r2
}
else {
if (q2.uge(signedMin)) magu.a = 1;
q2 = q2+q2; // update q2
r2 = r2+r2 + 1; // update r2
}
delta = d - 1 - r2;
} while (p < d.getBitWidth()*2 &&
(q1.ult(delta) || (q1 == delta && r1 == 0)));
magu.m = q2 + 1; // resulting magic number
magu.s = p - d.getBitWidth(); // resulting shift
return magu;
}
/// Implementation of Knuth's Algorithm D (Division of nonnegative integers)
/// from "Art of Computer Programming, Volume 2", section 4.3.1, p. 272. The
/// variables here have the same names as in the algorithm. Comments explain