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Move the target constant divide optimization up into the dag combiner, so

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that the nodes can be folded with other nodes, and we can not duplicate
code in every backend.  Alpha will probably want this too.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23835 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman 2005-10-20 02:15:44 +00:00
parent d32d4a93f6
commit 6957523b9d
4 changed files with 265 additions and 314 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

263
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -180,6 +180,9 @@ namespace {
SDOperand N3, ISD::CondCode CC);
SDOperand SimplifySetCC(MVT::ValueType VT, SDOperand N0, SDOperand N1,
ISD::CondCode Cond, bool foldBooleans = true);
SDOperand BuildSDIV(SDNode *N);
SDOperand BuildUDIV(SDNode *N);
public:
DAGCombiner(SelectionDAG &D)
: DAG(D), TLI(D.getTargetLoweringInfo()), AfterLegalize(false) {}
@ -189,6 +192,178 @@ public:
};
}
struct ms {
int64_t m; // magic number
int64_t s; // shift amount
};
struct mu {
uint64_t m; // magic number
int64_t a; // add indicator
int64_t 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 magic32(int32_t d) {
int32_t p;
uint32_t ad, anc, delta, q1, r1, q2, r2, t;
const uint32_t two31 = 0x80000000U;
struct ms mag;
ad = abs(d);
t = two31 + ((uint32_t)d >> 31);
anc = t - 1 - t%ad; // absolute value of nc
p = 31; // initialize p
q1 = two31/anc; // initialize q1 = 2p/abs(nc)
r1 = two31 - q1*anc; // initialize r1 = rem(2p,abs(nc))
q2 = two31/ad; // initialize q2 = 2p/abs(d)
r2 = two31 - q2*ad; // initialize r2 = rem(2p,abs(d))
do {
p = p + 1;
q1 = 2*q1; // update q1 = 2p/abs(nc)
r1 = 2*r1; // update r1 = rem(2p/abs(nc))
if (r1 >= anc) { // must be unsigned comparison
q1 = q1 + 1;
r1 = r1 - anc;
}
q2 = 2*q2; // update q2 = 2p/abs(d)
r2 = 2*r2; // update r2 = rem(2p/abs(d))
if (r2 >= ad) { // must be unsigned comparison
q2 = q2 + 1;
r2 = r2 - ad;
}
delta = ad - r2;
} while (q1 < delta || (q1 == delta && r1 == 0));
mag.m = (int32_t)(q2 + 1); // make sure to sign extend
if (d < 0) mag.m = -mag.m; // resulting magic number
mag.s = p - 32; // resulting shift
return mag;
}
/// 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 magicu32(uint32_t d) {
int32_t p;
uint32_t nc, delta, q1, r1, q2, r2;
struct mu magu;
magu.a = 0; // initialize "add" indicator
nc = - 1 - (-d)%d;
p = 31; // initialize p
q1 = 0x80000000/nc; // initialize q1 = 2p/nc
r1 = 0x80000000 - q1*nc; // initialize r1 = rem(2p,nc)
q2 = 0x7FFFFFFF/d; // initialize q2 = (2p-1)/d
r2 = 0x7FFFFFFF - q2*d; // initialize r2 = rem((2p-1),d)
do {
p = p + 1;
if (r1 >= nc - r1 ) {
q1 = 2*q1 + 1; // update q1
r1 = 2*r1 - nc; // update r1
}
else {
q1 = 2*q1; // update q1
r1 = 2*r1; // update r1
}
if (r2 + 1 >= d - r2) {
if (q2 >= 0x7FFFFFFF) magu.a = 1;
q2 = 2*q2 + 1; // update q2
r2 = 2*r2 + 1 - d; // update r2
}
else {
if (q2 >= 0x80000000) magu.a = 1;
q2 = 2*q2; // update q2
r2 = 2*r2 + 1; // update r2
}
delta = d - 1 - r2;
} while (p < 64 && (q1 < delta || (q1 == delta && r1 == 0)));
magu.m = q2 + 1; // resulting magic number
magu.s = p - 32; // resulting shift
return magu;
}
/// 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 magic64(int64_t d) {
int64_t p;
uint64_t ad, anc, delta, q1, r1, q2, r2, t;
const uint64_t two63 = 9223372036854775808ULL; // 2^63
struct ms mag;
ad = llabs(d);
t = two63 + ((uint64_t)d >> 63);
anc = t - 1 - t%ad; // absolute value of nc
p = 63; // initialize p
q1 = two63/anc; // initialize q1 = 2p/abs(nc)
r1 = two63 - q1*anc; // initialize r1 = rem(2p,abs(nc))
q2 = two63/ad; // initialize q2 = 2p/abs(d)
r2 = two63 - q2*ad; // initialize r2 = rem(2p,abs(d))
do {
p = p + 1;
q1 = 2*q1; // update q1 = 2p/abs(nc)
r1 = 2*r1; // update r1 = rem(2p/abs(nc))
if (r1 >= anc) { // must be unsigned comparison
q1 = q1 + 1;
r1 = r1 - anc;
}
q2 = 2*q2; // update q2 = 2p/abs(d)
r2 = 2*r2; // update r2 = rem(2p/abs(d))
if (r2 >= ad) { // must be unsigned comparison
q2 = q2 + 1;
r2 = r2 - ad;
}
delta = ad - r2;
} while (q1 < delta || (q1 == delta && r1 == 0));
mag.m = q2 + 1;
if (d < 0) mag.m = -mag.m; // resulting magic number
mag.s = p - 64; // resulting shift
return mag;
}
/// 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 magicu64(uint64_t d)
{
int64_t p;
uint64_t nc, delta, q1, r1, q2, r2;
struct mu magu;
magu.a = 0; // initialize "add" indicator
nc = - 1 - (-d)%d;
p = 63; // initialize p
q1 = 0x8000000000000000ull/nc; // initialize q1 = 2p/nc
r1 = 0x8000000000000000ull - q1*nc; // initialize r1 = rem(2p,nc)
q2 = 0x7FFFFFFFFFFFFFFFull/d; // initialize q2 = (2p-1)/d
r2 = 0x7FFFFFFFFFFFFFFFull - q2*d; // initialize r2 = rem((2p-1),d)
do {
p = p + 1;
if (r1 >= nc - r1 ) {
q1 = 2*q1 + 1; // update q1
r1 = 2*r1 - nc; // update r1
}
else {
q1 = 2*q1; // update q1
r1 = 2*r1; // update r1
}
if (r2 + 1 >= d - r2) {
if (q2 >= 0x7FFFFFFFFFFFFFFFull) magu.a = 1;
q2 = 2*q2 + 1; // update q2
r2 = 2*r2 + 1 - d; // update r2
}
else {
if (q2 >= 0x8000000000000000ull) magu.a = 1;
q2 = 2*q2; // update q2
r2 = 2*r2 + 1; // update r2
}
delta = d - 1 - r2;
} while (p < 64 && (q1 < delta || (q1 == delta && r1 == 0)));
magu.m = q2 + 1; // resulting magic number
magu.s = p - 64; // resulting shift
return magu;
}
/// MaskedValueIsZero - Return true if 'Op & Mask' is known to be zero. We use
/// this predicate to simplify operations downstream. Op and Mask are known to
/// be the same type.
@ -608,12 +783,23 @@ SDOperand DAGCombiner::visitSDIV(SDNode *N) {
if (MaskedValueIsZero(N1, SignBit, TLI) &&
MaskedValueIsZero(N0, SignBit, TLI))
return DAG.getNode(ISD::UDIV, N1.getValueType(), N0, N1);
// if integer divide is expensive and we satisfy the requirements, emit an
// alternate sequence.
// FIXME: This currently opts out powers of two, since targets can often be
// more clever in those cases. In an idea world, we would have some way to
// detect that too.
if (N1C && !isPowerOf2_64(N1C->getSignExtended()) &&
(N1C->getSignExtended() < -1 || N1C->getSignExtended() > 1) &&
TLI.isOperationLegal(ISD::MULHS, VT) && TLI.isIntDivExpensive()) {
return BuildSDIV(N);
}
return SDOperand();
}
SDOperand DAGCombiner::visitUDIV(SDNode *N) {
SDOperand N0 = N->getOperand(0);
SDOperand N1 = N->getOperand(1);
MVT::ValueType VT = N->getValueType(0);
ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0.Val);
ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.Val);
@ -626,6 +812,10 @@ SDOperand DAGCombiner::visitUDIV(SDNode *N) {
return DAG.getNode(ISD::SRL, N->getValueType(0), N0,
DAG.getConstant(Log2_64(N1C->getValue()),
TLI.getShiftAmountTy()));
// fold (udiv x, c) -> alternate
if (N1C && N1C->getValue() && TLI.isOperationLegal(ISD::MULHU, VT) &&
TLI.isIntDivExpensive())
return BuildUDIV(N);
return SDOperand();
}
@ -2356,6 +2546,79 @@ SDOperand DAGCombiner::SimplifySetCC(MVT::ValueType VT, SDOperand N0,
return SDOperand();
}
/// 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:
/// <http://the.wall.riscom.net/books/proc/ppc/cwg/code2.html>
SDOperand DAGCombiner::BuildSDIV(SDNode *N) {
MVT::ValueType VT = N->getValueType(0);
assert((VT == MVT::i32 || VT == MVT::i64) &&
"BuildSDIV only operates on i32 or i64!");
int64_t d = cast<ConstantSDNode>(N->getOperand(1))->getValue();
ms magics = (VT == MVT::i32) ? magic32(d) : magic64(d);
// Multiply the numerator (operand 0) by the magic value
SDOperand Q = DAG.getNode(ISD::MULHS, VT, N->getOperand(0),
DAG.getConstant(magics.m, VT));
// If d > 0 and m < 0, add the numerator
if (d > 0 && magics.m < 0) {
Q = DAG.getNode(ISD::ADD, VT, Q, N->getOperand(0));
WorkList.push_back(Q.Val);
}
// If d < 0 and m > 0, subtract the numerator.
if (d < 0 && magics.m > 0) {
Q = DAG.getNode(ISD::SUB, VT, Q, N->getOperand(0));
WorkList.push_back(Q.Val);
}
// Shift right algebraic if shift value is nonzero
if (magics.s > 0) {
Q = DAG.getNode(ISD::SRA, VT, Q,
DAG.getConstant(magics.s, TLI.getShiftAmountTy()));
WorkList.push_back(Q.Val);
}
// Extract the sign bit and add it to the quotient
SDOperand T =
DAG.getNode(ISD::SRL, MVT::i32, Q,
DAG.getConstant(MVT::getSizeInBits(VT)-1,
TLI.getShiftAmountTy()));
WorkList.push_back(T.Val);
return DAG.getNode(ISD::ADD, VT, Q, T);
}
/// BuildUDIVSequence - Given an ISD::UDIV 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:
/// <http://the.wall.riscom.net/books/proc/ppc/cwg/code2.html>
SDOperand DAGCombiner::BuildUDIV(SDNode *N) {
MVT::ValueType VT = N->getValueType(0);
assert((VT == MVT::i32 || VT == MVT::i64) &&
"BuildUDIV only operates on i32 or i64!");
uint64_t d = cast<ConstantSDNode>(N->getOperand(1))->getValue();
mu magics = (VT == MVT::i32) ? magicu32(d) : magicu64(d);
// Multiply the numerator (operand 0) by the magic value
SDOperand Q = DAG.getNode(ISD::MULHU, VT, N->getOperand(0),
DAG.getConstant(magics.m, VT));
WorkList.push_back(Q.Val);
if (magics.a == 0) {
return DAG.getNode(ISD::SRL, VT, Q,
DAG.getConstant(magics.s, TLI.getShiftAmountTy()));
} else {
SDOperand NPQ = DAG.getNode(ISD::SUB, VT, N->getOperand(0), Q);
WorkList.push_back(NPQ.Val);
NPQ = DAG.getNode(ISD::SRL, VT, NPQ,
DAG.getConstant(1, TLI.getShiftAmountTy()));
WorkList.push_back(NPQ.Val);
NPQ = DAG.getNode(ISD::ADD, VT, NPQ, Q);
WorkList.push_back(NPQ.Val);
return DAG.getNode(ISD::SRL, VT, NPQ,
DAG.getConstant(magics.s-1, TLI.getShiftAmountTy()));
}
}
// SelectionDAG::Combine - This is the entry point for the file.
//
void SelectionDAG::Combine(bool RunningAfterLegalize) {

160
lib/Target/PowerPC/PPCISelDAGToDAG.cpp
View File

@ -513,149 +513,6 @@ static unsigned getCRIdxForSetCC(ISD::CondCode CC, bool& Inv) {
return 0;
}
// Structure used to return the necessary information to codegen an SDIV as
// a multiply.
struct ms {
int m; // magic number
int s; // shift amount
};
struct mu {
unsigned int m; // magic number
int a; // add indicator
int 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 struct ms magic(int d) {
int p;
unsigned int ad, anc, delta, q1, r1, q2, r2, t;
const unsigned int two31 = 0x80000000U;
struct ms mag;
ad = abs(d);
t = two31 + ((unsigned int)d >> 31);
anc = t - 1 - t%ad; // absolute value of nc
p = 31; // initialize p
q1 = two31/anc; // initialize q1 = 2p/abs(nc)
r1 = two31 - q1*anc; // initialize r1 = rem(2p,abs(nc))
q2 = two31/ad; // initialize q2 = 2p/abs(d)
r2 = two31 - q2*ad; // initialize r2 = rem(2p,abs(d))
do {
p = p + 1;
q1 = 2*q1; // update q1 = 2p/abs(nc)
r1 = 2*r1; // update r1 = rem(2p/abs(nc))
if (r1 >= anc) { // must be unsigned comparison
q1 = q1 + 1;
r1 = r1 - anc;
}
q2 = 2*q2; // update q2 = 2p/abs(d)
r2 = 2*r2; // update r2 = rem(2p/abs(d))
if (r2 >= ad) { // must be unsigned comparison
q2 = q2 + 1;
r2 = r2 - ad;
}
delta = ad - r2;
} while (q1 < delta || (q1 == delta && r1 == 0));
mag.m = q2 + 1;
if (d < 0) mag.m = -mag.m; // resulting magic number
mag.s = p - 32; // resulting shift
return mag;
}
/// 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 struct mu magicu(unsigned d)
{
int p;
unsigned int nc, delta, q1, r1, q2, r2;
struct mu magu;
magu.a = 0; // initialize "add" indicator
nc = - 1 - (-d)%d;
p = 31; // initialize p
q1 = 0x80000000/nc; // initialize q1 = 2p/nc
r1 = 0x80000000 - q1*nc; // initialize r1 = rem(2p,nc)
q2 = 0x7FFFFFFF/d; // initialize q2 = (2p-1)/d
r2 = 0x7FFFFFFF - q2*d; // initialize r2 = rem((2p-1),d)
do {
p = p + 1;
if (r1 >= nc - r1 ) {
q1 = 2*q1 + 1; // update q1
r1 = 2*r1 - nc; // update r1
}
else {
q1 = 2*q1; // update q1
r1 = 2*r1; // update r1
}
if (r2 + 1 >= d - r2) {
if (q2 >= 0x7FFFFFFF) magu.a = 1;
q2 = 2*q2 + 1; // update q2
r2 = 2*r2 + 1 - d; // update r2
}
else {
if (q2 >= 0x80000000) magu.a = 1;
q2 = 2*q2; // update q2
r2 = 2*r2 + 1; // update r2
}
delta = d - 1 - r2;
} while (p < 64 && (q1 < delta || (q1 == delta && r1 == 0)));
magu.m = q2 + 1; // resulting magic number
magu.s = p - 32; // resulting shift
return magu;
}
/// 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:
/// <http://the.wall.riscom.net/books/proc/ppc/cwg/code2.html>
SDOperand PPCDAGToDAGISel::BuildSDIVSequence(SDNode *N) {
int d = (int)cast<ConstantSDNode>(N->getOperand(1))->getValue();
ms magics = magic(d);
// Multiply the numerator (operand 0) by the magic value
SDOperand Q = CurDAG->getNode(ISD::MULHS, MVT::i32, N->getOperand(0),
CurDAG->getConstant(magics.m, MVT::i32));
// If d > 0 and m < 0, add the numerator
if (d > 0 && magics.m < 0)
Q = CurDAG->getNode(ISD::ADD, MVT::i32, Q, N->getOperand(0));
// If d < 0 and m > 0, subtract the numerator.
if (d < 0 && magics.m > 0)
Q = CurDAG->getNode(ISD::SUB, MVT::i32, Q, N->getOperand(0));
// Shift right algebraic if shift value is nonzero
if (magics.s > 0)
Q = CurDAG->getNode(ISD::SRA, MVT::i32, Q,
CurDAG->getConstant(magics.s, MVT::i32));
// Extract the sign bit and add it to the quotient
SDOperand T =
CurDAG->getNode(ISD::SRL, MVT::i32, Q, CurDAG->getConstant(31, MVT::i32));
return CurDAG->getNode(ISD::ADD, MVT::i32, Q, T);
}
/// BuildUDIVSequence - Given an ISD::UDIV 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:
/// <http://the.wall.riscom.net/books/proc/ppc/cwg/code2.html>
SDOperand PPCDAGToDAGISel::BuildUDIVSequence(SDNode *N) {
unsigned d = (unsigned)cast<ConstantSDNode>(N->getOperand(1))->getValue();
mu magics = magicu(d);
// Multiply the numerator (operand 0) by the magic value
SDOperand Q = CurDAG->getNode(ISD::MULHU, MVT::i32, N->getOperand(0),
CurDAG->getConstant(magics.m, MVT::i32));
if (magics.a == 0) {
return CurDAG->getNode(ISD::SRL, MVT::i32, Q,
CurDAG->getConstant(magics.s, MVT::i32));
} else {
SDOperand NPQ = CurDAG->getNode(ISD::SUB, MVT::i32, N->getOperand(0), Q);
NPQ = CurDAG->getNode(ISD::SRL, MVT::i32, NPQ,
CurDAG->getConstant(1, MVT::i32));
NPQ = CurDAG->getNode(ISD::ADD, MVT::i32, NPQ, Q);
return CurDAG->getNode(ISD::SRL, MVT::i32, NPQ,
CurDAG->getConstant(magics.s-1, MVT::i32));
}
}
SDOperand PPCDAGToDAGISel::SelectDYNAMIC_STACKALLOC(SDOperand Op) {
SDNode *N = Op.Val;
@ -1159,29 +1016,12 @@ SDOperand PPCDAGToDAGISel::Select(SDOperand Op) {
Op.getValue(1));
CurDAG->SelectNodeTo(N, PPC::NEG, MVT::i32, PT);
return SDOperand(N, 0);
} else if (Imm) {
SDOperand Result = Select(BuildSDIVSequence(N));
CodeGenMap[Op] = Result;
return Result;
}
}
// Other cases are autogenerated.
break;
}
case ISD::UDIV: {
// If this is a divide by constant, we can emit code using some magic
// constants to implement it as a multiply instead.
unsigned Imm;
if (isIntImmediate(N->getOperand(1), Imm) && Imm) {
SDOperand Result = Select(BuildUDIVSequence(N));
CodeGenMap[Op] = Result;
return Result;
}
// Other cases are autogenerated.
break;
}
case ISD::AND: {
unsigned Imm;
// If this is an and of a value rotated between 0 and 31 bits and then and'd

2
lib/Target/PowerPC/PPCISelLowering.cpp
View File

@ -27,6 +27,8 @@ PPCTargetLowering::PPCTargetLowering(TargetMachine &TM)
// Fold away setcc operations if possible.
setSetCCIsExpensive();
// Fold constant integer div/rem into an alternate sequence of instructions
setIntDivIsExpensive();
// Use _setjmp/_longjmp instead of setjmp/longjmp.
setUseUnderscoreSetJmpLongJmp(true);

154
lib/Target/PowerPC/PPCISelPattern.cpp
View File

@ -274,151 +274,6 @@ static unsigned IndexedOpForOp(unsigned Opcode) {
}
return 0;
}
// Structure used to return the necessary information to codegen an SDIV as
// a multiply.
struct ms {
int m; // magic number
int s; // shift amount
};
struct mu {
unsigned int m; // magic number
int a; // add indicator
int 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 struct ms magic(int d) {
int p;
unsigned int ad, anc, delta, q1, r1, q2, r2, t;
const unsigned int two31 = 0x80000000U;
struct ms mag;
ad = abs(d);
t = two31 + ((unsigned int)d >> 31);
anc = t - 1 - t%ad; // absolute value of nc
p = 31; // initialize p
q1 = two31/anc; // initialize q1 = 2p/abs(nc)
r1 = two31 - q1*anc; // initialize r1 = rem(2p,abs(nc))
q2 = two31/ad; // initialize q2 = 2p/abs(d)
r2 = two31 - q2*ad; // initialize r2 = rem(2p,abs(d))
do {
p = p + 1;
q1 = 2*q1; // update q1 = 2p/abs(nc)
r1 = 2*r1; // update r1 = rem(2p/abs(nc))
if (r1 >= anc) { // must be unsigned comparison
q1 = q1 + 1;
r1 = r1 - anc;
}
q2 = 2*q2; // update q2 = 2p/abs(d)
r2 = 2*r2; // update r2 = rem(2p/abs(d))
if (r2 >= ad) { // must be unsigned comparison
q2 = q2 + 1;
r2 = r2 - ad;
}
delta = ad - r2;
} while (q1 < delta || (q1 == delta && r1 == 0));
mag.m = q2 + 1;
if (d < 0) mag.m = -mag.m; // resulting magic number
mag.s = p - 32; // resulting shift
return mag;
}
/// 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 struct mu magicu(unsigned d)
{
int p;
unsigned int nc, delta, q1, r1, q2, r2;
struct mu magu;
magu.a = 0; // initialize "add" indicator
nc = - 1 - (-d)%d;
p = 31; // initialize p
q1 = 0x80000000/nc; // initialize q1 = 2p/nc
r1 = 0x80000000 - q1*nc; // initialize r1 = rem(2p,nc)
q2 = 0x7FFFFFFF/d; // initialize q2 = (2p-1)/d
r2 = 0x7FFFFFFF - q2*d; // initialize r2 = rem((2p-1),d)
do {
p = p + 1;
if (r1 >= nc - r1 ) {
q1 = 2*q1 + 1; // update q1
r1 = 2*r1 - nc; // update r1
}
else {
q1 = 2*q1; // update q1
r1 = 2*r1; // update r1
}
if (r2 + 1 >= d - r2) {
if (q2 >= 0x7FFFFFFF) magu.a = 1;
q2 = 2*q2 + 1; // update q2
r2 = 2*r2 + 1 - d; // update r2
}
else {
if (q2 >= 0x80000000) magu.a = 1;
q2 = 2*q2; // update q2
r2 = 2*r2 + 1; // update r2
}
delta = d - 1 - r2;
} while (p < 64 && (q1 < delta || (q1 == delta && r1 == 0)));
magu.m = q2 + 1; // resulting magic number
magu.s = p - 32; // resulting shift
return magu;
}
}
/// 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:
/// <http://the.wall.riscom.net/books/proc/ppc/cwg/code2.html>
SDOperand ISel::BuildSDIVSequence(SDOperand N) {
int d = (int)cast<ConstantSDNode>(N.getOperand(1))->getSignExtended();
ms magics = magic(d);
// Multiply the numerator (operand 0) by the magic value
SDOperand Q = ISelDAG->getNode(ISD::MULHS, MVT::i32, N.getOperand(0),
ISelDAG->getConstant(magics.m, MVT::i32));
// If d > 0 and m < 0, add the numerator
if (d > 0 && magics.m < 0)
Q = ISelDAG->getNode(ISD::ADD, MVT::i32, Q, N.getOperand(0));
// If d < 0 and m > 0, subtract the numerator.
if (d < 0 && magics.m > 0)
Q = ISelDAG->getNode(ISD::SUB, MVT::i32, Q, N.getOperand(0));
// Shift right algebraic if shift value is nonzero
if (magics.s > 0)
Q = ISelDAG->getNode(ISD::SRA, MVT::i32, Q,
ISelDAG->getConstant(magics.s, MVT::i32));
// Extract the sign bit and add it to the quotient
SDOperand T =
ISelDAG->getNode(ISD::SRL, MVT::i32, Q, ISelDAG->getConstant(31, MVT::i32));
return ISelDAG->getNode(ISD::ADD, MVT::i32, Q, T);
}
/// BuildUDIVSequence - Given an ISD::UDIV 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:
/// <http://the.wall.riscom.net/books/proc/ppc/cwg/code2.html>
SDOperand ISel::BuildUDIVSequence(SDOperand N) {
unsigned d =
(unsigned)cast<ConstantSDNode>(N.getOperand(1))->getSignExtended();
mu magics = magicu(d);
// Multiply the numerator (operand 0) by the magic value
SDOperand Q = ISelDAG->getNode(ISD::MULHU, MVT::i32, N.getOperand(0),
ISelDAG->getConstant(magics.m, MVT::i32));
if (magics.a == 0) {
Q = ISelDAG->getNode(ISD::SRL, MVT::i32, Q,
ISelDAG->getConstant(magics.s, MVT::i32));
} else {
SDOperand NPQ = ISelDAG->getNode(ISD::SUB, MVT::i32, N.getOperand(0), Q);
NPQ = ISelDAG->getNode(ISD::SRL, MVT::i32, NPQ,
ISelDAG->getConstant(1, MVT::i32));
NPQ = ISelDAG->getNode(ISD::ADD, MVT::i32, NPQ, Q);
Q = ISelDAG->getNode(ISD::SRL, MVT::i32, NPQ,
ISelDAG->getConstant(magics.s-1, MVT::i32));
}
return Q;
}
/// getGlobalBaseReg - Output the instructions required to put the
@ -1395,19 +1250,10 @@ unsigned ISel::SelectExpr(SDOperand N, bool Recording) {
BuildMI(BB, PPC::ADDZE, 1, Tmp4).addReg(Tmp1);
BuildMI(BB, PPC::NEG, 1, Result).addReg(Tmp4);
return Result;
} else if (Tmp3) {
ExprMap.erase(N);
return SelectExpr(BuildSDIVSequence(N));
}
}
// fall thru
case ISD::UDIV:
// If this is a divide by constant, we can emit code using some magic
// constants to implement it as a multiply instead.
if (isIntImmediate(N.getOperand(1), Tmp3) && Tmp3) {
ExprMap.erase(N);
return SelectExpr(BuildUDIVSequence(N));
}
Tmp1 = SelectExpr(N.getOperand(0));
Tmp2 = SelectExpr(N.getOperand(1));
Opc = (ISD::UDIV == opcode) ? PPC::DIVWU : PPC::DIVW; break;