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Initial checking of a perfect shuffle generation program for 4-element

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Altivec vectors.

llvm-svn: 27736
This commit is contained in:
Chris Lattner 2006-04-17 00:30:41 +00:00
parent 087af2ecda
commit a6a36551d3
2 changed files with 487 additions and 0 deletions
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13
utils/PerfectShuffle/Makefile Normal file
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##===- utils/BuildShuffleTable/Makefile --------------------*- Makefile -*-===##
#
# The LLVM Compiler Infrastructure
#
# This file was developed by Chris Lattner and is distributed under
# the University of Illinois Open Source License. See LICENSE.TXT for details.
#
##===----------------------------------------------------------------------===##
LEVEL = ../..
TOOLNAME = llvm-BuildShuffleTable
include $(LEVEL)/Makefile.common

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utils/PerfectShuffle/PerfectShuffle.cpp Normal file
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//===-- BuildShuffleTable.cpp - Perfect Shuffle Generator -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Chris Lattner and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file computes an optimal sequence of instructions for doing all shuffles
// of two 4-element vectors. With a release build and when configured to emit
// an altivec instruction table, this takes about 30s to run on a 2.7Ghz
// PowerPC G5.
//
//===----------------------------------------------------------------------===//
#include <iostream>
#include <vector>
struct Operator;
// Masks are 4-nibble hex numbers. Values 0-7 in any nibble means that it takes
// an element from that value of the input vectors. A value of 8 means the
// entry is undefined.
// Mask manipulation functions.
static inline unsigned short MakeMask(unsigned V0, unsigned V1,
unsigned V2, unsigned V3) {
return (V0 << (3*4)) | (V1 << (2*4)) | (V2 << (1*4)) | (V3 << (0*4));
}
/// getMaskElt - Return element N of the specified mask.
static unsigned getMaskElt(unsigned Mask, unsigned Elt) {
return (Mask >> ((3-Elt)*4)) & 0xF;
}
static unsigned setMaskElt(unsigned Mask, unsigned Elt, unsigned NewVal) {
unsigned FieldShift = ((3-Elt)*4);
return (Mask & ~(0xF << FieldShift)) | (NewVal << FieldShift);
}
// Reject elements where the values are 9-15.
static bool isValidMask(unsigned short Mask) {
unsigned short UndefBits = Mask & 0x8888;
return (Mask & ((UndefBits >> 1)|(UndefBits>>2)|(UndefBits>>3))) == 0;
}
/// hasUndefElements - Return true if any of the elements in the mask are undefs
///
static bool hasUndefElements(unsigned short Mask) {
return (Mask & 0x8888) != 0;
}
/// isOnlyLHSMask - Return true if this mask only refers to its LHS, not
/// including undef values..
static bool isOnlyLHSMask(unsigned short Mask) {
return (Mask & 0x4444) == 0;
}
/// getLHSOnlyMask - Given a mask that refers to its LHS and RHS, modify it to
/// refer to the LHS only (for when one argument value is passed into the same
/// function twice).
static unsigned short getLHSOnlyMask(unsigned short Mask) {
return Mask & 0xBBBB; // Keep only LHS and Undefs.
}
/// getCompressedMask - Turn a 16-bit uncompressed mask (where each elt uses 4
/// bits) into a compressed 13-bit mask, where each elt is multiplied by 9.
static unsigned getCompressedMask(unsigned short Mask) {
return getMaskElt(Mask, 0)*9*9*9 + getMaskElt(Mask, 1)*9*9 +
getMaskElt(Mask, 2)*9 + getMaskElt(Mask, 3);
}
static void PrintMask(unsigned i, std::ostream &OS) {
OS << "<" << (char)(getMaskElt(i, 0) == 8 ? 'u' : ('0'+getMaskElt(i, 0)))
<< "," << (char)(getMaskElt(i, 1) == 8 ? 'u' : ('0'+getMaskElt(i, 1)))
<< "," << (char)(getMaskElt(i, 2) == 8 ? 'u' : ('0'+getMaskElt(i, 2)))
<< "," << (char)(getMaskElt(i, 3) == 8 ? 'u' : ('0'+getMaskElt(i, 3)))
<< ">";
}
/// ShuffleVal - This represents a shufflevector operation.
struct ShuffleVal {
unsigned Cost; // Number of instrs used to generate this value.
Operator *Op; // The Operation used to generate this value.
unsigned short Arg0, Arg1; // Input operands for this value.
ShuffleVal() : Cost(1000000) {}
};
/// ShufTab - This is the actual shuffle table that we are trying to generate.
///
static ShuffleVal ShufTab[65536];
/// TheOperators - All of the operators that this target supports.
static std::vector<Operator*> TheOperators;
/// Operator - This is a vector operation that is available for use.
struct Operator {
unsigned short ShuffleMask;
unsigned short OpNum;
const char *Name;
Operator(unsigned short shufflemask, const char *name)
: ShuffleMask(shufflemask), Name(name) {
OpNum = TheOperators.size();
TheOperators.push_back(this);
}
~Operator() {
assert(TheOperators.back() == this);
TheOperators.pop_back();
}
bool isOnlyLHSOperator() const {
return isOnlyLHSMask(ShuffleMask);
}
const char *getName() const { return Name; }
unsigned short getTransformedMask(unsigned short LHSMask, unsigned RHSMask) {
// Extract the elements from LHSMask and RHSMask, as appropriate.
unsigned Result = 0;
for (unsigned i = 0; i != 4; ++i) {
unsigned SrcElt = (ShuffleMask >> (4*i)) & 0xF;
unsigned ResElt;
if (SrcElt < 4)
ResElt = getMaskElt(LHSMask, SrcElt);
else if (SrcElt < 8)
ResElt = getMaskElt(RHSMask, SrcElt-4);
else {
assert(SrcElt == 8 && "Bad src elt!");
ResElt = 8;
}
Result |= ResElt << (4*i);
}
return Result;
}
};
static const char *getZeroCostOpName(unsigned short Op) {
if (ShufTab[Op].Arg0 == 0x0123)
return "LHS";
else if (ShufTab[Op].Arg0 == 0x4567)
return "RHS";
else {
assert(0 && "bad zero cost operation");
abort();
}
}
static void PrintOperation(unsigned ValNo, unsigned short Vals[]) {
unsigned short ThisOp = Vals[ValNo];
std::cerr << "t" << ValNo;
PrintMask(ThisOp, std::cerr);
std::cerr << " = " << ShufTab[ThisOp].Op->getName() << "(";
if (ShufTab[ShufTab[ThisOp].Arg0].Cost == 0) {
std::cerr << getZeroCostOpName(ShufTab[ThisOp].Arg0);
PrintMask(ShufTab[ThisOp].Arg0, std::cerr);
} else {
// Figure out what tmp # it is.
for (unsigned i = 0; ; ++i)
if (Vals[i] == ShufTab[ThisOp].Arg0) {
std::cerr << "t" << i;
break;
}
}
if (!ShufTab[Vals[ValNo]].Op->isOnlyLHSOperator()) {
std::cerr << ", ";
if (ShufTab[ShufTab[ThisOp].Arg1].Cost == 0) {
std::cerr << getZeroCostOpName(ShufTab[ThisOp].Arg1);
PrintMask(ShufTab[ThisOp].Arg1, std::cerr);
} else {
// Figure out what tmp # it is.
for (unsigned i = 0; ; ++i)
if (Vals[i] == ShufTab[ThisOp].Arg1) {
std::cerr << "t" << i;
break;
}
}
}
std::cerr << ") ";
}
static unsigned getNumEntered() {
unsigned Count = 0;
for (unsigned i = 0; i != 65536; ++i)
Count += ShufTab[i].Cost < 100;
return Count;
}
static void EvaluateOps(unsigned short Elt, unsigned short Vals[],
unsigned &NumVals) {
if (ShufTab[Elt].Cost == 0) return;
// If this value has already been evaluated, it is free. FIXME: match undefs.
for (unsigned i = 0, e = NumVals; i != e; ++i)
if (Vals[i] == Elt) return;
// Otherwise, get the operands of the value, then add it.
unsigned Arg0 = ShufTab[Elt].Arg0, Arg1 = ShufTab[Elt].Arg1;
if (ShufTab[Arg0].Cost)
EvaluateOps(Arg0, Vals, NumVals);
if (Arg0 != Arg1 && ShufTab[Arg1].Cost)
EvaluateOps(Arg1, Vals, NumVals);
Vals[NumVals++] = Elt;
}
int main() {
// Seed the table with accesses to the LHS and RHS.
ShufTab[0x0123].Cost = 0;
ShufTab[0x0123].Op = 0;
ShufTab[0x0123].Arg0 = 0x0123;
ShufTab[0x4567].Cost = 0;
ShufTab[0x4567].Op = 0;
ShufTab[0x4567].Arg0 = 0x4567;
// Seed the first-level of shuffles, shuffles whose inputs are the input to
// the vectorshuffle operation.
bool MadeChange = true;
unsigned OpCount = 0;
while (MadeChange) {
MadeChange = false;
++OpCount;
std::cerr << "Starting iteration #" << OpCount << " with "
<< getNumEntered() << " entries established.\n";
// Scan the table for two reasons: First, compute the maximum cost of any
// operation left in the table. Second, make sure that values with undefs
// have the cheapest alternative that they match.
unsigned MaxCost = ShufTab[0].Cost;
for (unsigned i = 1; i != 0x8889; ++i) {
if (!isValidMask(i)) continue;
if (ShufTab[i].Cost > MaxCost)
MaxCost = ShufTab[i].Cost;
// If this value has an undef, make it be computed the cheapest possible
// way of any of the things that it matches.
if (hasUndefElements(i)) {
// This code is a little bit tricky, so here's the idea: consider some
// permutation, like 7u4u. To compute the lowest cost for 7u4u, we
// need to take the minimum cost of all of 7[0-8]4[0-8], 81 entries. If
// there are 3 undefs, the number rises to 729 entries we have to scan,
// and for the 4 undef case, we have to scan the whole table.
//
// Instead of doing this huge amount of scanning, we process the table
// entries *in order*, and use the fact that 'u' is 8, larger than any
// valid index. Given an entry like 7u4u then, we only need to scan
// 7[0-7]4u - 8 entries. We can get away with this, because we already
// know that each of 704u, 714u, 724u, etc contain the minimum value of
// all of the 704[0-8], 714[0-8] and 724[0-8] entries respectively.
unsigned UndefIdx;
if (i & 0x8000)
UndefIdx = 0;
else if (i & 0x0800)
UndefIdx = 1;
else if (i & 0x0080)
UndefIdx = 2;
else if (i & 0x0008)
UndefIdx = 3;
else
abort();
unsigned MinVal = i;
unsigned MinCost = ShufTab[i].Cost;
// Scan the 8 entries.
for (unsigned j = 0; j != 8; ++j) {
unsigned NewElt = setMaskElt(i, UndefIdx, j);
if (ShufTab[NewElt].Cost < MinCost) {
MinCost = ShufTab[NewElt].Cost;
MinVal = NewElt;
}
}
// If we found something cheaper than what was here before, use it.
if (i != MinVal) {
MadeChange = true;
ShufTab[i] = ShufTab[MinVal];
}
}
}
for (unsigned LHS = 0; LHS != 0x8889; ++LHS) {
if (!isValidMask(LHS)) continue;
if (ShufTab[LHS].Cost > 1000) continue;
// If nothing involving this operand could possibly be cheaper than what
// we already have, don't consider it.
if (ShufTab[LHS].Cost + 1 >= MaxCost)
continue;
for (unsigned opnum = 0, e = TheOperators.size(); opnum != e; ++opnum) {
Operator *Op = TheOperators[opnum];
unsigned short Mask = Op->ShuffleMask;
// Evaluate op(LHS,LHS)
unsigned ResultMask = Op->getTransformedMask(LHS, LHS);
unsigned Cost = ShufTab[LHS].Cost + 1;
if (Cost < ShufTab[ResultMask].Cost) {
ShufTab[ResultMask].Cost = Cost;
ShufTab[ResultMask].Op = Op;
ShufTab[ResultMask].Arg0 = LHS;
ShufTab[ResultMask].Arg1 = LHS;
MadeChange = true;
}
// If this is a two input instruction, include the op(x,y) cases. If
// this is a one input instruction, skip this.
if (Op->isOnlyLHSOperator()) continue;
for (unsigned RHS = 0; RHS != 0x8889; ++RHS) {
if (!isValidMask(RHS)) continue;
if (ShufTab[RHS].Cost > 1000) continue;
// If nothing involving this operand could possibly be cheaper than
// what we already have, don't consider it.
if (ShufTab[RHS].Cost + 1 >= MaxCost)
continue;
// Evaluate op(LHS,RHS)
unsigned ResultMask = Op->getTransformedMask(LHS, RHS);
if (ShufTab[ResultMask].Cost <= OpCount ||
ShufTab[ResultMask].Cost <= ShufTab[LHS].Cost ||
ShufTab[ResultMask].Cost <= ShufTab[RHS].Cost)
continue;
// Figure out the cost to evaluate this, knowing that CSE's only need
// to be evaluated once.
unsigned short Vals[30];
unsigned NumVals = 0;
EvaluateOps(LHS, Vals, NumVals);
EvaluateOps(RHS, Vals, NumVals);
unsigned Cost = NumVals + 1;
if (Cost < ShufTab[ResultMask].Cost) {
ShufTab[ResultMask].Cost = Cost;
ShufTab[ResultMask].Op = Op;
ShufTab[ResultMask].Arg0 = LHS;
ShufTab[ResultMask].Arg1 = RHS;
MadeChange = true;
}
}
}
}
}
std::cerr << "Finished Table has " << getNumEntered()
<< " entries established.\n";
unsigned CostArray[10] = { 0 };
// Compute a cost histogram.
for (unsigned i = 0; i != 65536; ++i) {
if (!isValidMask(i)) continue;
if (ShufTab[i].Cost > 9)
++CostArray[9];
else
++CostArray[ShufTab[i].Cost];
}
for (unsigned i = 0; i != 9; ++i)
if (CostArray[i])
std::cout << "// " << CostArray[i] << " entries have cost " << i << "\n";
if (CostArray[9])
std::cout << "// " << CostArray[9] << " entries have higher cost!\n";
// Build up the table to emit.
std::cout << "\n// This table is 6561*4 = 26244 bytes in size.\n";
std::cout << "static const unsigned InstrTab[6561+1] = {\n";
for (unsigned i = 0; i != 0x8889; ++i) {
if (!isValidMask(i)) continue;
// CostSat - The cost of this operation saturated to two bits.
unsigned CostSat = ShufTab[i].Cost;
if (CostSat > 3) CostSat = 3;
unsigned OpNum = ShufTab[i].Op ? ShufTab[i].Op->OpNum : 0;
assert(OpNum < 16 && "Too few bits to encode operation!");
unsigned LHS = getCompressedMask(ShufTab[i].Arg0);
unsigned RHS = getCompressedMask(ShufTab[i].Arg1);
// Encode this as 2 bits of saturated cost, 4 bits of opcodes, 13 bits of
// LHS, and 13 bits of RHS = 32 bits.
unsigned Val = (CostSat << 30) | (OpNum << 27) | (LHS << 13) | RHS;
std::cout << " " << Val << "U,\t// ";
PrintMask(i, std::cout);
std::cout << ": Cost " << ShufTab[i].Cost;
std::cout << " " << (ShufTab[i].Op ? ShufTab[i].Op->getName() : "copy");
std::cout << " ";
if (ShufTab[ShufTab[i].Arg0].Cost == 0) {
std::cout << getZeroCostOpName(ShufTab[i].Arg0);
} else {
PrintMask(ShufTab[i].Arg0, std::cout);
}
if (ShufTab[i].Op && !ShufTab[i].Op->isOnlyLHSOperator()) {
std::cout << ", ";
if (ShufTab[ShufTab[i].Arg1].Cost == 0) {
std::cout << getZeroCostOpName(ShufTab[i].Arg1);
} else {
PrintMask(ShufTab[i].Arg1, std::cout);
}
}
std::cout << "\n";
}
std::cout << " 0\n};\n";
if (0) {
// Print out the table.
for (unsigned i = 0; i != 0x8889; ++i) {
if (!isValidMask(i)) continue;
if (ShufTab[i].Cost < 1000) {
PrintMask(i, std::cerr);
std::cerr << " - Cost " << ShufTab[i].Cost << " - ";
unsigned short Vals[30];
unsigned NumVals = 0;
EvaluateOps(i, Vals, NumVals);
for (unsigned j = 0, e = NumVals; j != e; ++j)
PrintOperation(j, Vals);
std::cerr << "\n";
}
}
}
}
///===---------------------------------------------------------------------===//
/// The altivec instruction definitions. This is the altivec-specific part of
/// this file.
///===---------------------------------------------------------------------===//
struct vmrghw : public Operator {
vmrghw() : Operator(0x0415, "vmrghw") {}
} the_vmrghw;
struct vmrglw : public Operator {
vmrglw() : Operator(0x2637, "vmrglw") {}
} the_vmrglw;
template<unsigned Elt>
struct vspltisw : public Operator {
vspltisw(const char *N) : Operator(MakeMask(Elt, Elt, Elt, Elt), N) {}
};
vspltisw<0> the_vspltisw0("vspltisw0");
vspltisw<1> the_vspltisw1("vspltisw1");
vspltisw<2> the_vspltisw2("vspltisw2");
vspltisw<3> the_vspltisw3("vspltisw3");
template<unsigned N>
struct vsldoi : public Operator {
vsldoi(const char *n) : Operator(MakeMask(N&7, (N+1)&7, (N+2)&7, (N+3)&7), n){
}
};
vsldoi<1> the_vsldoi1("vsldoi4");
vsldoi<2> the_vsldoi2("vsldoi8");
vsldoi<3> the_vsldoi3("vsldoi12");