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Initial checking of a perfect shuffle generation program for 4-element
Altivec vectors. llvm-svn: 27736
This commit is contained in:
Chris Lattner
parent
087af2ecda
commit
a6a36551d3
13
utils/PerfectShuffle/Makefile
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13
utils/PerfectShuffle/Makefile
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##===- utils/BuildShuffleTable/Makefile --------------------*- Makefile -*-===##
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#
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# The LLVM Compiler Infrastructure
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#
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# This file was developed by Chris Lattner and is distributed under
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# the University of Illinois Open Source License. See LICENSE.TXT for details.
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#
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##===----------------------------------------------------------------------===##
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LEVEL = ../..
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TOOLNAME = llvm-BuildShuffleTable
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include $(LEVEL)/Makefile.common
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474
utils/PerfectShuffle/PerfectShuffle.cpp
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474
utils/PerfectShuffle/PerfectShuffle.cpp
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//===-- BuildShuffleTable.cpp - Perfect Shuffle Generator -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Chris Lattner and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file computes an optimal sequence of instructions for doing all shuffles
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// of two 4-element vectors. With a release build and when configured to emit
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// an altivec instruction table, this takes about 30s to run on a 2.7Ghz
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// PowerPC G5.
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//
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//===----------------------------------------------------------------------===//
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#include <iostream>
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#include <vector>
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struct Operator;
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// Masks are 4-nibble hex numbers. Values 0-7 in any nibble means that it takes
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// an element from that value of the input vectors. A value of 8 means the
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// entry is undefined.
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// Mask manipulation functions.
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static inline unsigned short MakeMask(unsigned V0, unsigned V1,
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unsigned V2, unsigned V3) {
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return (V0 << (3*4)) | (V1 << (2*4)) | (V2 << (1*4)) | (V3 << (0*4));
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}
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/// getMaskElt - Return element N of the specified mask.
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static unsigned getMaskElt(unsigned Mask, unsigned Elt) {
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return (Mask >> ((3-Elt)*4)) & 0xF;
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}
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static unsigned setMaskElt(unsigned Mask, unsigned Elt, unsigned NewVal) {
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unsigned FieldShift = ((3-Elt)*4);
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return (Mask & ~(0xF << FieldShift)) | (NewVal << FieldShift);
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}
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// Reject elements where the values are 9-15.
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static bool isValidMask(unsigned short Mask) {
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unsigned short UndefBits = Mask & 0x8888;
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return (Mask & ((UndefBits >> 1)|(UndefBits>>2)|(UndefBits>>3))) == 0;
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}
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/// hasUndefElements - Return true if any of the elements in the mask are undefs
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///
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static bool hasUndefElements(unsigned short Mask) {
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return (Mask & 0x8888) != 0;
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}
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/// isOnlyLHSMask - Return true if this mask only refers to its LHS, not
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/// including undef values..
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static bool isOnlyLHSMask(unsigned short Mask) {
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return (Mask & 0x4444) == 0;
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}
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/// getLHSOnlyMask - Given a mask that refers to its LHS and RHS, modify it to
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/// refer to the LHS only (for when one argument value is passed into the same
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/// function twice).
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static unsigned short getLHSOnlyMask(unsigned short Mask) {
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return Mask & 0xBBBB; // Keep only LHS and Undefs.
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}
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/// getCompressedMask - Turn a 16-bit uncompressed mask (where each elt uses 4
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/// bits) into a compressed 13-bit mask, where each elt is multiplied by 9.
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static unsigned getCompressedMask(unsigned short Mask) {
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return getMaskElt(Mask, 0)*9*9*9 + getMaskElt(Mask, 1)*9*9 +
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getMaskElt(Mask, 2)*9 + getMaskElt(Mask, 3);
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}
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static void PrintMask(unsigned i, std::ostream &OS) {
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OS << "<" << (char)(getMaskElt(i, 0) == 8 ? 'u' : ('0'+getMaskElt(i, 0)))
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<< "," << (char)(getMaskElt(i, 1) == 8 ? 'u' : ('0'+getMaskElt(i, 1)))
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<< "," << (char)(getMaskElt(i, 2) == 8 ? 'u' : ('0'+getMaskElt(i, 2)))
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<< "," << (char)(getMaskElt(i, 3) == 8 ? 'u' : ('0'+getMaskElt(i, 3)))
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<< ">";
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}
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/// ShuffleVal - This represents a shufflevector operation.
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struct ShuffleVal {
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unsigned Cost; // Number of instrs used to generate this value.
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Operator *Op; // The Operation used to generate this value.
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unsigned short Arg0, Arg1; // Input operands for this value.
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ShuffleVal() : Cost(1000000) {}
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};
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/// ShufTab - This is the actual shuffle table that we are trying to generate.
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///
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static ShuffleVal ShufTab[65536];
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/// TheOperators - All of the operators that this target supports.
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static std::vector<Operator*> TheOperators;
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/// Operator - This is a vector operation that is available for use.
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struct Operator {
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unsigned short ShuffleMask;
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unsigned short OpNum;
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const char *Name;
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Operator(unsigned short shufflemask, const char *name)
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: ShuffleMask(shufflemask), Name(name) {
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OpNum = TheOperators.size();
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TheOperators.push_back(this);
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}
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~Operator() {
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assert(TheOperators.back() == this);
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TheOperators.pop_back();
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}
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bool isOnlyLHSOperator() const {
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return isOnlyLHSMask(ShuffleMask);
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}
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const char *getName() const { return Name; }
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unsigned short getTransformedMask(unsigned short LHSMask, unsigned RHSMask) {
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// Extract the elements from LHSMask and RHSMask, as appropriate.
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unsigned Result = 0;
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for (unsigned i = 0; i != 4; ++i) {
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unsigned SrcElt = (ShuffleMask >> (4*i)) & 0xF;
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unsigned ResElt;
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if (SrcElt < 4)
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ResElt = getMaskElt(LHSMask, SrcElt);
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else if (SrcElt < 8)
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ResElt = getMaskElt(RHSMask, SrcElt-4);
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else {
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assert(SrcElt == 8 && "Bad src elt!");
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ResElt = 8;
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}
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Result |= ResElt << (4*i);
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}
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return Result;
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}
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};
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static const char *getZeroCostOpName(unsigned short Op) {
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if (ShufTab[Op].Arg0 == 0x0123)
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return "LHS";
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else if (ShufTab[Op].Arg0 == 0x4567)
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return "RHS";
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else {
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assert(0 && "bad zero cost operation");
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abort();
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}
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}
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static void PrintOperation(unsigned ValNo, unsigned short Vals[]) {
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unsigned short ThisOp = Vals[ValNo];
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std::cerr << "t" << ValNo;
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PrintMask(ThisOp, std::cerr);
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std::cerr << " = " << ShufTab[ThisOp].Op->getName() << "(";
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if (ShufTab[ShufTab[ThisOp].Arg0].Cost == 0) {
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std::cerr << getZeroCostOpName(ShufTab[ThisOp].Arg0);
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PrintMask(ShufTab[ThisOp].Arg0, std::cerr);
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} else {
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// Figure out what tmp # it is.
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for (unsigned i = 0; ; ++i)
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if (Vals[i] == ShufTab[ThisOp].Arg0) {
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std::cerr << "t" << i;
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break;
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}
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}
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if (!ShufTab[Vals[ValNo]].Op->isOnlyLHSOperator()) {
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std::cerr << ", ";
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if (ShufTab[ShufTab[ThisOp].Arg1].Cost == 0) {
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std::cerr << getZeroCostOpName(ShufTab[ThisOp].Arg1);
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PrintMask(ShufTab[ThisOp].Arg1, std::cerr);
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} else {
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// Figure out what tmp # it is.
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for (unsigned i = 0; ; ++i)
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if (Vals[i] == ShufTab[ThisOp].Arg1) {
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std::cerr << "t" << i;
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break;
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}
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}
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}
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std::cerr << ") ";
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}
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static unsigned getNumEntered() {
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unsigned Count = 0;
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for (unsigned i = 0; i != 65536; ++i)
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Count += ShufTab[i].Cost < 100;
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return Count;
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}
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static void EvaluateOps(unsigned short Elt, unsigned short Vals[],
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unsigned &NumVals) {
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if (ShufTab[Elt].Cost == 0) return;
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// If this value has already been evaluated, it is free. FIXME: match undefs.
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for (unsigned i = 0, e = NumVals; i != e; ++i)
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if (Vals[i] == Elt) return;
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// Otherwise, get the operands of the value, then add it.
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unsigned Arg0 = ShufTab[Elt].Arg0, Arg1 = ShufTab[Elt].Arg1;
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if (ShufTab[Arg0].Cost)
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EvaluateOps(Arg0, Vals, NumVals);
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if (Arg0 != Arg1 && ShufTab[Arg1].Cost)
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EvaluateOps(Arg1, Vals, NumVals);
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Vals[NumVals++] = Elt;
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}
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int main() {
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// Seed the table with accesses to the LHS and RHS.
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ShufTab[0x0123].Cost = 0;
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ShufTab[0x0123].Op = 0;
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ShufTab[0x0123].Arg0 = 0x0123;
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ShufTab[0x4567].Cost = 0;
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ShufTab[0x4567].Op = 0;
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ShufTab[0x4567].Arg0 = 0x4567;
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// Seed the first-level of shuffles, shuffles whose inputs are the input to
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// the vectorshuffle operation.
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bool MadeChange = true;
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unsigned OpCount = 0;
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while (MadeChange) {
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MadeChange = false;
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++OpCount;
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std::cerr << "Starting iteration #" << OpCount << " with "
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<< getNumEntered() << " entries established.\n";
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// Scan the table for two reasons: First, compute the maximum cost of any
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// operation left in the table. Second, make sure that values with undefs
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// have the cheapest alternative that they match.
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unsigned MaxCost = ShufTab[0].Cost;
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for (unsigned i = 1; i != 0x8889; ++i) {
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if (!isValidMask(i)) continue;
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if (ShufTab[i].Cost > MaxCost)
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MaxCost = ShufTab[i].Cost;
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// If this value has an undef, make it be computed the cheapest possible
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// way of any of the things that it matches.
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if (hasUndefElements(i)) {
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// This code is a little bit tricky, so here's the idea: consider some
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// permutation, like 7u4u. To compute the lowest cost for 7u4u, we
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// need to take the minimum cost of all of 7[0-8]4[0-8], 81 entries. If
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// there are 3 undefs, the number rises to 729 entries we have to scan,
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// and for the 4 undef case, we have to scan the whole table.
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//
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// Instead of doing this huge amount of scanning, we process the table
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// entries *in order*, and use the fact that 'u' is 8, larger than any
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// valid index. Given an entry like 7u4u then, we only need to scan
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// 7[0-7]4u - 8 entries. We can get away with this, because we already
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// know that each of 704u, 714u, 724u, etc contain the minimum value of
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// all of the 704[0-8], 714[0-8] and 724[0-8] entries respectively.
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unsigned UndefIdx;
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if (i & 0x8000)
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UndefIdx = 0;
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else if (i & 0x0800)
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UndefIdx = 1;
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else if (i & 0x0080)
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UndefIdx = 2;
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else if (i & 0x0008)
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UndefIdx = 3;
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else
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abort();
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unsigned MinVal = i;
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unsigned MinCost = ShufTab[i].Cost;
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// Scan the 8 entries.
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for (unsigned j = 0; j != 8; ++j) {
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unsigned NewElt = setMaskElt(i, UndefIdx, j);
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if (ShufTab[NewElt].Cost < MinCost) {
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MinCost = ShufTab[NewElt].Cost;
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MinVal = NewElt;
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}
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}
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// If we found something cheaper than what was here before, use it.
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if (i != MinVal) {
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MadeChange = true;
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ShufTab[i] = ShufTab[MinVal];
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}
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}
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}
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for (unsigned LHS = 0; LHS != 0x8889; ++LHS) {
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if (!isValidMask(LHS)) continue;
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if (ShufTab[LHS].Cost > 1000) continue;
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// If nothing involving this operand could possibly be cheaper than what
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// we already have, don't consider it.
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if (ShufTab[LHS].Cost + 1 >= MaxCost)
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continue;
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for (unsigned opnum = 0, e = TheOperators.size(); opnum != e; ++opnum) {
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Operator *Op = TheOperators[opnum];
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unsigned short Mask = Op->ShuffleMask;
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// Evaluate op(LHS,LHS)
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unsigned ResultMask = Op->getTransformedMask(LHS, LHS);
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unsigned Cost = ShufTab[LHS].Cost + 1;
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if (Cost < ShufTab[ResultMask].Cost) {
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ShufTab[ResultMask].Cost = Cost;
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ShufTab[ResultMask].Op = Op;
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ShufTab[ResultMask].Arg0 = LHS;
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ShufTab[ResultMask].Arg1 = LHS;
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MadeChange = true;
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}
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// If this is a two input instruction, include the op(x,y) cases. If
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// this is a one input instruction, skip this.
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if (Op->isOnlyLHSOperator()) continue;
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for (unsigned RHS = 0; RHS != 0x8889; ++RHS) {
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if (!isValidMask(RHS)) continue;
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if (ShufTab[RHS].Cost > 1000) continue;
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// If nothing involving this operand could possibly be cheaper than
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// what we already have, don't consider it.
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if (ShufTab[RHS].Cost + 1 >= MaxCost)
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continue;
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// Evaluate op(LHS,RHS)
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unsigned ResultMask = Op->getTransformedMask(LHS, RHS);
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if (ShufTab[ResultMask].Cost <= OpCount ||
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ShufTab[ResultMask].Cost <= ShufTab[LHS].Cost ||
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ShufTab[ResultMask].Cost <= ShufTab[RHS].Cost)
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continue;
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// Figure out the cost to evaluate this, knowing that CSE's only need
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// to be evaluated once.
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unsigned short Vals[30];
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unsigned NumVals = 0;
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EvaluateOps(LHS, Vals, NumVals);
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EvaluateOps(RHS, Vals, NumVals);
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unsigned Cost = NumVals + 1;
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if (Cost < ShufTab[ResultMask].Cost) {
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ShufTab[ResultMask].Cost = Cost;
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ShufTab[ResultMask].Op = Op;
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ShufTab[ResultMask].Arg0 = LHS;
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ShufTab[ResultMask].Arg1 = RHS;
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MadeChange = true;
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}
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}
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}
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}
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}
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std::cerr << "Finished Table has " << getNumEntered()
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<< " entries established.\n";
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unsigned CostArray[10] = { 0 };
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// Compute a cost histogram.
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for (unsigned i = 0; i != 65536; ++i) {
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if (!isValidMask(i)) continue;
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if (ShufTab[i].Cost > 9)
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++CostArray[9];
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else
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++CostArray[ShufTab[i].Cost];
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}
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for (unsigned i = 0; i != 9; ++i)
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if (CostArray[i])
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std::cout << "// " << CostArray[i] << " entries have cost " << i << "\n";
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if (CostArray[9])
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std::cout << "// " << CostArray[9] << " entries have higher cost!\n";
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// Build up the table to emit.
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std::cout << "\n// This table is 6561*4 = 26244 bytes in size.\n";
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std::cout << "static const unsigned InstrTab[6561+1] = {\n";
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for (unsigned i = 0; i != 0x8889; ++i) {
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if (!isValidMask(i)) continue;
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// CostSat - The cost of this operation saturated to two bits.
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unsigned CostSat = ShufTab[i].Cost;
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if (CostSat > 3) CostSat = 3;
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unsigned OpNum = ShufTab[i].Op ? ShufTab[i].Op->OpNum : 0;
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assert(OpNum < 16 && "Too few bits to encode operation!");
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unsigned LHS = getCompressedMask(ShufTab[i].Arg0);
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unsigned RHS = getCompressedMask(ShufTab[i].Arg1);
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// Encode this as 2 bits of saturated cost, 4 bits of opcodes, 13 bits of
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// LHS, and 13 bits of RHS = 32 bits.
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unsigned Val = (CostSat << 30) | (OpNum << 27) | (LHS << 13) | RHS;
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std::cout << " " << Val << "U,\t// ";
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PrintMask(i, std::cout);
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std::cout << ": Cost " << ShufTab[i].Cost;
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std::cout << " " << (ShufTab[i].Op ? ShufTab[i].Op->getName() : "copy");
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std::cout << " ";
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if (ShufTab[ShufTab[i].Arg0].Cost == 0) {
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std::cout << getZeroCostOpName(ShufTab[i].Arg0);
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} else {
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PrintMask(ShufTab[i].Arg0, std::cout);
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}
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if (ShufTab[i].Op && !ShufTab[i].Op->isOnlyLHSOperator()) {
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std::cout << ", ";
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if (ShufTab[ShufTab[i].Arg1].Cost == 0) {
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std::cout << getZeroCostOpName(ShufTab[i].Arg1);
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} else {
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PrintMask(ShufTab[i].Arg1, std::cout);
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}
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}
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std::cout << "\n";
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}
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std::cout << " 0\n};\n";
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if (0) {
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// Print out the table.
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for (unsigned i = 0; i != 0x8889; ++i) {
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if (!isValidMask(i)) continue;
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if (ShufTab[i].Cost < 1000) {
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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");
|
||||
|
||||
Loading…
Reference in New Issue
Block a user