[llvm-commits] CVS: llvm/utils/BuildShuffleTable/BuildShuffleTable.cpp Makefile
Chris Lattner
lattner at cs.uiuc.edu
Sun Apr 16 17:30:53 PDT 2006
Changes in directory llvm/utils/BuildShuffleTable:
BuildShuffleTable.cpp added (r1.1)
Makefile added (r1.1)
---
Log message:
Initial checking of a perfect shuffle generation program for 4-element
Altivec vectors.
---
Diffs of the changes: (+487 -0)
BuildShuffleTable.cpp | 474 ++++++++++++++++++++++++++++++++++++++++++++++++++
Makefile | 13 +
2 files changed, 487 insertions(+)
Index: llvm/utils/BuildShuffleTable/BuildShuffleTable.cpp
diff -c /dev/null llvm/utils/BuildShuffleTable/BuildShuffleTable.cpp:1.1
*** /dev/null Sun Apr 16 19:30:51 2006
--- llvm/utils/BuildShuffleTable/BuildShuffleTable.cpp Sun Apr 16 19:30:41 2006
***************
*** 0 ****
--- 1,474 ----
+ //===-- 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");
+
Index: llvm/utils/BuildShuffleTable/Makefile
diff -c /dev/null llvm/utils/BuildShuffleTable/Makefile:1.1
*** /dev/null Sun Apr 16 19:30:53 2006
--- llvm/utils/BuildShuffleTable/Makefile Sun Apr 16 19:30:41 2006
***************
*** 0 ****
--- 1,13 ----
+ ##===- 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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