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/*
* Copyright (C) 2016-2019 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "AirEmitShuffle.h"
#if ENABLE(B3_JIT)
#include "AirCode.h"
#include "AirInstInlines.h"
#include <wtf/GraphNodeWorklist.h>
#include <wtf/ListDump.h>
namespace JSC { namespace B3 { namespace Air {
namespace {
namespace AirEmitShuffleInternal {
static constexpr bool verbose = false;
}
template<typename Functor>
Tmp findPossibleScratch(Code& code, Bank bank, const Functor& functor) {
for (Reg reg : code.regsInPriorityOrder(bank)) {
Tmp tmp(reg);
if (functor(tmp))
return tmp;
}
return Tmp();
}
Tmp findPossibleScratch(Code& code, Bank bank, const Arg& arg1, const Arg& arg2) {
return findPossibleScratch(
code, bank,
[&] (Tmp tmp) -> bool {
return !arg1.usesTmp(tmp) && !arg2.usesTmp(tmp);
});
}
// Example: (a => b, b => a, a => c, b => d)
struct Rotate {
Vector<ShufflePair> loop; // in the example, this is the loop: (a => b, b => a)
Vector<ShufflePair> fringe; // in the example, these are the associated shifts: (a => c, b => d)
};
} // anonymous namespace
Bank ShufflePair::bank() const
{
if (src().isMemory() && dst().isMemory() && width() > pointerWidth()) {
// 8-byte memory-to-memory moves on a 32-bit platform are best handled as float moves.
return FP;
}
if (src().isGP() && dst().isGP()) {
// This means that gpPairs gets memory-to-memory shuffles. The assumption is that we
// can do that more efficiently using GPRs, except in the special case above.
return GP;
}
return FP;
}
Vector<Inst, 2> ShufflePair::insts(Code& code, Value* origin) const
{
if (UNLIKELY(src().isMemory() && dst().isMemory()))
return { Inst(moveFor(bank(), width()), origin, src(), dst(), code.newTmp(bank())) };
if (isValidForm(moveFor(bank(), width()), src().kind(), dst().kind()))
return { Inst(moveFor(bank(), width()), origin, src(), dst()) };
// We must be a store immediate or a move immediate if we reach here. The reason:
// 1. We're not a mem->mem move, given the above check.
// 2. It's always valid to do a load from Addr into a tmp using Move/Move32/MoveFloat/MoveDouble.
ASSERT(isValidForm(moveFor(bank(), width()), Arg::Addr, Arg::Tmp));
// 3. It's also always valid to do a Tmp->Tmp move.
ASSERT(isValidForm(moveFor(bank(), width()), Arg::Tmp, Arg::Tmp));
// 4. It's always valid to do a Tmp->Addr store.
ASSERT(isValidForm(moveFor(bank(), width()), Arg::Tmp, Arg::Addr));
ASSERT(src().isSomeImm());
Tmp tmp = code.newTmp(bank());
ASSERT(isValidForm(Move, Arg::BigImm, Arg::Tmp));
ASSERT(isValidForm(moveFor(bank(), width()), Arg::Tmp, dst().kind()));
return {
Inst(Move, origin, Arg::bigImm(src().value()), tmp),
Inst(moveFor(bank(), width()), origin, tmp, dst()),
};
}
void ShufflePair::dump(PrintStream& out) const
{
out.print(width(), ":", src(), "=>", dst());
}
Inst createShuffle(Value* origin, const Vector<ShufflePair>& pairs)
{
Inst result(Shuffle, origin);
for (const ShufflePair& pair : pairs)
result.append(pair.src(), pair.dst(), Arg::widthArg(pair.width()));
return result;
}
Vector<Inst> emitShuffle(
Code& code, Vector<ShufflePair> pairs, std::array<Arg, 2> scratches, Bank bank,
Value* origin)
{
if (AirEmitShuffleInternal::verbose) {
dataLog(
"Dealing with pairs: ", listDump(pairs), " and scratches ", scratches[0], ", ",
scratches[1], "\n");
}
pairs.removeAllMatching(
[&] (const ShufflePair& pair) -> bool {
return pair.src() == pair.dst();
});
// First validate that this is the kind of shuffle that we know how to deal with.
#if ASSERT_ENABLED
for (const ShufflePair& pair : pairs) {
ASSERT(pair.src().isBank(bank));
ASSERT(pair.dst().isBank(bank));
ASSERT(pair.dst().isTmp() || pair.dst().isMemory());
}
#endif // ASSERT_ENABLED
// There are two possible kinds of operations that we will do:
//
// - Shift. Example: (a => b, b => c). We emit this as "Move b, c; Move a, b". This only requires
// scratch registers if there are memory->memory moves. We want to find as many of these as
// possible because they are cheaper. Note that shifts can involve the same source mentioned
// multiple times. Example: (a => b, a => c, b => d, b => e).
//
// - Rotate. Example: (a => b, b => a). We want to emit this as "Swap a, b", but that instruction
// may not be available, in which case we may need a scratch register or a scratch memory
// location. A gnarlier example is (a => b, b => c, c => a). We can emit this as "Swap b, c;
// Swap a, b". Note that swapping has to be careful about differing widths.
//
// Note that a rotate can have "fringe". For example, we might have (a => b, b => a, a =>c,
// b => d). This has a rotate loop (a => b, b => a) and some fringe (a => c, b => d). We treat
// the whole thing as a single rotate.
//
// We will find multiple disjoint such operations. We can execute them in any order.
// We interpret these as Moves that should be executed backwards. All shifts are keyed by their
// starting source.
HashMap<Arg, Vector<ShufflePair>> shifts;
// We interpret these as Swaps over src()'s that should be executed backwards, i.e. for a list
// of size 3 we would do "Swap list[1].src(), list[2].src(); Swap list[0].src(), list[1].src()".
// Note that we actually can't do that if the widths don't match or other bad things happen.
// But, prior to executing all of that, we need to execute the fringe: the shifts comming off the
// rotate.
Vector<Rotate> rotates;
{
HashMap<Arg, Vector<ShufflePair>> mapping;
for (const ShufflePair& pair : pairs)
mapping.add(pair.src(), Vector<ShufflePair>()).iterator->value.append(pair);
Vector<ShufflePair> currentPairs;
while (!mapping.isEmpty()) {
ASSERT(currentPairs.isEmpty());
Arg originalSrc = mapping.begin()->key;
ASSERT(!shifts.contains(originalSrc));
if (AirEmitShuffleInternal::verbose)
dataLog("Processing from ", originalSrc, "\n");
GraphNodeWorklist<Arg> worklist;
worklist.push(originalSrc);
while (Arg src = worklist.pop()) {
HashMap<Arg, Vector<ShufflePair>>::iterator iter = mapping.find(src);
if (iter == mapping.end()) {
// With a shift it's possible that we previously built the tail of this shift.
// See if that's the case now.
if (AirEmitShuffleInternal::verbose)
dataLog("Trying to append shift at ", src, "\n");
currentPairs.appendVector(shifts.take(src));
continue;
}
Vector<ShufflePair> pairs = WTFMove(iter->value);
mapping.remove(iter);
for (const ShufflePair& pair : pairs) {
currentPairs.append(pair);
ASSERT(pair.src() == src);
worklist.push(pair.dst());
}
}
ASSERT(currentPairs.size());
ASSERT(currentPairs[0].src() == originalSrc);
if (AirEmitShuffleInternal::verbose)
dataLog("currentPairs = ", listDump(currentPairs), "\n");
bool isRotate = false;
for (const ShufflePair& pair : currentPairs) {
if (pair.dst() == originalSrc) {
isRotate = true;
break;
}
}
if (isRotate) {
if (AirEmitShuffleInternal::verbose)
dataLog("It's a rotate.\n");
Rotate rotate;
// The common case is that the rotate does not have fringe. The only way to
// check for this is to examine the whole rotate.
bool ok;
if (currentPairs.last().dst() == originalSrc) {
ok = true;
for (unsigned i = currentPairs.size() - 1; i--;)
ok &= currentPairs[i].dst() == currentPairs[i + 1].src();
} else
ok = false;
if (ok)
rotate.loop = WTFMove(currentPairs);
else {
// This is the slow path. The rotate has fringe.
HashMap<Arg, ShufflePair> dstMapping;
for (const ShufflePair& pair : currentPairs)
dstMapping.add(pair.dst(), pair);
ShufflePair pair = dstMapping.take(originalSrc);
for (;;) {
rotate.loop.append(pair);
auto iter = dstMapping.find(pair.src());
if (iter == dstMapping.end())
break;
pair = iter->value;
dstMapping.remove(iter);
}
rotate.loop.reverse();
// Make sure that the fringe appears in the same order as how it appeared in the
// currentPairs, since that's the DFS order.
for (const ShufflePair& pair : currentPairs) {
// But of course we only include it if it's not in the loop.
if (dstMapping.contains(pair.dst()))
rotate.fringe.append(pair);
}
}
// If the graph search terminates because we returned to the first source, then the
// pair list has to have a very particular shape.
for (unsigned i = rotate.loop.size() - 1; i--;)
ASSERT(rotate.loop[i].dst() == rotate.loop[i + 1].src());
rotates.append(WTFMove(rotate));
currentPairs.shrink(0);
} else {
if (AirEmitShuffleInternal::verbose)
dataLog("It's a shift.\n");
shifts.add(originalSrc, WTFMove(currentPairs));
}
}
}
if (AirEmitShuffleInternal::verbose) {
dataLog("Shifts:\n");
for (auto& entry : shifts)
dataLog(" ", entry.key, ": ", listDump(entry.value), "\n");
dataLog("Rotates:\n");
for (auto& rotate : rotates)
dataLog(" loop = ", listDump(rotate.loop), ", fringe = ", listDump(rotate.fringe), "\n");
}
// In the worst case, we need two scratch registers. The way we do this is that the client passes
// us what scratch registers he happens to have laying around. We will need scratch registers in
// the following cases:
//
// - Shuffle pairs where both src and dst refer to memory.
// - Rotate when no Swap instruction is available.
//
// Lucky for us, we are guaranteed to have extra scratch registers anytime we have a Shift that
// ends with a register. We search for such a register right now.
auto moveForWidth = [&] (Width width) -> Opcode {
return moveFor(bank, width);
};
Opcode conservativeMove = moveForWidth(conservativeWidth(bank));
// We will emit things in reverse. We maintain a list of packs of instructions, and then we emit
// append them together in reverse (for example the thing at the end of resultPacks is placed
// first). This is useful because the last thing we emit frees up its destination registers, so
// it affects how we emit things before it.
Vector<Vector<Inst>> resultPacks;
Vector<Inst> result;
auto commitResult = [&] () {
resultPacks.append(WTFMove(result));
};
auto getScratch = [&] (unsigned index, Tmp possibleScratch) -> Tmp {
if (scratches[index].isTmp())
return scratches[index].tmp();
if (!possibleScratch)
return Tmp();
result.append(Inst(conservativeMove, origin, possibleScratch, scratches[index]));
return possibleScratch;
};
auto returnScratch = [&] (unsigned index, Tmp tmp) {
if (Arg(tmp) != scratches[index])
result.append(Inst(conservativeMove, origin, scratches[index], tmp));
};
auto handleShiftPair = [&] (const ShufflePair& pair, unsigned scratchIndex) {
Opcode move = moveForWidth(pair.width());
if (!isValidForm(move, pair.src().kind(), pair.dst().kind())) {
Tmp scratch =
getScratch(scratchIndex, findPossibleScratch(code, bank, pair.src(), pair.dst()));
RELEASE_ASSERT(scratch);
if (isValidForm(move, pair.src().kind(), Arg::Tmp))
result.append(Inst(moveForWidth(pair.width()), origin, pair.src(), scratch));
else {
ASSERT(pair.src().isSomeImm());
ASSERT(move == Move32);
result.append(Inst(Move, origin, Arg::bigImm(pair.src().value()), scratch));
}
result.append(Inst(moveForWidth(pair.width()), origin, scratch, pair.dst()));
returnScratch(scratchIndex, scratch);
return;
}
result.append(Inst(move, origin, pair.src(), pair.dst()));
};
auto handleShift = [&] (Vector<ShufflePair>& shift) {
// FIXME: We could optimize the spill behavior of the shifter by checking if any of the
// shifts need spills. If they do, then we could try to get a register out here. Note that
// this may fail where the current strategy succeeds: out here we need a register that does
// not interfere with any of the shifts, while the current strategy only needs to find a
// scratch register that does not interfer with a particular shift. So, this optimization
// will be opportunistic: if it succeeds, then the individual shifts can use that scratch,
// otherwise they will do what they do now.
for (unsigned i = shift.size(); i--;)
handleShiftPair(shift[i], 0);
Arg lastDst = shift.last().dst();
if (lastDst.isTmp()) {
for (Arg& scratch : scratches) {
ASSERT(scratch != lastDst);
if (!scratch.isTmp()) {
scratch = lastDst;
break;
}
}
}
};
// First handle shifts whose last destination is a tmp because these free up scratch registers.
// These end up last in the final sequence, so the final destination of these shifts will be
// available as a scratch location for anything emitted prior (so, after, since we're emitting in
// reverse).
for (auto& entry : shifts) {
Vector<ShufflePair>& shift = entry.value;
if (shift.last().dst().isTmp())
handleShift(shift);
commitResult();
}
// Now handle the rest of the shifts.
for (auto& entry : shifts) {
Vector<ShufflePair>& shift = entry.value;
if (!shift.last().dst().isTmp())
handleShift(shift);
commitResult();
}
for (Rotate& rotate : rotates) {
if (!rotate.fringe.isEmpty()) {
// Make sure we do the fringe first! This won't clobber any of the registers that are
// part of the rotation.
handleShift(rotate.fringe);
}
bool canSwap = false;
Opcode swap = Oops;
Width swapWidth = Width8; // bogus value
// Currently, the swap instruction is not available for floating point on any architecture we
// support.
if (bank == GP) {
// Figure out whether we will be doing 64-bit swaps or 32-bit swaps. If we have a mix of
// widths we handle that by fixing up the relevant register with zero-extends.
swap = Swap32;
swapWidth = Width32;
bool hasMemory = false;
bool hasIndex = false;
for (ShufflePair& pair : rotate.loop) {
switch (pair.width()) {
case Width32:
break;
case Width64:
swap = Swap64;
swapWidth = Width64;
break;
default:
RELEASE_ASSERT_NOT_REACHED();
break;
}
hasMemory |= pair.src().isMemory() || pair.dst().isMemory();
hasIndex |= pair.src().isIndex() || pair.dst().isIndex();
}
canSwap = isValidForm(swap, Arg::Tmp, Arg::Tmp);
// We can totally use swaps even if there are shuffles involving memory. But, we play it
// safe in that case. There are corner cases we don't handle, and our ability to do it is
// contingent upon swap form availability.
if (hasMemory) {
canSwap &= isValidForm(swap, Arg::Tmp, Arg::Addr);
// We don't take the swapping path if there is a mix of widths and some of the
// shuffles involve memory. That gets too confusing. We might be able to relax this
// to only bail if there are subwidth pairs involving memory, but I haven't thought
// about it very hard. Anyway, this case is not common: rotates involving memory
// don't arise for function calls, and they will only happen for rotates in user code
// if some of the variables get spilled. It's hard to imagine a program that rotates
// data around in variables while also doing a combination of uint32->uint64 and
// int64->int32 casts.
for (ShufflePair& pair : rotate.loop)
canSwap &= pair.width() == swapWidth;
}
if (hasIndex)
canSwap &= isValidForm(swap, Arg::Tmp, Arg::Index);
}
if (canSwap) {
for (unsigned i = rotate.loop.size() - 1; i--;) {
Arg left = rotate.loop[i].src();
Arg right = rotate.loop[i + 1].src();
if (left.isMemory() && right.isMemory()) {
// Note that this is a super rare outcome. Rotates are rare. Spills are rare.
// Moving data between two spills is rare. To get here a lot of rare stuff has to
// all happen at once.
Tmp scratch = getScratch(0, findPossibleScratch(code, bank, left, right));
RELEASE_ASSERT(scratch);
result.append(Inst(moveForWidth(swapWidth), origin, left, scratch));
result.append(Inst(swap, origin, scratch, right));
result.append(Inst(moveForWidth(swapWidth), origin, scratch, left));
returnScratch(0, scratch);
continue;
}
if (left.isMemory())
std::swap(left, right);
result.append(Inst(swap, origin, left, right));
}
for (ShufflePair pair : rotate.loop) {
if (pair.width() == swapWidth)
continue;
RELEASE_ASSERT(pair.width() == Width32);
RELEASE_ASSERT(swapWidth == Width64);
RELEASE_ASSERT(pair.dst().isTmp());
// Need to do an extra zero extension.
result.append(Inst(Move32, origin, pair.dst(), pair.dst()));
}
} else {
// We can treat this as a shift so long as we take the last destination (i.e. first
// source) and save it first. Then we handle the first entry in the pair in the rotate
// specially, after we restore the last destination. This requires some special care to
// find a scratch register. It's possible that we have a rotate that uses the entire
// available register file.
Tmp scratch = findPossibleScratch(
code, bank,
[&] (Tmp tmp) -> bool {
for (ShufflePair pair : rotate.loop) {
if (pair.src().usesTmp(tmp))
return false;
if (pair.dst().usesTmp(tmp))
return false;
}
return true;
});
// NOTE: This is the most likely use of scratch registers.
scratch = getScratch(0, scratch);
// We may not have found a scratch register. When this happens, we can just use the spill
// slot directly.
Arg rotateSave = scratch ? Arg(scratch) : scratches[0];
handleShiftPair(
ShufflePair(rotate.loop.last().dst(), rotateSave, rotate.loop[0].width()), 1);
for (unsigned i = rotate.loop.size(); i-- > 1;)
handleShiftPair(rotate.loop[i], 1);
handleShiftPair(
ShufflePair(rotateSave, rotate.loop[0].dst(), rotate.loop[0].width()), 1);
if (scratch)
returnScratch(0, scratch);
}
commitResult();
}
ASSERT(result.isEmpty());
for (unsigned i = resultPacks.size(); i--;)
result.appendVector(resultPacks[i]);
return result;
}
Vector<Inst> emitShuffle(
Code& code, const Vector<ShufflePair>& pairs,
const std::array<Arg, 2>& gpScratch, const std::array<Arg, 2>& fpScratch,
Value* origin)
{
Vector<ShufflePair> gpPairs;
Vector<ShufflePair> fpPairs;
for (const ShufflePair& pair : pairs) {
switch (pair.bank()) {
case GP:
gpPairs.append(pair);
break;
case FP:
fpPairs.append(pair);
break;
}
}
Vector<Inst> result;
result.appendVector(emitShuffle(code, gpPairs, gpScratch, GP, origin));
result.appendVector(emitShuffle(code, fpPairs, fpScratch, FP, origin));
return result;
}
} } } // namespace JSC::B3::Air
#endif // ENABLE(B3_JIT)