blob: c98172bd7d6b6f6755769658eba988d5cc85530b [file] [log] [blame]
/*
* Copyright (C) 2015-2017 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 "B3MoveConstants.h"
#if ENABLE(B3_JIT)
#include "AirArg.h"
#include "B3BasicBlockInlines.h"
#include "B3Dominators.h"
#include "B3InsertionSetInlines.h"
#include "B3MemoryValueInlines.h"
#include "B3PhaseScope.h"
#include "B3ProcedureInlines.h"
#include "B3ValueInlines.h"
#include "B3ValueKeyInlines.h"
#include <wtf/HashMap.h>
#include <wtf/Vector.h>
namespace JSC { namespace B3 {
namespace {
class MoveConstants {
public:
MoveConstants(Procedure& proc)
: m_proc(proc)
, m_insertionSet(proc)
{
}
void run()
{
hoistConstants(
[&] (const ValueKey& key) -> bool {
return key.opcode() == ConstFloat || key.opcode() == ConstDouble;
});
lowerFPConstants();
hoistConstants(
[&] (const ValueKey& key) -> bool {
return key.opcode() == Const32 || key.opcode() == Const64 || key.opcode() == ArgumentReg;
});
}
private:
template<typename Filter>
void hoistConstants(const Filter& filter)
{
Dominators& dominators = m_proc.dominators();
HashMap<ValueKey, Value*> valueForConstant;
IndexMap<BasicBlock*, Vector<Value*>> materializations(m_proc.size());
// We determine where things get materialized based on where they are used.
for (BasicBlock* block : m_proc) {
for (Value* value : *block) {
for (Value*& child : value->children()) {
ValueKey key = child->key();
if (!filter(key))
continue;
auto result = valueForConstant.add(key, child);
if (result.isNewEntry) {
// Assume that this block is where we want to materialize the value.
child->owner = block;
continue;
}
// Make 'value' use the canonical constant rather than the one it was using.
child = result.iterator->value;
// Determine the least common dominator. That's the lowest place in the CFG where
// we could materialize the constant while still having only one materialization
// in the resulting code.
while (!dominators.dominates(child->owner, block))
child->owner = dominators.idom(child->owner);
}
}
}
// Make sure that each basic block knows what to materialize. This also refines the
// materialization block based on execution frequency. It finds the minimum block frequency
// of all of its dominators, and selects the closest block amongst those that are tied for
// lowest frequency.
for (auto& entry : valueForConstant) {
Value* value = entry.value;
for (BasicBlock* block = value->owner; block; block = dominators.idom(block)) {
if (block->frequency() < value->owner->frequency())
value->owner = block;
}
materializations[value->owner].append(value);
}
// Get rid of Value's that are fast constants but aren't canonical. Also remove the canonical
// ones from the CFG, since we're going to reinsert them elsewhere.
for (BasicBlock* block : m_proc) {
for (Value*& value : *block) {
ValueKey key = value->key();
if (!filter(key))
continue;
if (valueForConstant.get(key) == value)
value = m_proc.add<Value>(Nop, value->origin());
else
value->replaceWithNopIgnoringType();
}
}
// Now make sure that we move constants to where they are supposed to go. Again, we do this
// based on uses.
for (BasicBlock* block : m_proc) {
for (unsigned valueIndex = 0; valueIndex < block->size(); ++valueIndex) {
Value* value = block->at(valueIndex);
// This finds the outermost (best) block last. So, the functor overrides the result
// each time it finds something acceptable.
auto findBestConstant = [&] (const auto& predicate) -> Value* {
Value* result = nullptr;
dominators.forAllDominatorsOf(
block,
[&] (BasicBlock* dominator) {
for (Value* value : materializations[dominator]) {
if (predicate(value)) {
result = value;
break;
}
}
});
return result;
};
// We call this when we have found a constant that we'd like to use. It's possible that
// we have computed that the constant should be meterialized in this block, but we
// haven't inserted it yet. This inserts the constant if necessary.
auto materialize = [&] (Value* child) {
ValueKey key = child->key();
if (!filter(key))
return;
// If we encounter a fast constant, then it must be canonical, since we already
// got rid of the non-canonical ones.
ASSERT(valueForConstant.get(key) == child);
if (child->owner != block) {
// This constant isn't our problem. It's going to be materialized in another
// block.
return;
}
// We're supposed to materialize this constant in this block, and we haven't
// done it yet.
m_insertionSet.insertValue(valueIndex, child);
child->owner = nullptr;
};
if (MemoryValue* memoryValue = value->as<MemoryValue>()) {
Value* pointer = memoryValue->lastChild();
if (pointer->hasIntPtr() && filter(pointer->key())) {
auto desiredOffset = [&] (Value* otherPointer) -> intptr_t {
// We would turn this:
//
// Load(@p, offset = c)
//
// into this:
//
// Load(@q, offset = ?)
//
// The offset should be c + @p - @q, because then we're loading from:
//
// @q + c + @p - @q
uintptr_t c = static_cast<uintptr_t>(static_cast<intptr_t>(memoryValue->offset()));
uintptr_t p = pointer->asIntPtr();
uintptr_t q = otherPointer->asIntPtr();
return c + p - q;
};
Value* bestPointer = findBestConstant(
[&] (Value* candidatePointer) -> bool {
if (!candidatePointer->hasIntPtr())
return false;
int64_t offset = desiredOffset(candidatePointer);
return memoryValue->isLegalOffset(offset);
});
if (bestPointer) {
memoryValue->lastChild() = bestPointer;
memoryValue->setOffset(static_cast<int32_t>(desiredOffset(bestPointer)));
}
}
} else {
switch (value->opcode()) {
case Add:
case Sub: {
Value* addend = value->child(1);
if (!addend->hasInt() || !filter(addend->key()))
break;
int64_t addendConst = addend->asInt();
Value* bestAddend = findBestConstant(
[&] (Value* candidateAddend) -> bool {
if (candidateAddend->type() != addend->type())
return false;
if (!candidateAddend->hasInt())
return false;
return candidateAddend == addend
|| candidateAddend->asInt() == -addendConst;
});
if (!bestAddend || bestAddend == addend)
break;
materialize(value->child(0));
materialize(bestAddend);
value->replaceWithIdentity(
m_insertionSet.insert<Value>(
valueIndex, value->opcode() == Add ? Sub : Add, value->origin(),
value->child(0), bestAddend));
break;
}
default:
break;
}
}
for (Value* child : value->children())
materialize(child);
}
// We may have some constants that need to be materialized right at the end of this
// block.
for (Value* value : materializations[block]) {
if (!value->owner) {
// It's already materialized in this block.
continue;
}
m_insertionSet.insertValue(block->size() - 1, value);
}
m_insertionSet.execute(block);
}
}
void lowerFPConstants()
{
for (Value* value : m_proc.values()) {
ValueKey key = value->key();
if (goesInTable(key))
m_constTable.add(key, m_constTable.size());
}
m_dataSection = static_cast<int64_t*>(m_proc.addDataSection(m_constTable.size() * sizeof(int64_t)));
for (auto& entry : m_constTable)
m_dataSection[entry.value] = entry.key.value();
IndexSet<Value*> offLimits;
for (BasicBlock* block : m_proc) {
for (unsigned valueIndex = 0; valueIndex < block->size(); ++valueIndex) {
StackmapValue* value = block->at(valueIndex)->as<StackmapValue>();
if (!value)
continue;
for (unsigned childIndex = 0; childIndex < value->numChildren(); ++childIndex) {
if (!value->constrainedChild(childIndex).rep().isAny())
continue;
Value*& child = value->child(childIndex);
ValueKey key = child->key();
if (!goesInTable(key))
continue;
child = m_insertionSet.insertValue(
valueIndex, key.materialize(m_proc, value->origin()));
offLimits.add(child);
}
}
m_insertionSet.execute(block);
}
for (BasicBlock* block : m_proc) {
for (unsigned valueIndex = 0; valueIndex < block->size(); ++valueIndex) {
Value* value = block->at(valueIndex);
ValueKey key = value->key();
if (!goesInTable(key))
continue;
if (offLimits.contains(value))
continue;
auto offset = sizeof(int64_t) * m_constTable.get(key);
if (!isRepresentableAs<Value::OffsetType>(offset))
continue;
Value* tableBase = m_insertionSet.insertIntConstant(
valueIndex, value->origin(), pointerType(),
bitwise_cast<intptr_t>(m_dataSection));
Value* result = m_insertionSet.insert<MemoryValue>(
valueIndex, Load, value->type(), value->origin(), tableBase,
static_cast<Value::OffsetType>(offset));
value->replaceWithIdentity(result);
}
m_insertionSet.execute(block);
}
}
bool goesInTable(const ValueKey& key)
{
return (key.opcode() == ConstDouble && key != doubleZero())
|| (key.opcode() == ConstFloat && key != floatZero());
}
static ValueKey doubleZero()
{
return ValueKey(ConstDouble, Double, 0.0);
}
static ValueKey floatZero()
{
return ValueKey(ConstFloat, Float, 0.0);
}
Procedure& m_proc;
HashMap<ValueKey, unsigned> m_constTable;
int64_t* m_dataSection;
InsertionSet m_insertionSet;
};
} // anonymous namespace
void moveConstants(Procedure& proc)
{
PhaseScope phaseScope(proc, "moveConstants");
MoveConstants moveConstants(proc);
moveConstants.run();
}
} } // namespace JSC::B3
#endif // ENABLE(B3_JIT)