| /* |
| * Copyright (C) 2019-2020 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 "B3ReduceLoopStrength.h" |
| |
| #if ENABLE(B3_JIT) |
| |
| #include "B3BasicBlockInlines.h" |
| #include "B3BlockInsertionSet.h" |
| #include "B3ConstPtrValue.h" |
| #include "B3InsertionSet.h" |
| #include "B3NaturalLoops.h" |
| #include "B3PhaseScope.h" |
| #include "B3ProcedureInlines.h" |
| #include "B3ValueInlines.h" |
| #include <wtf/SmallPtrSet.h> |
| #include <wtf/Vector.h> |
| |
| namespace JSC { namespace B3 { |
| |
| #if CPU(X86_64) |
| /* |
| * The semantics of B3 require that loads and stores are not reduced in granularity. |
| * If we would use system memcpy, then it is possible that we would get a byte copy loop, |
| * and this could cause GC tearing. |
| */ |
| void fastForwardCopy32(uint32_t* dst, const uint32_t* src, size_t size) |
| { |
| uint64_t i; |
| int64_t counter; |
| uint64_t tmp, tmp2; |
| |
| asm volatile( |
| "test %q[size], %q[size]\t\n" |
| "jz 900f\t\n" // exit |
| "xorq %q[i], %q[i]\t\n" |
| // if size < 8 |
| "cmp $8, %q[size]\t\n" |
| "jl 100f\t\n" // backporch |
| // if (dst + size*4 <= src || src + size*4 <= dst) |
| "leaq (%q[src], %q[size], 4), %q[tmp]\t\n" |
| "cmp %q[tmp], %q[dst]\t\n" |
| "jae 500f\t\n" // simd no overlap |
| "leaq (%q[dst], %q[size], 4), %q[tmp]\t\n" |
| "cmp %q[tmp], %q[src]\t\n" |
| "jae 500f\t\n" // simd no overlap |
| "jmp 100f\t\n" // Backporch |
| |
| // Backporch (assumes we can write at least one int) |
| "100:\t\n" |
| // counter = (size - i)%4 |
| "mov %q[size], %q[counter]\t\n" |
| "subq %q[i], %q[counter]\t\n" |
| |
| // If we are a multiple of 4, unroll the loop |
| // We already know we are nonzero |
| "and $3, %q[counter]\t\n" |
| "jz 200f\t\n" // unrolled loop |
| |
| "negq %q[counter]\t\n" |
| ".balign 32\t\n" |
| "101:\t\n" |
| "mov (%q[src], %q[i], 4), %k[tmp]\t\n" |
| "mov %k[tmp], (%q[dst], %q[i], 4)\t\n" |
| "incq %q[i]\t\n" |
| "incq %q[counter]\t\n" |
| "jnz 101b\t\n" |
| // Do we still have anything left? |
| "cmpq %q[size], %q[i]\t\n" |
| "je 900f\t\n" // exit |
| // Then go to the unrolled loop |
| "jmp 200f\t\n" |
| |
| // Unrolled loop (assumes multiple of 4, can do one iteration) |
| "200:\t\n" |
| "shr $2, %q[counter]\t\n" |
| "negq %q[counter]\t\n" |
| ".balign 32\t\n" |
| "201:\t\n" |
| "mov (%q[src], %q[i], 4), %k[tmp]\t\n" |
| "mov %k[tmp], (%q[dst], %q[i], 4)\t\n" |
| "mov 4(%q[src], %q[i], 4), %k[tmp2]\t\n" |
| "mov %k[tmp2], 4(%q[dst], %q[i], 4)\t\n" |
| "mov 8(%q[src], %q[i], 4), %k[tmp2]\t\n" |
| "mov %k[tmp2], 8(%q[dst], %q[i], 4)\t\n" |
| "mov 12(%q[src], %q[i], 4), %k[tmp]\t\n" |
| "mov %k[tmp], 12(%q[dst], %q[i], 4)\t\n" |
| "addq $4, %q[i]\t\n" |
| "cmpq %q[size], %q[i]\t\n" |
| "jb 201b\t\n" |
| "jmp 900f\t\n" // exit |
| |
| // simd no overlap |
| // counter = -(size/8); |
| "500:\t\n" |
| "mov %q[size], %q[counter]\t\n" |
| "shrq $3, %q[counter]\t\n" |
| "negq %q[counter]\t\n" |
| ".balign 32\t\n" |
| "501:\t\n" |
| "movups (%q[src], %q[i], 4), %%xmm0\t\n" |
| "movups 16(%q[src], %q[i], 4), %%xmm1\t\n" |
| "movups %%xmm0, (%q[dst], %q[i], 4)\t\n" |
| "movups %%xmm1, 16(%q[dst], %q[i], 4)\t\n" |
| "addq $8, %q[i]\t\n" |
| "incq %q[counter]\t\n" |
| "jnz 501b\t\n" |
| // if (i == size) |
| "cmpq %q[size], %q[i]\t\n" |
| "je 900f\t\n" // end |
| "jmp 100b\t\n" // backporch |
| "900:\t\n" |
| : [i] "=&c" (i), [counter] "=&r" (counter), [tmp] "=&a" (tmp), [tmp2] "=&r" (tmp2) |
| : [dst] "D" (dst), [src] "S" (src), [size] "r" (size) |
| : "xmm0", "xmm1"); |
| } |
| #endif |
| |
| class ReduceLoopStrength { |
| static constexpr bool verbose = false; |
| |
| struct AddrInfo { |
| Value* appendAddr(Procedure& proc, BasicBlock* block, Value* addr) |
| { |
| block->appendNew<Value>(proc, Identity, addr->origin(), addr); |
| return addr; |
| } |
| |
| Value* insideLoopAddr; |
| |
| Value* arrayBase; |
| Value* index; |
| }; |
| |
| public: |
| ReduceLoopStrength(Procedure& proc) |
| : m_proc(proc) |
| , m_insertionSet(proc) |
| , m_blockInsertionSet(proc) |
| , m_root(proc.at(0)) |
| , m_phiChildren(proc) |
| { |
| } |
| |
| #if CPU(X86_64) |
| void reduceByteCopyLoopsToMemcpy() |
| { |
| HashSet<Value*> patternMatchedValues; |
| |
| Value* store = m_value; |
| if (store->opcode() != Store) |
| return; |
| patternMatchedValues.add(store); |
| |
| Value* load = store->child(0); |
| uint32_t elemSize = sizeofType(load->type()); |
| if (load->opcode() != Load || elemSize != 4) |
| return; |
| patternMatchedValues.add(load); |
| |
| if (verbose) |
| dataLogLn("Found store/load:", *store); |
| |
| auto extractArrayInfo = [&] (Value* value) -> Optional<AddrInfo> { |
| patternMatchedValues.add(value); |
| |
| Optional<AddrInfo> addr = { AddrInfo() }; |
| |
| Value* sum = value; |
| if (value->opcode() == ZExt32) |
| sum = sum->child(0); |
| |
| if (sum->opcode() != Add || sum->numChildren() != 2) |
| return { }; |
| |
| addr->insideLoopAddr = sum; |
| auto extractLoopIndexInSubtree = [&] (Value* value) -> Value* { |
| // Match arrBase[i*elemSize] |
| if (value->opcode() == Shl |
| && value->child(0)->opcode() == Phi |
| && value->child(1)->isInt(WTF::fastLog2(elemSize))) |
| return value->child(0); |
| if (value->opcode() == Shl |
| && value->child(0)->opcode() == ZExt32 |
| && value->child(0)->child(0)->opcode() == Phi |
| && value->child(1)->isInt(WTF::fastLog2(elemSize))) |
| return value->child(0)->child(0); |
| return nullptr; |
| }; |
| |
| // Try to find a known pattern applied to a single phi, which we can assume is our loop index. |
| Value* left = extractLoopIndexInSubtree(sum->child(0)); |
| Value* right = extractLoopIndexInSubtree(sum->child(1)); |
| if (left && !right) { |
| addr->index = left; |
| addr->arrayBase = sum->child(1); |
| } else if (right && !left) { |
| addr->index = right; |
| addr->arrayBase = sum->child(0); |
| } else |
| return { }; |
| |
| patternMatchedValues.add(addr->index); |
| patternMatchedValues.add(addr->arrayBase); |
| |
| return addr; |
| }; |
| |
| auto destination = extractArrayInfo(store->child(1)); |
| auto source = extractArrayInfo(load->child(0)); |
| |
| if (!source || !destination || source->index != destination->index) |
| return; |
| |
| if (destination->arrayBase->type() != Int64 || source->arrayBase->type() != Int64) |
| return; |
| |
| if (verbose) |
| dataLogLn("Found array info: ", *source->arrayBase, "[", *source->index, "] = ", *destination->arrayBase, "[", *destination->index, "]"); |
| |
| // Find the loop header, footer and inner blocks. |
| // Verify that there is one entrance to and one exit from the loop. |
| auto* loop = m_proc.naturalLoops().innerMostLoopOf(m_block); |
| if (!loop) |
| return; |
| BasicBlock* loopHead = loop->header(); |
| BasicBlock* loopFoot = nullptr; |
| BasicBlock* loopPreheader = nullptr; |
| BasicBlock* loopPostfooter = nullptr; |
| SmallPtrSet<BasicBlock*> loopInnerBlocks; |
| |
| { |
| for (unsigned i = 0; i < loop->size(); ++i) |
| loopInnerBlocks.add(loop->at(i)); |
| |
| if (!loopInnerBlocks.contains(load->owner)) |
| return; |
| |
| if (!loopInnerBlocks.contains(store->owner)) |
| return; |
| |
| SmallPtrSet<BasicBlock*> loopEntrances; |
| SmallPtrSet<BasicBlock*> loopExits; |
| for (auto* block : loopInnerBlocks) { |
| for (auto successor : block->successors()) { |
| if (!loopInnerBlocks.contains(successor.block())) |
| loopExits.add(successor.block()); |
| } |
| for (auto* predecessor : block->predecessors()) { |
| if (!loopInnerBlocks.contains(predecessor)) |
| loopEntrances.add(predecessor); |
| } |
| } |
| |
| if (loopExits.size() != 1) { |
| if (verbose) { |
| dataLog("Loop has incorrect number of exits: "); |
| for (BasicBlock* block : loopExits) |
| dataLog(*block, " "); |
| dataLogLn(); |
| } |
| return; |
| } |
| loopPostfooter = *loopExits.begin(); |
| |
| if (loopEntrances.size() != 1) { |
| if (verbose) { |
| dataLog("Loop has incorrect number of entrances: "); |
| for (BasicBlock* block : loopEntrances) |
| dataLog(*block, " "); |
| dataLogLn(); |
| } |
| return; |
| } |
| loopPreheader = *loopEntrances.begin(); |
| |
| if (!loopHead->predecessors().contains(loopPreheader)) { |
| if (verbose) |
| dataLogLn("Loop head does not follow preheader"); |
| return; |
| } |
| |
| for (BasicBlock* predecessor : loopPostfooter->predecessors()) { |
| if (loopInnerBlocks.contains(predecessor)) { |
| // There is only one loop exit. |
| RELEASE_ASSERT(!loopFoot); |
| loopFoot = predecessor; |
| } |
| } |
| } |
| |
| if (verbose) { |
| dataLog("Found loop head:", *loopHead, " foot:", *loopFoot, " prehead ", *loopPreheader, " postfoot ", *loopPostfooter, " inner blocks: "); |
| for (BasicBlock* block : loopInnerBlocks) |
| dataLog(*block, " "); |
| dataLogLn(); |
| } |
| |
| // Verify that the index is a monotonic inductive variable. |
| Value* startingIndex = nullptr; |
| { |
| if (m_phiChildren.at(source->index).size() != 2) |
| return; |
| |
| Value* updateIndex = nullptr; |
| for (Value* up : m_phiChildren.at(source->index)) { |
| if (m_proc.dominators().dominates(up->owner, loopPreheader)) |
| startingIndex = up; |
| else |
| updateIndex = up; |
| } |
| |
| if (!updateIndex || !startingIndex || !loopInnerBlocks.contains(updateIndex->owner)) |
| return; |
| patternMatchedValues.add(updateIndex); |
| patternMatchedValues.add(startingIndex); |
| |
| updateIndex = updateIndex->child(0); |
| startingIndex = startingIndex->child(0); |
| if (updateIndex->opcode() != Add || !updateIndex->child(1)->isInt(1) || updateIndex->child(0) != source->index) |
| return; |
| |
| if (!startingIndex->isInt(0)) |
| return; |
| } |
| |
| if (verbose) |
| dataLogLn("Found starting index:", *startingIndex); |
| |
| // Identify the loop exit condition. |
| Value* exitCondition = nullptr; |
| // Is this an exit condition or a continuation condition? |
| bool conditionInverted = false; |
| // Do we check the index before or after using it? |
| bool checkBeforeWrite = false; |
| { |
| Value* branch = loopFoot->last(); |
| if (branch->opcode() != Branch) |
| return; |
| patternMatchedValues.add(branch); |
| exitCondition = branch->child(0); |
| |
| conditionInverted = loopPostfooter != loopFoot->successor(0).block(); |
| checkBeforeWrite = m_proc.dominators().strictlyDominates(loopFoot, m_block); |
| } |
| |
| if (verbose) |
| dataLogLn("Found exit condition: ", *exitCondition, " inverted: ", conditionInverted, " checks before the first write: ", checkBeforeWrite); |
| |
| // Idenfity the loop bound by matching loop bound expressions. |
| Value* loopBound = nullptr; |
| { |
| auto extractLoopBound = [&] (Value* index, Value* bound) -> Value* { |
| // Match i+1 when we do a write first followed by the check for the next iteration |
| if (!checkBeforeWrite && index->opcode() == Add && index->child(0) == source->index && index->child(1)->isInt(1)) |
| return bound; |
| return nullptr; |
| }; |
| |
| if (exitCondition->opcode() == GreaterThan && conditionInverted) { |
| // enter loop again if size > i |
| loopBound = extractLoopBound(exitCondition->child(1), exitCondition->child(0)); |
| } else if (exitCondition->opcode() == LessThan && !conditionInverted) { |
| // enter loop again if size < i |
| loopBound = extractLoopBound(exitCondition->child(1), exitCondition->child(0)); |
| } |
| |
| if (!loopBound) { |
| if (verbose) |
| dataLogLn("Unable to extract bound from exit condition ", *exitCondition); |
| return; |
| } |
| } |
| |
| // Make sure there are no other effectful things happening. |
| // This also guarantees that we found the only branch in the loop. This means that our |
| // load/store must happen iff our index update and branch do. |
| for (BasicBlock* block : loopInnerBlocks) { |
| for (unsigned index = 0; index < block->size(); ++index) { |
| Value* value = block->at(index); |
| if (patternMatchedValues.contains(value) || value->opcode() == Jump) |
| continue; |
| |
| Effects effects = value->effects(); |
| effects.readsLocalState = false; |
| if (effects != Effects::none()) { |
| if (verbose) |
| dataLogLn("Not byte copy loop, node ", *value, " has effects"); |
| return; |
| } |
| } |
| } |
| |
| if (!hoistValue(loopPreheader, source->arrayBase, false) |
| || !hoistValue(loopPreheader, destination->arrayBase, false) |
| || !hoistValue(loopPreheader, loopBound, false)) |
| return; |
| |
| if (verbose) |
| dataLogLn("Found byte copy loop: ", *source->arrayBase, "[", *source->index, "] = ", *destination->arrayBase, "[", *destination->index, "] from index ", *startingIndex, " to max index ", *loopBound, " stride: ", elemSize); |
| |
| bool hoistResult = hoistValue(loopPreheader, source->arrayBase); |
| hoistResult &= hoistValue(loopPreheader, destination->arrayBase); |
| hoistResult &= hoistValue(loopPreheader, loopBound); |
| ASSERT_UNUSED(hoistResult, hoistResult); |
| |
| auto origin = loopPostfooter->at(0)->origin(); |
| |
| BasicBlock* memcpy = m_blockInsertionSet.insertBefore(loopPostfooter, loopPostfooter->frequency()); |
| memcpy->setSuccessors(FrequentedBlock(loopPostfooter)); |
| memcpy->addPredecessor(loopPreheader); |
| while (loopPostfooter->predecessors().size()) |
| loopPostfooter->removePredecessor(loopPostfooter->predecessors()[0]); |
| loopPostfooter->addPredecessor(memcpy); |
| loopPreheader->setSuccessors(memcpy); |
| |
| Effects effects = Effects::forCall(); |
| memcpy->appendNew<CCallValue>(m_proc, B3::Void, origin, effects, |
| memcpy->appendNew<ConstPtrValue>(m_proc, origin, tagCFunction<B3CCallPtrTag>(fastForwardCopy32)), |
| destination->appendAddr(m_proc, memcpy, destination->arrayBase), |
| source->appendAddr(m_proc, memcpy, source->arrayBase), |
| loopBound); |
| |
| memcpy->appendNew<Value>(m_proc, Jump, origin); |
| } |
| |
| bool hoistValue(BasicBlock* into, Value* value, bool canMutate = true) |
| { |
| if (m_proc.dominators().dominates(value->owner, into)) |
| return true; |
| |
| Effects effects = value->effects(); |
| if (effects != Effects::none()) { |
| if (verbose) |
| dataLogLn("Cannot hoist ", *value, " into ", *into, " since it has effects"); |
| return false; |
| } |
| |
| for (Value* child : value->children()) { |
| if (!hoistValue(into, child, false)) |
| return false; |
| } |
| |
| if (canMutate) { |
| for (Value* child : value->children()) |
| hoistValue(into, child); |
| |
| value->owner->at(value->index()) = m_proc.add<Value>(Nop, Void, value->origin()); |
| into->appendNonTerminal(value); |
| } |
| |
| return true; |
| } |
| |
| bool run() |
| { |
| if (verbose) |
| dataLogLn("ReduceLoopStrength examining proc: ", m_proc); |
| bool result = false; |
| |
| do { |
| m_changed = false; |
| |
| for (BasicBlock* block : m_proc.blocksInPreOrder()) { |
| m_block = block; |
| |
| for (m_index = 0; m_index < block->size(); ++m_index) { |
| m_value = m_block->at(m_index); |
| m_value->performSubstitution(); |
| reduceByteCopyLoopsToMemcpy(); |
| m_insertionSet.execute(m_block); |
| m_changed |= m_blockInsertionSet.execute(); |
| |
| if (m_changed) { |
| m_proc.resetReachability(); |
| m_proc.invalidateCFG(); |
| m_proc.resetValueOwners(); |
| result = true; |
| break; |
| } |
| } |
| |
| if (m_changed) |
| break; |
| } |
| } while (m_changed && m_proc.optLevel() >= 2); |
| |
| if (result && verbose) |
| dataLogLn("ReduceLoopStrength produced proc: ", m_proc); |
| |
| return result; |
| } |
| #else |
| bool run() |
| { |
| return false; |
| } |
| #endif |
| |
| Procedure& m_proc; |
| InsertionSet m_insertionSet; |
| BlockInsertionSet m_blockInsertionSet; |
| BasicBlock* m_root { nullptr }; |
| BasicBlock* m_block { nullptr }; |
| unsigned m_index { 0 }; |
| Value* m_value { nullptr }; |
| bool m_changed { false }; |
| PhiChildren m_phiChildren; |
| }; |
| |
| bool reduceLoopStrength(Procedure& proc) |
| { |
| PhaseScope phaseScope(proc, "reduceLoopStrength"); |
| return ReduceLoopStrength(proc).run(); |
| } |
| |
| } } // namespace JSC::B3 |
| |
| #endif // ENABLE(B3_JIT) |
