Add m-esr52 at 52.6.0

1 files changed, 190 insertions, 0 deletions

diff --git a/js/src/jit/InstructionReordering.cpp b/js/src/jit/InstructionReordering.cpp
new file mode 100644
index 000000000..48b619b7c
--- /dev/null
+++ b/js/src/jit/InstructionReordering.cpp
@@ -0,0 +1,190 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "jit/InstructionReordering.h"
+#include "jit/MIRGraph.h"
+
+using namespace js;
+using namespace js::jit;
+
+static void
+MoveBefore(MBasicBlock* block, MInstruction* at, MInstruction* ins)
+{
+    if (at == ins)
+        return;
+
+    // Update instruction numbers.
+    for (MInstructionIterator iter(block->begin(at)); *iter != ins; iter++) {
+        MOZ_ASSERT(iter->id() < ins->id());
+        iter->setId(iter->id() + 1);
+    }
+    ins->setId(at->id() - 1);
+    block->moveBefore(at, ins);
+}
+
+static bool
+IsLastUse(MDefinition* ins, MDefinition* input, MBasicBlock* loopHeader)
+{
+    // If we are in a loop, this cannot be the last use of any definitions from
+    // outside the loop, as those definitions can be used in future iterations.
+    if (loopHeader && input->block()->id() < loopHeader->id())
+        return false;
+    for (MUseDefIterator iter(input); iter; iter++) {
+        // Watch for uses defined in blocks which ReorderInstructions hasn't
+        // processed yet. These nodes have not had their ids set yet.
+        if (iter.def()->block()->id() > ins->block()->id())
+            return false;
+        if (iter.def()->id() > ins->id())
+            return false;
+    }
+    return true;
+}
+
+bool
+jit::ReorderInstructions(MIRGenerator* mir, MIRGraph& graph)
+{
+    // Renumber all instructions in the graph as we go.
+    size_t nextId = 0;
+
+    // List of the headers of any loops we are in.
+    Vector<MBasicBlock*, 4, SystemAllocPolicy> loopHeaders;
+
+    for (ReversePostorderIterator block(graph.rpoBegin()); block != graph.rpoEnd(); block++) {
+        // Renumber all definitions inside the basic blocks.
+        for (MPhiIterator iter(block->phisBegin()); iter != block->phisEnd(); iter++)
+            iter->setId(nextId++);
+
+        for (MInstructionIterator iter(block->begin()); iter != block->end(); iter++)
+            iter->setId(nextId++);
+
+        // Don't reorder instructions within entry blocks, which have special requirements.
+        if (*block == graph.entryBlock() || *block == graph.osrBlock())
+            continue;
+
+        if (block->isLoopHeader()) {
+            if (!loopHeaders.append(*block))
+                return false;
+        }
+
+        MBasicBlock* innerLoop = loopHeaders.empty() ? nullptr : loopHeaders.back();
+
+        MInstruction* top = block->safeInsertTop();
+        MInstructionReverseIterator rtop = ++block->rbegin(top);
+        for (MInstructionIterator iter(block->begin(top)); iter != block->end(); ) {
+            MInstruction* ins = *iter;
+
+            // Filter out some instructions which are never reordered.
+            if (ins->isEffectful() ||
+                !ins->isMovable() ||
+                ins->resumePoint() ||
+                ins == block->lastIns())
+            {
+                iter++;
+                continue;
+            }
+
+            // Move constants with a single use in the current block to the
+            // start of the block. Constants won't be reordered by the logic
+            // below, as they have no inputs. Moving them up as high as
+            // possible can allow their use to be moved up further, though,
+            // and has no cost if the constant is emitted at its use.
+            if (ins->isConstant() &&
+                ins->hasOneUse() &&
+                ins->usesBegin()->consumer()->block() == *block &&
+                !IsFloatingPointType(ins->type()))
+            {
+                iter++;
+                MInstructionIterator targetIter = block->begin();
+                while (targetIter->isConstant() || targetIter->isInterruptCheck()) {
+                    if (*targetIter == ins)
+                        break;
+                    targetIter++;
+                }
+                MoveBefore(*block, *targetIter, ins);
+                continue;
+            }
+
+            // Look for inputs where this instruction is the last use of that
+            // input. If we move this instruction up, the input's lifetime will
+            // be shortened, modulo resume point uses (which don't need to be
+            // stored in a register, and can be handled by the register
+            // allocator by just spilling at some point with no reload).
+            Vector<MDefinition*, 4, SystemAllocPolicy> lastUsedInputs;
+            for (size_t i = 0; i < ins->numOperands(); i++) {
+                MDefinition* input = ins->getOperand(i);
+                if (!input->isConstant() && IsLastUse(ins, input, innerLoop)) {
+                    if (!lastUsedInputs.append(input))
+                        return false;
+                }
+            }
+
+            // Don't try to move instructions which aren't the last use of any
+            // of their inputs (we really ought to move these down instead).
+            if (lastUsedInputs.length() < 2) {
+                iter++;
+                continue;
+            }
+
+            MInstruction* target = ins;
+            for (MInstructionReverseIterator riter = ++block->rbegin(ins); riter != rtop; riter++) {
+                MInstruction* prev = *riter;
+                if (prev->isInterruptCheck())
+                    break;
+
+                // The instruction can't be moved before any of its uses.
+                bool isUse = false;
+                for (size_t i = 0; i < ins->numOperands(); i++) {
+                    if (ins->getOperand(i) == prev) {
+                        isUse = true;
+                        break;
+                    }
+                }
+                if (isUse)
+                    break;
+
+                // The instruction can't be moved before an instruction that
+                // stores to a location read by the instruction.
+                if (prev->isEffectful() &&
+                    (ins->getAliasSet().flags() & prev->getAliasSet().flags()) &&
+                    ins->mightAlias(prev) != MDefinition::AliasType::NoAlias)
+                {
+                    break;
+                }
+
+                // Make sure the instruction will still be the last use of one
+                // of its inputs when moved up this far.
+                for (size_t i = 0; i < lastUsedInputs.length(); ) {
+                    bool found = false;
+                    for (size_t j = 0; j < prev->numOperands(); j++) {
+                        if (prev->getOperand(j) == lastUsedInputs[i]) {
+                            found = true;
+                            break;
+                        }
+                    }
+                    if (found) {
+                        lastUsedInputs[i] = lastUsedInputs.back();
+                        lastUsedInputs.popBack();
+                    } else {
+                        i++;
+                    }
+                }
+                if (lastUsedInputs.length() < 2)
+                    break;
+
+                // We can move the instruction before this one.
+                target = prev;
+            }
+
+            iter++;
+            MoveBefore(*block, target, ins);
+        }
+
+        if (block->isLoopBackedge())
+            loopHeaders.popBack();
+    }
+
+    return true;
+}