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-rw-r--r--src/cfg/cfg-traversal.h313
-rw-r--r--src/passes/CMakeLists.txt1
-rw-r--r--src/passes/CoalesceLocals.cpp353
-rw-r--r--src/passes/pass.cpp1
-rw-r--r--src/tools/wasm-as.cpp2
5 files changed, 669 insertions, 1 deletions
diff --git a/src/cfg/cfg-traversal.h b/src/cfg/cfg-traversal.h
new file mode 100644
index 000000000..f6c055542
--- /dev/null
+++ b/src/cfg/cfg-traversal.h
@@ -0,0 +1,313 @@
+/*
+ * Copyright 2016 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Convert the AST to a CFG, while traversing it.
+//
+// Note that this is not the same as the relooper CFG. The relooper is
+// designed for compilation to an AST, this is for processing. There is
+// no built-in support for transforming this CFG into the AST back
+// again, it is just metadata on the side for computation purposes.
+//
+// Usage: As the traversal proceeds, you can note information and add it to
+// the current basic block using currBasicBlock, on the contents
+// property, whose type is user-defined.
+//
+
+#ifndef cfg_traversal_h
+#define cfg_traversal_h
+
+#include "wasm.h"
+#include "wasm-traversal.h"
+
+namespace wasm {
+
+template<typename SubType, typename VisitorType, typename Contents>
+struct CFGWalker : public PostWalker<SubType, VisitorType> {
+
+ // public interface
+
+ struct BasicBlock {
+ Contents contents; // custom contents
+ std::vector<BasicBlock*> out, in;
+ };
+
+ BasicBlock* entry; // the entry block
+
+ BasicBlock* makeBasicBlock() { // override this with code to create a BasicBlock if necessary
+ return new BasicBlock();
+ }
+
+ // internal details
+
+ std::vector<std::unique_ptr<BasicBlock>> basicBlocks; // all the blocks
+
+ // traversal state
+ BasicBlock* currBasicBlock; // the current block in play during traversal
+ std::map<Name, std::vector<BasicBlock*>> branches;
+ std::vector<BasicBlock*> ifStack;
+ std::vector<BasicBlock*> loopStack;
+
+ static void doStartBasicBlock(SubType* self, Expression** currp) {
+ self->currBasicBlock = self->makeBasicBlock();
+ self->basicBlocks.push_back(std::unique_ptr<BasicBlock>(self->currBasicBlock));
+ }
+
+ void link(BasicBlock* from, BasicBlock* to) {
+ from->out.push_back(to);
+ to->in.push_back(from);
+ }
+
+ static void doEndBlock(SubType* self, Expression** currp) {
+ // TODO: if no name, no need for a new block
+ auto* last = self->currBasicBlock;
+ doStartBasicBlock(self, currp);
+ self->link(last, self->currBasicBlock); // fallthrough
+ // branches to the new one
+ auto* curr = (*currp)->cast<Block>();
+ if (curr->name.is()) {
+ auto& origins = self->branches[curr->name];
+ for (auto* origin : origins) {
+ self->link(origin, self->currBasicBlock);
+ }
+ self->branches.erase(curr->name);
+ }
+ }
+
+ static void doStartIfTrue(SubType* self, Expression** currp) {
+ auto* last = self->currBasicBlock;
+ doStartBasicBlock(self, currp);
+ self->link(last, self->currBasicBlock); // ifTrue
+ self->ifStack.push_back(last); // the block before the ifTrue
+ }
+
+ static void doStartIfFalse(SubType* self, Expression** currp) {
+ self->ifStack.push_back(self->currBasicBlock); // the ifTrue fallthrough
+ doStartBasicBlock(self, currp);
+ self->link(self->ifStack[self->ifStack.size() - 2], self->currBasicBlock); // before if -> ifFalse
+ }
+
+ static void doEndIf(SubType* self, Expression** currp) {
+ auto* last = self->currBasicBlock;
+ doStartBasicBlock(self, currp);
+ self->link(last, self->currBasicBlock); // last one is ifFalse's fallthrough if there was one, otherwise it's the ifTrue fallthrough
+ if ((*currp)->cast<If>()->ifFalse) {
+ // we just linked ifFalse, need to link ifTrue to the end
+ self->link(self->ifStack.back(), self->currBasicBlock);
+ self->ifStack.pop_back();
+ } else {
+ // no ifFalse, so add a fallthrough for if the if is not taken
+ self->link(self->ifStack.back(), self->currBasicBlock);
+ }
+ self->ifStack.pop_back();
+ }
+
+ static void doStartLoop(SubType* self, Expression** currp) {
+ auto* last = self->currBasicBlock;
+ doStartBasicBlock(self, currp);
+ self->link(last, self->currBasicBlock);
+ self->loopStack.push_back(self->currBasicBlock);
+ }
+
+ static void doEndLoop(SubType* self, Expression** currp) {
+ auto* last = self->currBasicBlock;
+ doStartBasicBlock(self, currp);
+ self->link(last, self->currBasicBlock); // fallthrough
+ // branches to the new one
+ auto* curr = (*currp)->cast<Loop>();
+ if (curr->out.is()) {
+ auto& origins = self->branches[curr->out];
+ for (auto* origin : origins) {
+ self->link(origin, self->currBasicBlock);
+ }
+ self->branches.erase(curr->out);
+ }
+ // branches to the top of the loop
+ if (curr->in.is()) {
+ auto* loopStart = self->loopStack.back();
+ auto& origins = self->branches[curr->in];
+ for (auto* origin : origins) {
+ self->link(origin, loopStart);
+ }
+ self->branches.erase(curr->in);
+ }
+ self->loopStack.pop_back();
+ }
+
+ static void doEndBreak(SubType* self, Expression** currp) {
+ auto* curr = (*currp)->cast<Break>();
+ self->branches[curr->name].push_back(self->currBasicBlock); // branch to the target
+ auto* last = self->currBasicBlock;
+ doStartBasicBlock(self, currp);
+ if (curr->condition) {
+ self->link(last, self->currBasicBlock); // we might fall through
+ }
+ }
+
+ static void doEndSwitch(SubType* self, Expression** currp) {
+ auto* curr = (*currp)->cast<Switch>();
+ std::set<Name> seen; // we might see the same label more than once; do not spam branches
+ for (Name target : curr->targets) {
+ if (!seen.count(target)) {
+ self->branches[target].push_back(self->currBasicBlock); // branch to the target
+ seen.insert(target);
+ }
+ }
+ if (!seen.count(curr->default_)) {
+ self->branches[curr->default_].push_back(self->currBasicBlock); // branch to the target
+ }
+ doStartBasicBlock(self, currp);
+ }
+
+ static void scan(SubType* self, Expression** currp) {
+ Expression* curr = *currp;
+
+ switch (curr->_id) {
+ case Expression::Id::BlockId: {
+ self->pushTask(SubType::doEndBlock, currp);
+ self->pushTask(SubType::doVisitBlock, currp);
+ auto& list = curr->cast<Block>()->list;
+ for (int i = int(list.size()) - 1; i >= 0; i--) {
+ self->pushTask(SubType::scan, &list[i]);
+ }
+ break;
+ }
+ case Expression::Id::IfId: {
+ self->pushTask(SubType::doEndIf, currp);
+ self->pushTask(SubType::doVisitIf, currp);
+ auto* ifFalse = curr->cast<If>()->ifFalse;
+ if (ifFalse) {
+ self->pushTask(SubType::scan, &curr->cast<If>()->ifFalse);
+ self->pushTask(SubType::doStartIfFalse, currp);
+ }
+ self->pushTask(SubType::scan, &curr->cast<If>()->ifTrue);
+ self->pushTask(SubType::doStartIfTrue, currp);
+ self->pushTask(SubType::scan, &curr->cast<If>()->condition);
+ break;
+ }
+ case Expression::Id::LoopId: {
+ self->pushTask(SubType::doEndLoop, currp);
+ self->pushTask(SubType::doVisitLoop, currp);
+ self->pushTask(SubType::scan, &curr->cast<Loop>()->body);
+ self->pushTask(SubType::doStartLoop, currp);
+ break;
+ }
+ case Expression::Id::BreakId: {
+ self->pushTask(SubType::doEndBreak, currp);
+ self->pushTask(SubType::doVisitBreak, currp);
+ self->maybePushTask(SubType::scan, &curr->cast<Break>()->condition);
+ self->maybePushTask(SubType::scan, &curr->cast<Break>()->value);
+ break;
+ }
+ case Expression::Id::SwitchId: {
+ self->pushTask(SubType::doEndSwitch, currp);
+ self->pushTask(SubType::doVisitSwitch, currp);
+ self->maybePushTask(SubType::scan, &curr->cast<Switch>()->value);
+ self->pushTask(SubType::scan, &curr->cast<Switch>()->condition);
+ break;
+ }
+ case Expression::Id::ReturnId: {
+ self->pushTask(SubType::doStartBasicBlock, currp);
+ self->pushTask(SubType::doVisitReturn, currp);
+ self->maybePushTask(SubType::scan, &curr->cast<Return>()->value);
+ break;
+ }
+ case Expression::Id::UnreachableId: {
+ self->pushTask(SubType::doStartBasicBlock, currp);
+ self->pushTask(SubType::doVisitUnreachable, currp);
+ break;
+ }
+ default: {
+ // other node types do not have control flow, use regular post-order
+ PostWalker<SubType, VisitorType>::scan(self, currp);
+ }
+ }
+ }
+
+ void walk(Expression*& root) {
+ basicBlocks.clear();
+
+ doStartBasicBlock(static_cast<SubType*>(this), nullptr);
+ entry = currBasicBlock;
+ PostWalker<SubType, VisitorType>::walk(root);
+
+ assert(branches.size() == 0);
+ assert(ifStack.size() == 0);
+ assert(loopStack.size() == 0);
+ }
+
+ std::unordered_set<BasicBlock*> findLiveBlocks() {
+ std::unordered_set<BasicBlock*> alive;
+ std::unordered_set<BasicBlock*> queue;
+ queue.insert(entry);
+ while (queue.size() > 0) {
+ auto iter = queue.begin();
+ auto* curr = *iter;
+ queue.erase(iter);
+ alive.insert(curr);
+ for (auto* out : curr->out) {
+ if (!alive.count(out)) queue.insert(out);
+ }
+ }
+ return alive;
+ }
+
+ void unlinkDeadBlocks(std::unordered_set<BasicBlock*> alive) {
+ for (auto& block : basicBlocks) {
+ if (!alive.count(block.get())) {
+ block->in.clear();
+ block->out.clear();
+ continue;
+ }
+ block->in.erase(std::remove_if(block->in.begin(), block->in.end(), [&alive](BasicBlock* other) {
+ return !alive.count(other);
+ }), block->in.end());
+ block->out.erase(std::remove_if(block->out.begin(), block->out.end(), [&alive](BasicBlock* other) {
+ return !alive.count(other);
+ }), block->out.end());
+ }
+ }
+
+ // TODO: utility method for optimizing cfg, removing empty blocks depending on their .content
+
+ std::map<BasicBlock*, size_t> debugIds;
+
+ void dumpCFG(std::string message, Function* func) {
+ std::cout << "<==\nCFG [" << message << "]:\n";
+ for (auto& block : basicBlocks) {
+ debugIds[block.get()] = debugIds.size();
+ }
+ for (auto& block : basicBlocks) {
+ assert(debugIds.count(block.get()) > 0);
+ std::cout << " block " << debugIds[block.get()] << ":\n";
+ block->contents.dump(func);
+ for (auto& in : block->in) {
+ assert(debugIds.count(in) > 0);
+ assert(std::find(in->out.begin(), in->out.end(), block.get()) != in->out.end()); // must be a parallel link back
+ }
+ for (auto& out : block->out) {
+ assert(debugIds.count(out) > 0);
+ std::cout << " out: " << debugIds[out] << "\n";
+ assert(std::find(out->in.begin(), out->in.end(), block.get()) != out->in.end()); // must be a parallel link back
+ }
+ }
+ std::cout << "==>\n";
+ }
+};
+
+} // namespace wasm
+
+#endif // cfg_traversal_h
diff --git a/src/passes/CMakeLists.txt b/src/passes/CMakeLists.txt
index 5c9983dfd..2e830d991 100644
--- a/src/passes/CMakeLists.txt
+++ b/src/passes/CMakeLists.txt
@@ -1,5 +1,6 @@
SET(passes_SOURCES
pass.cpp
+ CoalesceLocals.cpp
LowerIfElse.cpp
MergeBlocks.cpp
Metrics.cpp
diff --git a/src/passes/CoalesceLocals.cpp b/src/passes/CoalesceLocals.cpp
new file mode 100644
index 000000000..006e23984
--- /dev/null
+++ b/src/passes/CoalesceLocals.cpp
@@ -0,0 +1,353 @@
+/*
+ * Copyright 2016 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+//
+// Coalesce locals, in order to reduce the total number of locals. This
+// is similar to register allocation, however, there is never any
+// spilling, and there isn't a fixed number of locals.
+//
+
+
+#include <memory>
+#include <unordered_set>
+
+#include "wasm.h"
+#include "pass.h"
+#include "ast_utils.h"
+#include "cfg/cfg-traversal.h"
+
+namespace wasm {
+
+// A set of locals
+struct LocalSet : std::vector<bool> {
+ LocalSet() {}
+ LocalSet(size_t size) {
+ clear(size);
+ }
+
+ void clear(size_t size) {
+ resize(size);
+ std::fill(begin(), end(), 0);
+ }
+
+ size_t count() {
+ size_t ret = 0;
+ for (size_t i = 0; i < size(); i++) {
+ ret += (*this)[i];
+ }
+ return ret;
+ }
+};
+
+// a liveness-relevant action
+struct Action {
+ enum What {
+ Get, Set
+ };
+ What what;
+ Index index; // the local index read or written
+ Expression** origin; // the origin
+ bool effective; // whether a store is actually effective, i.e., may be read
+
+ Action(What what, Index index, Expression** origin) : what(what), index(index), origin(origin), effective(false) {}
+
+ bool isGet() { return what == Get; }
+ bool isSet() { return what == Set; }
+};
+
+// information about liveness in a basic block
+struct Liveness {
+ LocalSet start, end; // live locals at the start and end
+ std::vector<Action> actions; // actions occurring in this block
+
+ void dump(Function* func) {
+ if (actions.empty()) return;
+ std::cout << " actions:\n";
+ for (auto& action : actions) {
+ std::cout << " " << (action.isGet() ? "get" : "set") << " " << func->getLocalName(action.index) << "\n";
+ }
+ }
+};
+
+struct CoalesceLocals : public WalkerPass<CFGWalker<CoalesceLocals, Visitor<CoalesceLocals>, Liveness>> {
+ bool isFunctionParallel() { return true; }
+
+ Index numLocals;
+
+ BasicBlock* makeBasicBlock() {
+ auto ret = new BasicBlock();
+ ret->contents.start.clear(numLocals);
+ ret->contents.end.clear(numLocals);
+ return ret;
+ }
+
+ // cfg traversal work
+
+ static void doVisitGetLocal(CoalesceLocals* self, Expression** currp) {
+ auto* curr = (*currp)->cast<GetLocal>();
+ self->currBasicBlock->contents.actions.emplace_back(Action::Get, curr->index, currp);
+ }
+
+ static void doVisitSetLocal(CoalesceLocals* self, Expression** currp) {
+ auto* curr = (*currp)->cast<SetLocal>();
+ self->currBasicBlock->contents.actions.emplace_back(Action::Set, curr->index, currp);
+ }
+
+ // main entry point
+
+ void walk(Expression*& root) {
+ numLocals = getFunction()->getNumLocals();
+ // collect initial liveness info
+ WalkerPass<CFGWalker<CoalesceLocals, Visitor<CoalesceLocals>, Liveness>>::walk(root);
+ // ignore links to dead blocks, so they don't confuse us and we can see their stores are all ineffective
+ liveBlocks = findLiveBlocks();
+ unlinkDeadBlocks(liveBlocks);
+#ifdef CFG_DEBUG
+ dumpCFG("the cfg", getFunction());
+#endif
+ // flow liveness across blocks
+ flowLiveness();
+ // pick new indices
+ auto indices = pickIndices();
+ // apply indices
+ applyIndices(indices, root);
+ }
+
+ // inteference state
+
+ LocalSet interferences;
+ std::unordered_set<BasicBlock*> liveBlocks;
+
+ void interfere(Index i, Index j) {
+ if (i == j) return;
+#ifdef CFG_DEBUG
+ if (!interferences[i + j * numLocals]) {
+ std::cout << getFunction()->name << ": interfere " << getFunction()->getLocalName(std::min(i, j)) << " : " << getFunction()->getLocalName(std::max(i, j)) << "\n";
+ }
+#endif
+ interferences[i + j * numLocals] = 1;
+ interferences[j + i * numLocals] = 1;
+ }
+
+ void flowLiveness() {
+ interferences.clear(numLocals * numLocals);
+ // keep working while stuff is flowing
+ std::vector<BasicBlock*> queue; // TODO set to avoid inserting same block more than once at a time period. TODO optimize, an order might be more efficient
+ for (auto& curr : basicBlocks) {
+ if (liveBlocks.count(curr.get()) == 0) continue; // ignore dead blocks
+ queue.push_back(curr.get());
+ // do the first scan through the block, starting with nothing live at the end, and updating the liveness at the start
+ scanLivenessThroughActions(curr->contents.actions, curr->contents.start);
+ }
+ // at every point in time, we assume we already noted interferences between things already known alive at the end, and scanned back throught the block using that
+ while (queue.size() > 0) {
+ auto* curr = queue.back(); // TODO: order?
+ queue.pop_back();
+ LocalSet live(numLocals);
+ if (!mergeStartsAndCheckChange(curr->out, curr->contents.end, live)) continue;
+#ifdef CFG_DEBUG
+ std::cout << "change noticed at end of " << debugIds[curr] << " from " << curr->contents.end.count() << " to " << live.count() << " (out of " << numLocals << ")\n";
+#endif
+ assert(curr->contents.end.count() < live.count());
+ curr->contents.end = live;
+ scanLivenessThroughActions(curr->contents.actions, live);
+ // liveness is now calculated at the start. if something
+ // changed, all predecessor blocks need recomputation
+ if (curr->contents.start == live) continue;
+#ifdef CFG_DEBUG
+ std::cout << "change noticed at start of " << debugIds[curr] << " from " << curr->contents.start.count() << " to " << live.count() << ", more work to do\n";
+#endif
+ assert(curr->contents.start.count() < live.count());
+ curr->contents.start = live;
+ for (auto* in : curr->in) {
+ queue.push_back(in);
+#ifdef CFG_DEBUG_ORDER
+ // alternative code for changing the flow order; results must be the same, as we detect a property of the graph.
+ if (queue.empty()) {
+ queue.push_back(in);
+ } else {
+ //abort();
+ auto* front = queue[0];
+ queue[0] = in;
+ queue.push_back(front);
+ }
+#endif
+ }
+ }
+ // live locals at the entry block include params, obviously, but also
+ // vars, in which case the 0-init value is actually used.
+#ifdef CFG_DEBUG
+ std::hash<std::vector<bool>> hasher;
+ std::cout << getFunction()->name << ": interference hash: " << hasher(*(std::vector<bool>*)&interferences) << "\n";
+ for (size_t i = 0; i < numLocals; i++) {
+ std::cout << "int for " << getFunction()->getLocalName(i) << " [" << i << "]: ";
+ for (size_t j = 0; j < numLocals; j++) {
+ assert(interferences[i * numLocals + j] == interferences[j * numLocals + i]);
+ if (interferences[i * numLocals + j]) std::cout << getFunction()->getLocalName(j) << " ";
+ }
+ std::cout << "\n";
+ }
+#endif
+ }
+
+ // merge starts of a list of blocks, adding new interferences as necessary. return
+ // whether anything changed vs an old state (which indicates further processing is necessary).
+ bool mergeStartsAndCheckChange(std::vector<BasicBlock*>& blocks, LocalSet& old, LocalSet& ret) {
+ // merge all the live locals, and add interferences that show up from the merging.
+ // we can assume that locals live together already are already known to be in conflict.
+ if (blocks.size() == 0) return false;
+ if (blocks.size() == 1) {
+ // new interferences are impossible, they would have already been in conflict in the single predecessor.
+ ret = blocks[0]->contents.start;
+ return old != ret;
+ }
+ // more than one, so we must merge
+ for (auto* block : blocks) {
+ for (size_t i = 0; i < numLocals; i++) {
+ ret[i] = ret[i] || block->contents.start[i]; // TODO: optimize
+ }
+ }
+ // If there is no change in the merged result, then no new conflicts are possible.
+ // Assume the opposite, that we would be missing a conflict between x and y. Then
+ // since the merged result has not changed, x and y were present before as well.
+ // If they were present in the same origin block, then they were already in
+ // conflict there, and it is not a new conflict. If not, then they each arrive
+ // from different origins, with x arriving from X = { b_0..b_i } and y arriving from
+ // Y = { b_i+1..b_j }, where all those blocks are unique (since x and y never arrive from
+ // the same block, by assumption). Livenesses are monotonic, i.e., flowing only adds
+ // locals, never removes, so compared to the past state, we only added to X and Y.
+ // Mark the past arrivals X' and Y', and note that those two cannot be empty, since
+ // by assumption the merged result has not changed - x and y were already present
+ // before. But that means that x and y were already in conflict in the past, so
+ // this is not a new conflict.
+ if (ret == old) return false;
+ // look for conflicts TODO: optimize
+ for (size_t i = 0; i < numLocals; i++) {
+ for (size_t j = 0; j < numLocals; j++) {
+ if (ret[i] && ret[j]) interfere(i, j);
+ }
+ }
+ return true;
+ }
+
+ void scanLivenessThroughActions(std::vector<Action>& actions, LocalSet& live) {
+ // move towards the front
+ for (int i = int(actions.size()) - 1; i >= 0; i--) {
+ auto& action = actions[i];
+ if (action.isGet()) {
+ // new live local, interferes with all the rest
+ for (size_t i = 0; i < numLocals; i++) { // TODO: vector?
+ if (live[i]) interfere(i, action.index);
+ }
+ live[action.index] = 1;
+ } else {
+ if (live[action.index]) {
+ action.effective = true;
+ live[action.index] = 0;
+ }
+ }
+ }
+ }
+
+ // Indices decision making
+
+ std::vector<Index> pickIndices() { // returns a vector of oldIndex => newIndex
+ // simple greedy coloring
+ // TODO: multiple orderings
+ // TODO: take into account eliminated copies
+ // TODO: take into account distribution (99-1 is better than 50-50 with two registers, for gzip)
+ std::vector<Index> indices; // old => new
+ std::vector<WasmType> types;
+ LocalSet newInterferences; // new index * numLocals => list of all interferences of locals merged to it
+ indices.resize(numLocals);
+ types.resize(numLocals);
+ newInterferences.resize(numLocals * numLocals);
+ Index nextFree = 0;
+ // we can't reorder parameters, they are fixed in order, and cannot coalesce
+ auto numParams = getFunction()->getNumParams();
+ Index i = 0;
+ for (; i < numParams; i++) {
+ indices[i] = i;
+ types[i] = getFunction()->getLocalType(i);
+ std::copy(interferences.begin() + numLocals * i, interferences.begin() + numLocals * (i + 1), newInterferences.begin() + numLocals * i);
+ nextFree++;
+ }
+ for (; i < numLocals; i++) {
+ Index found = -1;
+ for (Index j = 0; j < nextFree; j++) {
+ if (!newInterferences[j * numLocals + i] && getFunction()->getLocalType(i) == types[j]) {
+ indices[i] = found = j;
+ break;
+ }
+ }
+ if (found == Index(-1)) {
+ indices[i] = found = nextFree;
+ types[found] = getFunction()->getLocalType(i);
+ nextFree++;
+ }
+ // merge new interferences for the new index
+ for (size_t j = 0; j < numLocals; j++) {
+ newInterferences[found * numLocals + j] = newInterferences[found * numLocals + j] | interferences[i * numLocals + j];
+ }
+ }
+ return indices;
+ }
+
+ void applyIndices(std::vector<Index>& indices, Expression* root) {
+ assert(indices.size() == numLocals);
+ for (auto& curr : basicBlocks) {
+ auto& actions = curr->contents.actions;
+ for (auto& action : actions) {
+ if (action.isGet()) {
+ auto* get = (*action.origin)->cast<GetLocal>();
+ get->index = indices[get->index];
+ } else {
+ auto* set = (*action.origin)->cast<SetLocal>();
+ set->index = indices[set->index];
+ // in addition, we can optimize out redundant copies and ineffective sets
+ GetLocal* get;
+ if ((get = set->value->dynCast<GetLocal>()) && get->index == set->index) {
+ *action.origin = get; // further optimizations may get rid of the get, if this is in a place where the output does not matter
+ } else if (!action.effective) {
+ *action.origin = set->value; // value may have no side effects, further optimizations can eliminate it
+ }
+ }
+ }
+ }
+ // update type list
+ auto numParams = getFunction()->getNumParams();
+ Index newNumLocals = 0;
+ for (auto index : indices) {
+ newNumLocals = std::max(newNumLocals, index + 1);
+ }
+ auto oldVars = getFunction()->vars;
+ getFunction()->vars.resize(newNumLocals - numParams);
+ for (size_t index = numParams; index < numLocals; index++) {
+ Index newIndex = indices[index];
+ if (newIndex >= numParams) {
+ getFunction()->vars[newIndex - numParams] = oldVars[index - numParams];
+ }
+ }
+ // names are gone
+ getFunction()->localNames.clear();
+ getFunction()->localIndices.clear();
+ }
+};
+
+static RegisterPass<CoalesceLocals> registerPass("coalesce-locals", "reduce # of locals by coalescing");
+
+} // namespace wasm
diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index e4cc35554..baa59489a 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -62,6 +62,7 @@ void PassRunner::addDefaultOptimizationPasses() {
add("remove-unused-names");
add("optimize-instructions");
add("simplify-locals");
+ add("coalesce-locals");
add("merge-blocks");
add("reorder-locals");
add("vacuum");
diff --git a/src/tools/wasm-as.cpp b/src/tools/wasm-as.cpp
index 40839ea55..e5f5af085 100644
--- a/src/tools/wasm-as.cpp
+++ b/src/tools/wasm-as.cpp
@@ -53,7 +53,7 @@ int main(int argc, const char *argv[]) {
SExpressionWasmBuilder builder(wasm, *root[0]);
} catch (ParseException& p) {
p.dump(std::cerr);
- Fatal() << "error in parsing wasm binary";
+ Fatal() << "error in parsing input";
}
if (options.debug) std::cerr << "binarification..." << std::endl;
generated by cgit v1.2.3 (git 2.39.1) at 2025-08-06 22:55:33 +0000