refactor get_local counting out of simplify-locals (#812)

2 files changed, 57 insertions, 19 deletions

diff --git a/src/ast/count.h b/src/ast/count.h
new file mode 100644
index 000000000..56f281ce6
--- /dev/null
+++ b/src/ast/count.h
@@ -0,0 +1,50 @@
+/*
+ * 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.
+ */
+
+#ifndef wasm_ast_count_h
+#define wasm_ast_count_h
+
+namespace wasm {
+
+struct GetLocalCounter : public PostWalker<GetLocalCounter, Visitor<GetLocalCounter>> {
+  std::vector<Index> num;
+
+  GetLocalCounter() {}
+  GetLocalCounter(Function* func) {
+    analyze(func, func->body);
+  }
+  GetLocalCounter(Function* func, Expression* ast) {
+    analyze(func, ast);
+  }
+
+  void analyze(Function* func) {
+    analyze(func, func->body);
+  }
+  void analyze(Function* func, Expression* ast) {
+    num.resize(func->getNumLocals());
+    std::fill(num.begin(), num.end(), 0);
+    walk(ast);
+  }
+
+  void visitGetLocal(GetLocal *curr) {
+    num[curr->index]++;
+  }
+};
+
+} // namespace wasm
+
+#endif // wasm_ast_count_h
+
diff --git a/src/passes/SimplifyLocals.cpp b/src/passes/SimplifyLocals.cpp
index 17206af89..7fef53dcc 100644
--- a/src/passes/SimplifyLocals.cpp
+++ b/src/passes/SimplifyLocals.cpp
@@ -37,19 +37,12 @@
 #include <wasm-traversal.h>
 #include <pass.h>
 #include <ast_utils.h>
+#include <ast/count.h>
 
 namespace wasm {
 
 // Helper classes
 
-struct GetLocalCounter : public PostWalker<GetLocalCounter, Visitor<GetLocalCounter>> {
-  std::vector<Index>* numGetLocals;
-
-  void visitGetLocal(GetLocal *curr) {
-    (*numGetLocals)[curr->index]++;
-  }
-};
-
 struct SetLocalRemover : public PostWalker<SetLocalRemover, Visitor<SetLocalRemover>> {
   std::vector<Index>* numGetLocals;
 
@@ -118,7 +111,7 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
   bool firstCycle;
 
   // local => # of get_locals for it
-  std::vector<Index> numGetLocals;
+  GetLocalCounter counter;
 
   static void doNoteNonLinear(SimplifyLocals* self, Expression** currp) {
     auto* curr = *currp;
@@ -195,7 +188,7 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
       auto* set = (*found->second.item)->cast<SetLocal>();
       if (firstCycle) {
         // just one get_local of this, so just sink the value
-        assert(numGetLocals[curr->index] == 1);
+        assert(counter.num[curr->index] == 1);
         replaceCurrent(set->value);
       } else {
         replaceCurrent(set);
@@ -271,7 +264,7 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
       self->checkInvalidations(effects);
     }
 
-    if (set && !set->isTee() && (!self->firstCycle || self->numGetLocals[set->index] == 1)) {
+    if (set && !set->isTee() && (!self->firstCycle || self->counter.num[set->index] == 1)) {
       Index index = set->index;
       assert(self->sinkables.count(index) == 0);
       self->sinkables.emplace(std::make_pair(index, SinkableInfo(currp)));
@@ -422,11 +415,7 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
 
   void doWalkFunction(Function* func) {
     // scan get_locals
-    numGetLocals.resize(func->getNumLocals());
-    std::fill(numGetLocals.begin(), numGetLocals.end(), 0);
-    GetLocalCounter counter;
-    counter.numGetLocals = &numGetLocals;
-    counter.walkFunction(func);
+    counter.analyze(func);
     // multiple passes may be required per function, consider this:
     //    x = load
     //    y = store
@@ -479,11 +468,10 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
     // for a local with no remaining gets, in which case, we can
     // remove the set.
     // First, recount get_locals
-    std::fill(numGetLocals.begin(), numGetLocals.end(), 0);
-    counter.walkFunction(func);
+    counter.analyze(func);
     // Second, remove unneeded sets
     SetLocalRemover remover;
-    remover.numGetLocals = &numGetLocals;
+    remover.numGetLocals = &counter.num;
     remover.walkFunction(func);
   }
 };