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//
// WebAssembly-to-asm.js translator. Uses the Emscripten optimizer
// infrastructure.
//
#include "wasm.h"
#include "emscripten-optimizer/optimizer.h"
#include "mixed_arena.h"
namespace wasm {
using namespace cashew;
IString ASM_FUNC("asmFunc");
//
// Wasm2AsmBuilder - converts a WebAssembly module into asm.js
//
class Wasm2AsmBuilder {
MixedArena& allocator;
// How many temp vars we need
int i32s = 0, f32s = 0, f64s = 0;
public:
Asm2WasmBuilder(MixedArena& allocator) : allocator(allocator) {}
Ref processWasm(Module* wasm);
Ref processFunction(Function* func);
//
// Tracks state while converting a function. We need to add new
// temporaries, and overall handle the fact that statements ==
// expressions in wasm, but not asm.js. That means that a wasm
// expression may be turned into an asm.js statement, which we
// cannot just place into an expression, but need to keep
// creating statements until we reach a statement context.
//
// @param result Whether the context we are in receives a value,
// and its type, or if not, then we can drop our return,
// if we have one.
Ref processExpression(Expression* curr, WasmType result);
// Get a temp var.
IString getTemp(WasmType type);
// Free a temp var.
void freeTemp(IString temp);
// Get and immediately free a temp var.
IString getTempAndFree(WasmType type);
};
Ref Wasm2AsmBuilder::processWasm(Module* wasm) {
Ref ret = ValueBuilder::makeTopLevel();
Ref asmFunc = ValueBuilder::makeFunction();
asmFunc[1] = ValueBuilder::makeRawString(ASM_FUNC);
ret[1]->push_back(asmFunc);
// imports XXX
// exports XXX
// functions
for (auto func : wasm->functions) {
asmFunc[3]->push_back(processFunction(func));
}
// table XXX
// memory XXX
return ret;
}
Ref Wasm2AsmBuilder::processFunction(Function* func) {
Ref ret = ValueBuilder::makeFunction();
ret[1] = ValueBuilder::makeRawString(func->name);
// arguments XXX
// body
ret[3]->push_back(processExpression(func->body, func->result));
// locals, including new temp locals XXX
return ret;
}
Ref Wasm2AsmBuilder::processExpression(Expression* curr) {
struct ExpressionProcessor : public WasmVisitor<Ref> {
Wasm2AsmBuilder* parent;
WasmType result;
ExpressionProcessor(Wasm2AsmBuilder* parent, WasmType result) : parent(parent), result(result) {}
// Expressions with control flow turn into a block, which we must
// then handle, even if we are an expression.
bool isBlock(Ref ast) {
return ast[0] == BLOCK;
}
// Looks for a standard assign at the end of a block, which if this
// block returns a value, it will have.
Ref getBlockAssign(Ref ast) {
if (!(ast.size() >= 2 && ast[1].size() > 0)) return Ref();
Ref last = deStat(ast[1][ast[1].size()-1]);
if (!(last[0] == ASSIGN && last[2][0] == NAME)) return Ref;
return last;
}
// If we replace an expression with a block, and we need to return
// a value, it will show up in the last element, as an assign. This
// returns it.
IString getBlockValue(Ref ast) {
Ref assign = getBlockAssign(ast);
assert(!!assign);
return assign[2][1]->getIString();
}
Ref blockify(Ref ast) {
if (isBlock(ast)) return ast;
Ref ret = ValueBuilder::makeBlock();
ret[1]->push_back(ast);
return ret;
}
Ref blockifyWithResult(Ref ast, IString temp) {
if (isBlock(ast)) {
Ref assign = getBlockAssign(ast);
assert(!!assign); // if a block, must have a value returned
assign[2][1]->setString(temp); // replace existing assign target
return ast;
}
// not a block, so an expression. Just assign to the temp var.
Ref ret = ValueBuilder::makeBlock();
ret[1]->push_back(makeAssign(makeName(temp), ast));
return ret;
}
// Visitors
void visitBlock(Block *curr) override {
Ref ret = ValueBuilder::makeBlock();
size_t size = curr->list.size();
for (size_t i = 0; i < size; i++) {
ret[1]->push_back(processExpression(func->body, i < size-1 ? false : result);
}
return ret;
}
void visitIf(If *curr) override {
assert(result ? !!curr->ifFalse : true); // an if without an else cannot be in a receiving context
Ref condition = processExpression(curr->condition, result);
Ref ifTrue = processExpression(curr->ifTrue, result);
Ref ifFalse;
if (curr->ifFalse) {
ifFalse = processExpression(curr->ifFalse, result);
}
if (result != none) {
IString temp = parent->getTempAndFree(result);
ifTrue = blockifyWithResult(ifTrue, temp);
if (curr->ifFalse) ifFalse = blockifyWithResult(ifFalse, temp);
}
if (!isBlock(condition)) {
return ValueBuilder::makeIf(condition, ifTrue, ifFalse); // simple if
}
// just add an if to the block
condition[1]->push_back(ValueBuilder::makeIf(getBlockValue(condition), ifTrue, ifFalse));
return condition;
}
void visitLoop(Loop *curr) override {
}
void visitLabel(Label *curr) override {
}
void visitBreak(Break *curr) override {
}
void visitSwitch(Switch *curr) override {
}
void visitCall(Call *curr) override {
}
void visitCallImport(CallImport *curr) override {
}
void visitCallIndirect(CallIndirect *curr) override {
}
void visitGetLocal(GetLocal *curr) override {
}
void visitSetLocal(SetLocal *curr) override {
}
void visitLoad(Load *curr) override {
}
void visitStore(Store *curr) override {
}
void visitConst(Const *curr) override {
}
void visitUnary(Unary *curr) override {
}
void visitBinary(Binary *curr) override {
}
void visitCompare(Compare *curr) override {
}
void visitConvert(Convert *curr) override {
}
void visitSelect(Select *curr) override {
}
void visitHost(Host *curr) override {
}
void visitNop(Nop *curr) override {
}
void visitUnreachable(Unreachable *curr) override {
}
};
return ExpressionProcessor(this, result).visit(curr);
}
} // namespace wasm
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