Support control flow inputs in IRBuilder (#7149)

Since multivalue was standardized, WebAssembly has supported not only
multiple results but also an arbitrary number of inputs on control flow
structures, but until now Binaryen did not support control flow input.
Binaryen IR still has no way to represent control flow input, so lower
it away using scratch locals in IRBuilder. Since both the text and
binary parsers use IRBuilder, this gives us full support for parsing
control flow inputs.

The lowering scheme is mostly simple. A local.set writing the control
flow inputs to a scratch local is inserted immediately before the
control flow structure begins and a local.get retrieving those inputs is
inserted inside the control flow structure before the rest of its body.
The only complications come from ifs, in which the inputs must be
retrieved at the beginning of both arms, and from loops, where branches
to the beginning of the loop must be transformed so their values are
written to the scratch local along the way.

Resolves #6407.

1 files changed, 20 insertions, 20 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 0c931f518..791dc53d7 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -2121,30 +2121,30 @@ bool WasmBinaryReader::getBasicHeapType(int64_t code, HeapType& out) {
   }
 }
 
-Type WasmBinaryReader::getType(int initial) {
-  // Single value types are negative; signature indices are non-negative
-  if (initial >= 0) {
-    // TODO: Handle block input types properly.
-    auto sig = getSignatureByTypeIndex(initial);
-    if (sig.params != Type::none) {
-      throwError("control flow inputs are not supported yet");
-    }
-    return sig.results;
+Signature WasmBinaryReader::getBlockType() {
+  // Single value types are negative; signature indices are non-negative.
+  auto code = getS32LEB();
+  if (code >= 0) {
+    return getSignatureByTypeIndex(code);
+  }
+  if (code == BinaryConsts::EncodedType::Empty) {
+    return Signature();
   }
+  return Signature(Type::none, getType(code));
+}
+
+Type WasmBinaryReader::getType(int code) {
   Type type;
-  if (getBasicType(initial, type)) {
+  if (getBasicType(code, type)) {
     return type;
   }
-  switch (initial) {
-    // None only used for block signatures. TODO: Separate out?
-    case BinaryConsts::EncodedType::Empty:
-      return Type::none;
+  switch (code) {
     case BinaryConsts::EncodedType::nullable:
       return Type(getHeapType(), Nullable);
     case BinaryConsts::EncodedType::nonnullable:
       return Type(getHeapType(), NonNullable);
     default:
-      throwError("invalid wasm type: " + std::to_string(initial));
+      throwError("invalid wasm type: " + std::to_string(code));
   }
   WASM_UNREACHABLE("unexpected type");
 }
@@ -2885,11 +2885,11 @@ Result<> WasmBinaryReader::readInst() {
   uint8_t code = getInt8();
   switch (code) {
     case BinaryConsts::Block:
-      return builder.makeBlock(Name(), getType());
+      return builder.makeBlock(Name(), getBlockType());
     case BinaryConsts::If:
-      return builder.makeIf(Name(), getType());
+      return builder.makeIf(Name(), getBlockType());
     case BinaryConsts::Loop:
-      return builder.makeLoop(Name(), getType());
+      return builder.makeLoop(Name(), getBlockType());
     case BinaryConsts::Br:
       return builder.makeBreak(getU32LEB(), false);
     case BinaryConsts::BrIf:
@@ -2974,9 +2974,9 @@ Result<> WasmBinaryReader::readInst() {
     case BinaryConsts::TableSet:
       return builder.makeTableSet(getTableName(getU32LEB()));
     case BinaryConsts::Try:
-      return builder.makeTry(Name(), getType());
+      return builder.makeTry(Name(), getBlockType());
     case BinaryConsts::TryTable: {
-      auto type = getType();
+      auto type = getBlockType();
       std::vector<Name> tags;
       std::vector<Index> labels;
       std::vector<bool> isRefs;