Fix unreachable prefix in instruction printing (#2265)

When a memory instruction's type is unreachable, i.e., one of its
child expressions is unreachable, the instruction will be printed like
`unreachable.load`, which is invalid text format.

This prints unreachable prefix instruction types as `i32` to just make
them pass the parser. It is OK because they are not reachable anyway.
Also this removes printing of `?` in atomic.rmw instruction printing.

1 files changed, 11 insertions, 7 deletions

diff --git a/src/passes/Print.cpp b/src/passes/Print.cpp
index 0c71afc7b..dc973b208 100644
--- a/src/passes/Print.cpp
+++ b/src/passes/Print.cpp
@@ -55,6 +55,12 @@ static Name printableLocal(Index index, Function* func) {
   return name;
 }
 
+// Printing "unreachable" as a instruction prefix type is not valid in wasm text
+// format. Print something else to make it pass.
+static Type forceConcrete(Type type) {
+  return isConcreteType(type) ? type : i32;
+}
+
 // Prints the internal contents of an expression: everything but
 // the children.
 struct PrintExpressionContents
@@ -141,7 +147,7 @@ struct PrintExpressionContents
     printName(curr->name, o);
   }
   void visitLoad(Load* curr) {
-    prepareColor(o) << printType(curr->type);
+    prepareColor(o) << printType(forceConcrete(curr->type));
     if (curr->isAtomic) {
       o << ".atomic";
     }
@@ -167,7 +173,7 @@ struct PrintExpressionContents
     }
   }
   void visitStore(Store* curr) {
-    prepareColor(o) << printType(curr->valueType);
+    prepareColor(o) << printType(forceConcrete(curr->valueType));
     if (curr->isAtomic) {
       o << ".atomic";
     }
@@ -192,10 +198,8 @@ struct PrintExpressionContents
     }
   }
   static void printRMWSize(std::ostream& o, Type type, uint8_t bytes) {
-    prepareColor(o) << printType(type) << ".atomic.rmw";
-    if (type == unreachable) {
-      o << '?';
-    } else if (bytes != getTypeSize(type)) {
+    prepareColor(o) << printType(forceConcrete(type)) << ".atomic.rmw";
+    if (type != unreachable && bytes != getTypeSize(type)) {
       if (bytes == 1) {
         o << '8';
       } else if (bytes == 2) {
@@ -253,7 +257,7 @@ struct PrintExpressionContents
   }
   void visitAtomicWait(AtomicWait* curr) {
     prepareColor(o);
-    o << printType(curr->expectedType) << ".atomic.wait";
+    o << printType(forceConcrete(curr->expectedType)) << ".atomic.wait";
     if (curr->offset) {
       o << " offset=" << curr->offset;
     }