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.

Author: aheejin

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;
     }

test/passes/alignment-lowering.txt

@@ -437,7 +437,7 @@
    )
   )
   (drop
-   (unreachable.load offset=100
+   (i32.load offset=100
     (unreachable)
    )
   )

test/passes/flatten.txt

@@ -679,7 +679,7 @@
    (drop
     (unreachable)
    )
-   (unreachable.load
+   (i32.load
     (unreachable)
    )
    (unreachable)
@@ -1183,7 +1183,7 @@
     (i32.const 22)
     (block
      (unreachable)
-     (unreachable.load
+     (i32.load
       (unreachable)
      )
      (drop

test/passes/remove-unused-brs.txt

@@ -984,7 +984,7 @@
      (i32.const 607395945)
     )
     (br_if $label$1
-     (unreachable.load offset=3 align=1
+     (i32.load offset=3 align=1
       (select
        (call $untaken-brs-might-prevent-block-removal
         (f32.const 1.4904844647389837e-07)

test/unreachable-instr-type.wast

@@ -0,0 +1,28 @@
+(module
+  (memory (shared 1 1))
+  (func $test
+    (f32.load (unreachable))
+
+    (f32.store
+      (unreachable)
+      (f32.const 0)
+    )
+
+    (i64.atomic.rmw.add
+      (unreachable)
+      (i64.const 0)
+    )
+
+    (i64.atomic.rmw.cmpxchg
+      (unreachable)
+      (i64.const 0)
+      (i64.const 1)
+    )
+
+    (i64.atomic.wait
+      (unreachable)
+      (i64.const 0)
+      (i64.const 0)
+    )
+  )
+)

test/unreachable-instr-type.wast.from-wast

@@ -0,0 +1,27 @@
+(module
+ (type $FUNCSIG$v (func))
+ (memory $0 (shared 1 1))
+ (func $test (; 0 ;) (type $FUNCSIG$v)
+  (i32.load
+   (unreachable)
+  )
+  (f32.store
+   (unreachable)
+   (f32.const 0)
+  )
+  (i32.atomic.rmw.add
+   (unreachable)
+   (i64.const 0)
+  )
+  (i32.atomic.rmw.cmpxchg
+   (unreachable)
+   (i64.const 0)
+   (i64.const 1)
+  )
+  (i64.atomic.wait
+   (unreachable)
+   (i64.const 0)
+   (i64.const 0)
+  )
+ )
+)

test/unreachable-instr-type.wast.fromBinary

@@ -0,0 +1,8 @@
+(module
+ (type $0 (func))
+ (memory $0 (shared 1 1))
+ (func $test (; 0 ;) (type $0)
+  (unreachable)
+ )
+)
+

test/unreachable-instr-type.wast.fromBinary.noDebugInfo

@@ -0,0 +1,8 @@
+(module
+ (type $0 (func))
+ (memory $0 (shared 1 1))
+ (func $0 (; 0 ;) (type $0)
+  (unreachable)
+ )
+)
+