fix Const finalization and use it properly in br finalization in Precompute

Author: kripken

src/passes/Precompute.cpp

@@ -100,6 +100,7 @@ struct Precompute : public WalkerPass<PostWalker<Precompute, UnifiedExpressionVi
             if (ret->value) {
               if (auto* value = ret->value->dynCast<Const>()) {
                 value->value = flow.value;
+                value->finalize();
                 return;
               }
             }
@@ -117,19 +118,21 @@ struct Precompute : public WalkerPass<PostWalker<Precompute, UnifiedExpressionVi
       if (auto* br = curr->dynCast<Break>()) {
         br->name = flow.breakTo;
         br->condition = nullptr;
-        br->finalize(); // if we removed a condition, the type may change
         if (flow.value.type != none) {
           // reuse a const value if there is one
           if (br->value) {
             if (auto* value = br->value->dynCast<Const>()) {
               value->value = flow.value;
+              value->finalize();
+              br->finalize();
               return;
             }
           }
           br->value = Builder(*getModule()).makeConst(flow.value);
         } else {
           br->value = nullptr;
         }
+        br->finalize();
       } else {
         Builder builder(*getModule());
         replaceCurrent(builder.makeBreak(flow.breakTo, flow.value.type != none ? builder.makeConst(flow.value) : nullptr));

src/wasm.h

@@ -464,6 +464,8 @@ class Const : public SpecificExpression<Expression::ConstId> {
   Literal value;
 
   Const* set(Literal value_);
+
+  void finalize();
 };
 
 class Unary : public SpecificExpression<Expression::UnaryId> {

src/wasm/wasm.cpp

@@ -371,6 +371,10 @@ Const* Const::set(Literal value_) {
   return this;
 }
 
+void Const::finalize() {
+  type = value.type;
+}
+
 bool Unary::isRelational() {
   return op == EqZInt32 || op == EqZInt64;
 }

test/passes/precompute.txt

@@ -2,6 +2,7 @@
  (type $0 (func (param i32)))
  (type $1 (func (result i32)))
  (type $2 (func))
+ (type $3 (func (result f64)))
  (memory $0 0)
  (func $x (type $0) (param $x i32)
   (call $x
@@ -129,4 +130,31 @@
    )
   )
  )
+ (func $reuse-br-value (type $3) (result f64)
+  (block $label$0 (result f64)
+   (i32.store8
+    (i32.const 1919623207)
+    (if (result i32)
+     (i32.const 1)
+     (block $label$2
+      (drop
+       (i64.and
+        (i64.trunc_u/f32
+         (f32.const 70847791997969805621592064)
+        )
+        (i64.const 729618461987467893)
+       )
+      )
+      (br $label$0
+       (f64.const 6.134856208230095e-154)
+      )
+     )
+     (i32.load offset=3 align=2
+      (i32.const 169901344)
+     )
+    )
+   )
+   (f64.const 4776014875438170098655851e156)
+  )
+ )
 )

test/passes/precompute.wast

@@ -210,4 +210,43 @@
     )
    )
   )
+  (func $reuse-br-value (result f64)
+   (block $label$0 (result f64)
+    (i32.store8
+     (i32.const 1919623207)
+     (if (result i32)
+      (i32.const 1)
+      (block $label$2 (result i32)
+       (drop
+        (i64.and
+         (i64.trunc_u/f32
+          (f32.const 70847791997969805621592064)
+         )
+         (i64.const 729618461987467893)
+        )
+       )
+       (br_if $label$2
+        (i32.const 2049535349)
+        (f32.eq
+         (f32.demote/f64
+          (f64.mul
+           (br_if $label$0 ;; this br is optimized, and br *and* values reused
+            (f64.const 6.134856208230095e-154)
+            (i32.const 690910817)
+           )
+           (f64.const 1.515470884183969e-152)
+          )
+         )
+         (f32.const 66524025679377434935296)
+        )
+       )
+      )
+      (i32.load offset=3 align=2
+        (i32.const 169901344)
+      )
+     )
+    )
+    (f64.const 4776014875438170098655851e156)
+   )
+  )
 )