Fix invalid flow assumption in 'if' compilation (#1244)

Author: dcodeIO

src/compiler.ts

@@ -2581,11 +2581,7 @@ export class Compiler extends DiagnosticEmitter {
       }
       elseFlow.freeScopedLocals();
       this.currentFlow = flow;
-      if (elseTerminates && !thenTerminates) {
-        flow.inherit(thenFlow);
-      } else {
-        flow.inheritMutual(thenFlow, elseFlow);
-      }
+      flow.inheritMutual(thenFlow, elseFlow);
       return module.if(condExpr,
         module.flatten(thenStmts),
         module.flatten(elseStmts)

tests/compiler/while.optimized.wat

@@ -1415,6 +1415,36 @@
    call $~lib/builtins/abort
    unreachable
   end
+  i32.const 0
+  global.set $while/ran
+  i32.const 0
+  local.set $3
+  loop $while-continue|067
+   local.get $3
+   i32.const 1
+   i32.add
+   local.tee $3
+   i32.const 1
+   i32.lt_s
+   br_if $while-continue|067
+  end
+  i32.const 1
+  global.set $while/ran
+  i32.const 0
+  global.set $while/ran
+  i32.const 0
+  local.set $3
+  loop $while-continue|08
+   local.get $3
+   i32.const 1
+   i32.add
+   local.tee $3
+   i32.const 1
+   i32.lt_s
+   br_if $while-continue|08
+  end
+  i32.const 1
+  global.set $while/ran
  )
  (func $~start
   global.get $~started

tests/compiler/while.ts

@@ -175,3 +175,35 @@ function testRefAutorelease(): void {
 ran = false;
 testRefAutorelease();
 assert(ran);
+
+function testIfImplicitContinueThen(): void {
+  var i = 0;
+  while (true) {
+    i++;
+    if (i < 1) {
+      // continue
+    } else {
+      break;
+    }
+  }
+  ran = true;
+}
+ran = false;
+testIfImplicitContinueThen();
+assert(ran);
+
+function testIfImplicitContinueElse(): void {
+  var i = 0;
+  while (true) {
+    i++;
+    if (i >= 1) {
+      break;
+    } else {
+      // continue
+    }
+  }
+  ran = true;
+}
+ran = false;
+testIfImplicitContinueElse();
+assert(ran);

tests/compiler/while.untouched.wat

@@ -2154,6 +2154,66 @@
   local.get $1
   call $~lib/rt/pure/__release
  )
+ (func $while/testIfImplicitContinueThen
+  (local $0 i32)
+  (local $1 i32)
+  i32.const 0
+  local.set $0
+  block $while-break|0
+   loop $while-continue|0
+    i32.const 1
+    local.set $1
+    local.get $1
+    if
+     local.get $0
+     i32.const 1
+     i32.add
+     local.set $0
+     local.get $0
+     i32.const 1
+     i32.lt_s
+     if
+      nop
+     else
+      br $while-break|0
+     end
+     br $while-continue|0
+    end
+   end
+  end
+  i32.const 1
+  global.set $while/ran
+ )
+ (func $while/testIfImplicitContinueElse
+  (local $0 i32)
+  (local $1 i32)
+  i32.const 0
+  local.set $0
+  block $while-break|0
+   loop $while-continue|0
+    i32.const 1
+    local.set $1
+    local.get $1
+    if
+     local.get $0
+     i32.const 1
+     i32.add
+     local.set $0
+     local.get $0
+     i32.const 1
+     i32.ge_s
+     if
+      br $while-break|0
+     else
+      nop
+     end
+     br $while-continue|0
+    end
+   end
+  end
+  i32.const 1
+  global.set $while/ran
+ )
  (func $start:while
   i32.const 0
   global.set $while/ran
@@ -2310,6 +2370,32 @@
    call $~lib/builtins/abort
    unreachable
   end
+  i32.const 0
+  global.set $while/ran
+  call $while/testIfImplicitContinueThen
+  global.get $while/ran
+  i32.eqz
+  if
+   i32.const 0
+   i32.const 32
+   i32.const 193
+   i32.const 1
+   call $~lib/builtins/abort
+   unreachable
+  end
+  i32.const 0
+  global.set $while/ran
+  call $while/testIfImplicitContinueElse
+  global.get $while/ran
+  i32.eqz
+  if
+   i32.const 0
+   i32.const 32
+   i32.const 209
+   i32.const 1
+   call $~lib/builtins/abort
+   unreachable
+  end
  )
  (func $~start
   global.get $~started