Require `then` and `else` with `if` (#6201)

We previously supported (and primarily used) a non-standard text format for
conditionals in which the condition, if-true expression, and if-false expression
were all simply s-expression children of the `if` expression. The standard text
format, however, requires the use of `then` and `else` forms to introduce the
if-true and if-false arms of the conditional. Update the legacy text parser to
require the standard format and update all tests to match. Update the printer to
print the standard format as well.

The .wast and .wat test inputs were mechanically updated with this script:
https://gist.github.com/tlively/85ae7f01f92f772241ec994c840ccbb1

1 files changed, 20 insertions, 14 deletions

diff --git a/test/lit/passes/simplify-globals-dominance.wast b/test/lit/passes/simplify-globals-dominance.wast
index 3756a4a7e..dddcaa983 100644
--- a/test/lit/passes/simplify-globals-dominance.wast
+++ b/test/lit/passes/simplify-globals-dominance.wast
@@ -14,7 +14,7 @@
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT:  (if
   ;; CHECK-NEXT:   (i32.const 0)
-  ;; CHECK-NEXT:   (block
+  ;; CHECK-NEXT:   (then
   ;; CHECK-NEXT:    (drop
   ;; CHECK-NEXT:     (i32.const 10)
   ;; CHECK-NEXT:    )
@@ -23,8 +23,10 @@
   ;; CHECK-NEXT:     (global.get $global)
   ;; CHECK-NEXT:    )
   ;; CHECK-NEXT:   )
-  ;; CHECK-NEXT:   (drop
-  ;; CHECK-NEXT:    (global.get $global)
+  ;; CHECK-NEXT:   (else
+  ;; CHECK-NEXT:    (drop
+  ;; CHECK-NEXT:     (global.get $global)
+  ;; CHECK-NEXT:    )
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT: )
@@ -34,22 +36,26 @@
     )
     (if
       (i32.const 0)
-      (block
-        ;; This is dominated by the set, so we can apply 10 here.
-        (drop
-          (global.get $global)
+      (then
+        (block
+          ;; This is dominated by the set, so we can apply 10 here.
+          (drop
+            (global.get $global)
+          )
+          (call $test)
+          ;; This is after a call, so we do nothing (we are still dominated by the
+          ;; global.set, but the call might set the global to another value).
+          (drop
+            (global.get $global)
+          )
         )
-        (call $test)
-        ;; This is after a call, so we do nothing (we are still dominated by the
-        ;; global.set, but the call might set the global to another value).
+      )
+      ;; This is dominated by the set, but we do not optimize it yet. TODO
+      (else
         (drop
           (global.get $global)
         )
       )
-      ;; This is dominated by the set, but we do not optimize it yet. TODO
-      (drop
-        (global.get $global)
-      )
     )
   )
 )