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, 72 insertions, 40 deletions

diff --git a/test/lit/passes/optimize-stack-ir.wast b/test/lit/passes/optimize-stack-ir.wast
index adb787879..bb1e0f9f0 100644
--- a/test/lit/passes/optimize-stack-ir.wast
+++ b/test/lit/passes/optimize-stack-ir.wast
@@ -159,8 +159,10 @@
           )
           (i32.const 0)
         )
-        (br $topmost
-          (f64.const -3.4)
+        (then
+          (br $topmost
+            (f64.const -3.4)
+          )
         )
       )
       (if
@@ -170,8 +172,10 @@
           )
           (f64.const 0)
         )
-        (br $topmost
-          (f64.const 5.6)
+        (then
+          (br $topmost
+            (f64.const 5.6)
+          )
         )
       )
       (f64.const 1.2)
@@ -224,8 +228,10 @@
           (local.get $x)
           (f64.const 0)
         )
-        (br $topmost
-          (f64.const 1.2)
+        (then
+          (br $topmost
+            (f64.const 1.2)
+          )
         )
       )
       (if
@@ -233,8 +239,10 @@
           (local.get $Int)
           (f64.const 0)
         )
-        (br $topmost
-          (f64.const -3.4)
+        (then
+          (br $topmost
+            (f64.const -3.4)
+          )
         )
       )
       (if
@@ -242,8 +250,10 @@
           (local.get $Double)
           (i32.const 0)
         )
-        (br $topmost
-          (f64.const 5.6)
+        (then
+          (br $topmost
+            (f64.const 5.6)
+          )
         )
       )
       (if
@@ -251,8 +261,10 @@
           (local.get $x)
           (local.get $y)
         )
-        (br $topmost
-          (local.get $x)
+        (then
+          (br $topmost
+            (local.get $x)
+          )
         )
       )
       (local.get $y)
@@ -899,8 +911,12 @@
     (f64.abs
       (if ;; note no type - valid in binaryen IR, in wasm must be i32
         (i32.const 3)
-        (return (i32.const 2))
-        (return (i32.const 1))
+        (then
+          (return (i32.const 2))
+        )
+        (else
+          (return (i32.const 1))
+        )
       )
     )
   )
@@ -919,8 +935,12 @@
   (func $unreachable-if-toplevel (result i32)
     (if ;; note no type - valid in binaryen IR, in wasm must be i32
       (i32.const 3)
-      (return (i32.const 2))
-      (return (i32.const 1))
+      (then
+        (return (i32.const 2))
+      )
+      (else
+        (return (i32.const 1))
+      )
     )
   )
 
@@ -986,16 +1006,16 @@
   ;; CHECK-NEXT:  unreachable
   ;; CHECK-NEXT: )
   (func $unreachable-ifs
-    (if (unreachable) (nop))
-    (if (unreachable) (unreachable))
-    (if (unreachable) (nop) (nop))
-    (if (unreachable) (unreachable) (nop))
-    (if (unreachable) (nop) (unreachable))
-    (if (unreachable) (unreachable) (unreachable))
+    (if (unreachable) (then (nop)))
+    (if (unreachable) (then (unreachable)))
+    (if (unreachable) (then (nop) )(else (nop)))
+    (if (unreachable) (then (unreachable) )(else (nop)))
+    (if (unreachable) (then (nop) )(else (unreachable)))
+    (if (unreachable) (then (unreachable) )(else (unreachable)))
     ;;
-    (if (i32.const 1) (unreachable) (nop))
-    (if (i32.const 1) (nop) (unreachable))
-    (if (i32.const 1) (unreachable) (unreachable))
+    (if (i32.const 1) (then (unreachable) )(else (nop)))
+    (if (i32.const 1) (then (nop) )(else (unreachable)))
+    (if (i32.const 1) (then (unreachable) )(else (unreachable)))
   )
 
   ;; CHECK:      (func $unreachable-if-arm (type $FUNCSIG$v)
@@ -1008,13 +1028,17 @@
   (func $unreachable-if-arm
     (if
       (i32.const 1)
-      (block
-        (nop)
+      (then
+        (block
+          (nop)
+        )
       )
-      (block
-        (unreachable)
-        (drop
-          (i32.const 1)
+      (else
+        (block
+          (unreachable)
+          (drop
+            (i32.const 1)
+          )
         )
       )
     )
@@ -1137,8 +1161,12 @@
   (func $local-to-stack-3-no (param $x i32) (result i32)
     (local $temp i32)
     (if (i32.const 1)
-      (local.set $temp (call $local-to-stack (i32.const 1)))
-      (local.set $temp (call $local-to-stack (i32.const 2))) ;; two sets for that get
+      (then
+        (local.set $temp (call $local-to-stack (i32.const 1)))
+      )
+      (else
+        (local.set $temp (call $local-to-stack (i32.const 2))) ;; two sets for that get
+      )
     )
     (drop (call $local-to-stack (i32.const 3)))
     (local.get $temp)
@@ -1338,7 +1366,7 @@
     (local $temp2 i32)
     (local.set $temp2 (call $local-to-stack-multi-4 (i32.const 0)))
     (local.set $temp1 (call $local-to-stack-multi-4 (i32.const 1)))
-    (if (i32.const 0) (nop))
+    (if (i32.const 0) (then (nop)))
     (drop (local.get $temp1))
     (local.set $temp1 (call $local-to-stack-multi-4 (i32.const 2)))
     (block $block (br $block))
@@ -1362,13 +1390,17 @@
   (func $local-to-stack-in-control-flow
     (local $temp1 i32)
     (if (i32.const 0)
-      (block
-        (local.set $temp1 (call $local-to-stack-multi-4 (i32.const 0)))
-        (drop (local.get $temp1))
+      (then
+        (block
+          (local.set $temp1 (call $local-to-stack-multi-4 (i32.const 0)))
+          (drop (local.get $temp1))
+        )
       )
-      (block
-        (local.set $temp1 (call $local-to-stack-multi-4 (i32.const 1)))
-        (drop (local.get $temp1))
+      (else
+        (block
+          (local.set $temp1 (call $local-to-stack-multi-4 (i32.const 1)))
+          (drop (local.get $temp1))
+        )
       )
     )
   )