Restructure ifs with a value (#1743)

We previously had code to recreate an if from a block+branch when possible, but not when the block had a return value. This PR adds support to restructure that too, into an if with a value.

2 files changed, 113 insertions, 0 deletions

diff --git a/test/passes/remove-unused-brs.txt b/test/passes/remove-unused-brs.txt
index b5bcce9f2..03eb7b716 100644
--- a/test/passes/remove-unused-brs.txt
+++ b/test/passes/remove-unused-brs.txt
@@ -1946,4 +1946,61 @@
    )
   )
  )
+ (func $drop-restructure-if (; 81 ;) (type $3) (param $x i32) (param $y i32) (result i32)
+  (if (result i32)
+   (get_local $y)
+   (get_local $x)
+   (block $label$2 (result i32)
+    (nop)
+    (i32.const 0)
+   )
+  )
+ )
+ (func $drop-restructure-if-final (; 82 ;) (type $3) (param $x i32) (param $y i32) (result i32)
+  (if (result i32)
+   (get_local $y)
+   (get_local $x)
+   (block $label$2 (result i32)
+    (nop)
+    (unreachable)
+   )
+  )
+ )
+ (func $drop-restructure-if-middle (; 83 ;) (type $3) (param $x i32) (param $y i32) (result i32)
+  (if (result i32)
+   (get_local $y)
+   (get_local $x)
+   (block $label$2 (result i32)
+    (nop)
+    (nop)
+    (i32.const 0)
+   )
+  )
+ )
+ (func $drop-restructure-if-bad (; 84 ;) (type $3) (param $x i32) (param $y i32) (result i32)
+  (block $label$2 (result i32)
+   (drop
+    (br_if $label$2
+     (tee_local $y
+      (get_local $x)
+     )
+     (get_local $y)
+    )
+   )
+   (i32.const 0)
+  )
+ )
+ (func $drop-restructure-if-bad-2 (; 85 ;) (type $3) (param $x i32) (param $y i32) (result i32)
+  (block $label$2 (result i32)
+   (drop
+    (br_if $label$2
+     (get_local $y)
+     (tee_local $y
+      (get_local $x)
+     )
+    )
+   )
+   (i32.const 0)
+  )
+ )
 )
diff --git a/test/passes/remove-unused-brs.wast b/test/passes/remove-unused-brs.wast
index 8325b47ac..7f77fd00c 100644
--- a/test/passes/remove-unused-brs.wast
+++ b/test/passes/remove-unused-brs.wast
@@ -1561,5 +1561,61 @@
     )
    )
   )
+  (func $drop-restructure-if (param $x i32) (param $y i32) (result i32)
+   (block $label$2 (result i32)
+    (drop
+     (br_if $label$2
+      (get_local $x)
+      (get_local $y)
+     )
+    )
+    (i32.const 0)
+   )
+  )
+  (func $drop-restructure-if-final (param $x i32) (param $y i32) (result i32)
+   (block $label$2 (result i32)
+    (drop
+     (br_if $label$2
+      (get_local $x)
+      (get_local $y)
+     )
+    )
+    (unreachable)
+   )
+  )
+  (func $drop-restructure-if-middle (param $x i32) (param $y i32) (result i32)
+   (block $label$2 (result i32)
+    (drop
+     (br_if $label$2
+      (get_local $x)
+      (get_local $y)
+     )
+    )
+    (nop) ;; the middle
+    (i32.const 0)
+   )
+  )
+  (func $drop-restructure-if-bad (param $x i32) (param $y i32) (result i32)
+   (block $label$2 (result i32)
+    (drop
+     (br_if $label$2
+      (tee_local $y (get_local $x))
+      (get_local $y)
+     )
+    )
+    (i32.const 0)
+   )
+  )
+  (func $drop-restructure-if-bad-2 (param $x i32) (param $y i32) (result i32)
+   (block $label$2 (result i32)
+    (drop
+     (br_if $label$2
+      (get_local $y)
+      (tee_local $y (get_local $x))
+     )
+    )
+    (i32.const 0)
+   )
+  )
 )