MergeBlocks: optimize If conditions (#4260)

Code in the If condition can be moved out to before the if.

Existing test updates are 99% whitespace.

5 files changed, 157 insertions, 124 deletions

diff --git a/src/passes/MergeBlocks.cpp b/src/passes/MergeBlocks.cpp
index b77dbef83..6ba486717 100644
--- a/src/passes/MergeBlocks.cpp
+++ b/src/passes/MergeBlocks.cpp
@@ -520,6 +520,11 @@ struct MergeBlocks
     }
   }
 
+  void visitIf(If* curr) {
+    // We can move code out of the condition, but not any of the other children.
+    optimize(curr, curr->condition);
+  }
+
   void optimizeTernary(Expression* curr,
                        Expression*& first,
                        Expression*& second,
diff --git a/test/lit/passes/inlining-optimizing_optimize-level=3.wast b/test/lit/passes/inlining-optimizing_optimize-level=3.wast
index 4a4f21f94..1ae11b22a 100644
--- a/test/lit/passes/inlining-optimizing_optimize-level=3.wast
+++ b/test/lit/passes/inlining-optimizing_optimize-level=3.wast
@@ -2584,79 +2584,77 @@
  ;; CHECK-NEXT:     )
  ;; CHECK-NEXT:    )
  ;; CHECK-NEXT:    (local.set $3
+ ;; CHECK-NEXT:     (i32.load8_s
+ ;; CHECK-NEXT:      (local.tee $4
+ ;; CHECK-NEXT:       (i32.add
+ ;; CHECK-NEXT:        (local.get $2)
+ ;; CHECK-NEXT:        (i32.const 74)
+ ;; CHECK-NEXT:       )
+ ;; CHECK-NEXT:      )
+ ;; CHECK-NEXT:     )
+ ;; CHECK-NEXT:    )
+ ;; CHECK-NEXT:    (i32.store8
+ ;; CHECK-NEXT:     (local.get $4)
+ ;; CHECK-NEXT:     (i32.or
+ ;; CHECK-NEXT:      (i32.add
+ ;; CHECK-NEXT:       (local.get $3)
+ ;; CHECK-NEXT:       (i32.const 255)
+ ;; CHECK-NEXT:      )
+ ;; CHECK-NEXT:      (local.get $3)
+ ;; CHECK-NEXT:     )
+ ;; CHECK-NEXT:    )
+ ;; CHECK-NEXT:    (local.set $3
  ;; CHECK-NEXT:     (if (result i32)
- ;; CHECK-NEXT:      (block (result i32)
- ;; CHECK-NEXT:       (local.set $3
- ;; CHECK-NEXT:        (i32.load8_s
- ;; CHECK-NEXT:         (local.tee $4
- ;; CHECK-NEXT:          (i32.add
- ;; CHECK-NEXT:           (local.get $2)
- ;; CHECK-NEXT:           (i32.const 74)
- ;; CHECK-NEXT:          )
+ ;; CHECK-NEXT:      (if (result i32)
+ ;; CHECK-NEXT:       (i32.and
+ ;; CHECK-NEXT:        (local.tee $3
+ ;; CHECK-NEXT:         (i32.load
+ ;; CHECK-NEXT:          (local.get $2)
  ;; CHECK-NEXT:         )
  ;; CHECK-NEXT:        )
+ ;; CHECK-NEXT:        (i32.const 8)
  ;; CHECK-NEXT:       )
- ;; CHECK-NEXT:       (i32.store8
- ;; CHECK-NEXT:        (local.get $4)
- ;; CHECK-NEXT:        (i32.or
- ;; CHECK-NEXT:         (i32.add
+ ;; CHECK-NEXT:       (block (result i32)
+ ;; CHECK-NEXT:        (i32.store
+ ;; CHECK-NEXT:         (local.get $2)
+ ;; CHECK-NEXT:         (i32.or
  ;; CHECK-NEXT:          (local.get $3)
- ;; CHECK-NEXT:          (i32.const 255)
+ ;; CHECK-NEXT:          (i32.const 32)
  ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (local.get $3)
  ;; CHECK-NEXT:        )
+ ;; CHECK-NEXT:        (i32.const -1)
  ;; CHECK-NEXT:       )
- ;; CHECK-NEXT:       (if (result i32)
- ;; CHECK-NEXT:        (i32.and
+ ;; CHECK-NEXT:       (block (result i32)
+ ;; CHECK-NEXT:        (i32.store offset=8
+ ;; CHECK-NEXT:         (local.get $2)
+ ;; CHECK-NEXT:         (i32.const 0)
+ ;; CHECK-NEXT:        )
+ ;; CHECK-NEXT:        (i32.store offset=4
+ ;; CHECK-NEXT:         (local.get $2)
+ ;; CHECK-NEXT:         (i32.const 0)
+ ;; CHECK-NEXT:        )
+ ;; CHECK-NEXT:        (i32.store offset=28
+ ;; CHECK-NEXT:         (local.get $2)
  ;; CHECK-NEXT:         (local.tee $3
- ;; CHECK-NEXT:          (i32.load
+ ;; CHECK-NEXT:          (i32.load offset=44
  ;; CHECK-NEXT:           (local.get $2)
  ;; CHECK-NEXT:          )
  ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (i32.const 8)
  ;; CHECK-NEXT:        )
- ;; CHECK-NEXT:        (block (result i32)
- ;; CHECK-NEXT:         (i32.store
- ;; CHECK-NEXT:          (local.get $2)
- ;; CHECK-NEXT:          (i32.or
- ;; CHECK-NEXT:           (local.get $3)
- ;; CHECK-NEXT:           (i32.const 32)
- ;; CHECK-NEXT:          )
- ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (i32.const -1)
+ ;; CHECK-NEXT:        (i32.store offset=20
+ ;; CHECK-NEXT:         (local.get $2)
+ ;; CHECK-NEXT:         (local.get $3)
  ;; CHECK-NEXT:        )
- ;; CHECK-NEXT:        (block (result i32)
- ;; CHECK-NEXT:         (i32.store offset=8
- ;; CHECK-NEXT:          (local.get $2)
- ;; CHECK-NEXT:          (i32.const 0)
- ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (i32.store offset=4
- ;; CHECK-NEXT:          (local.get $2)
- ;; CHECK-NEXT:          (i32.const 0)
- ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (i32.store offset=28
- ;; CHECK-NEXT:          (local.get $2)
- ;; CHECK-NEXT:          (local.tee $3
- ;; CHECK-NEXT:           (i32.load offset=44
- ;; CHECK-NEXT:            (local.get $2)
- ;; CHECK-NEXT:           )
- ;; CHECK-NEXT:          )
- ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (i32.store offset=20
- ;; CHECK-NEXT:          (local.get $2)
+ ;; CHECK-NEXT:        (i32.store offset=16
+ ;; CHECK-NEXT:         (local.get $2)
+ ;; CHECK-NEXT:         (i32.add
  ;; CHECK-NEXT:          (local.get $3)
- ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (i32.store offset=16
- ;; CHECK-NEXT:          (local.get $2)
- ;; CHECK-NEXT:          (i32.add
- ;; CHECK-NEXT:           (local.get $3)
- ;; CHECK-NEXT:           (i32.load offset=48
- ;; CHECK-NEXT:            (local.get $2)
- ;; CHECK-NEXT:           )
+ ;; CHECK-NEXT:          (i32.load offset=48
+ ;; CHECK-NEXT:           (local.get $2)
  ;; CHECK-NEXT:          )
  ;; CHECK-NEXT:         )
- ;; CHECK-NEXT:         (i32.const 0)
  ;; CHECK-NEXT:        )
+ ;; CHECK-NEXT:        (i32.const 0)
  ;; CHECK-NEXT:       )
  ;; CHECK-NEXT:      )
  ;; CHECK-NEXT:      (i32.const 0)
diff --git a/test/lit/passes/merge-blocks.wast b/test/lit/passes/merge-blocks.wast
index e6136d4da..3d931690b 100644
--- a/test/lit/passes/merge-blocks.wast
+++ b/test/lit/passes/merge-blocks.wast
@@ -188,4 +188,42 @@
    )
   )
  )
+
+ ;; CHECK:      (func $if-condition (result i32)
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (i32.const 0)
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT:  (if (result i32)
+ ;; CHECK-NEXT:   (i32.const 1)
+ ;; CHECK-NEXT:   (block (result i32)
+ ;; CHECK-NEXT:    (drop
+ ;; CHECK-NEXT:     (i32.const 2)
+ ;; CHECK-NEXT:    )
+ ;; CHECK-NEXT:    (i32.const 3)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:   (block (result i32)
+ ;; CHECK-NEXT:    (drop
+ ;; CHECK-NEXT:     (i32.const 4)
+ ;; CHECK-NEXT:    )
+ ;; CHECK-NEXT:    (i32.const 5)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $if-condition (result i32)
+  ;; Content can be moved out of an if condition, but not anywhere else.
+  (if (result i32)
+   (block (result i32)
+    (drop (i32.const 0))
+    (i32.const 1)
+   )
+   (block (result i32)
+    (drop (i32.const 2))
+    (i32.const 3)
+   )
+   (block (result i32)
+    (drop (i32.const 4))
+    (i32.const 5)
+   )
+  )
+ )
 )
diff --git a/test/passes/converge_O3_metrics.bin.txt b/test/passes/converge_O3_metrics.bin.txt
index 5c41b3146..bf24bb5e2 100644
--- a/test/passes/converge_O3_metrics.bin.txt
+++ b/test/passes/converge_O3_metrics.bin.txt
@@ -7,10 +7,10 @@ total
  [table-data]   : 429     
  [tables]       : 0       
  [tags]         : 0       
- [total]        : 553     
+ [total]        : 552     
  [vars]         : 2       
  Binary         : 12      
- Block          : 7       
+ Block          : 6       
  Break          : 3       
  Call           : 1       
  CallIndirect   : 4       
@@ -69,28 +69,26 @@ total
     )
    )
   )
-  (if
-   (block (result i32)
-    (local.set $0
-     (i32.const 10888)
-    )
-    (loop $label$3
-     (br_if $label$3
-      (i32.load8_s
-       (local.tee $0
-        (i32.add
-         (local.get $0)
-         (i32.const 1)
-        )
-       )
+  (local.set $0
+   (i32.const 10888)
+  )
+  (loop $label$3
+   (br_if $label$3
+    (i32.load8_s
+     (local.tee $0
+      (i32.add
+       (local.get $0)
+       (i32.const 1)
       )
      )
     )
-    (local.tee $0
-     (i32.sub
-      (local.get $0)
-      (i32.const 10888)
-     )
+   )
+  )
+  (if
+   (local.tee $0
+    (i32.sub
+     (local.get $0)
+     (i32.const 10888)
     )
    )
    (block $label$2
@@ -237,10 +235,10 @@ total
  [table-data]   : 429     
  [tables]       : 0       
  [tags]         : 0       
- [total]        : 549           -4
+ [total]        : 548           -4
  [vars]         : 2       
  Binary         : 12      
- Block          : 7       
+ Block          : 6       
  Break          : 3       
  Call           : 1       
  CallIndirect   : 4       
@@ -297,28 +295,26 @@ total
     )
    )
   )
-  (if
-   (block (result i32)
-    (local.set $0
-     (i32.const 10888)
-    )
-    (loop $label$3
-     (br_if $label$3
-      (i32.load8_s
-       (local.tee $0
-        (i32.add
-         (local.get $0)
-         (i32.const 1)
-        )
-       )
+  (local.set $0
+   (i32.const 10888)
+  )
+  (loop $label$3
+   (br_if $label$3
+    (i32.load8_s
+     (local.tee $0
+      (i32.add
+       (local.get $0)
+       (i32.const 1)
       )
      )
     )
-    (local.tee $0
-     (i32.sub
-      (local.get $0)
-      (i32.const 10888)
-     )
+   )
+  )
+  (if
+   (local.tee $0
+    (i32.sub
+     (local.get $0)
+     (i32.const 10888)
     )
    )
    (block $label$2
@@ -460,10 +456,10 @@ total
  [table-data]   : 429     
  [tables]       : 0       
  [tags]         : 0       
- [total]        : 549     
+ [total]        : 548     
  [vars]         : 2       
  Binary         : 12      
- Block          : 7       
+ Block          : 6       
  Break          : 3       
  Call           : 1       
  CallIndirect   : 4       
@@ -520,28 +516,26 @@ total
     )
    )
   )
-  (if
-   (block (result i32)
-    (local.set $0
-     (i32.const 10888)
-    )
-    (loop $label$3
-     (br_if $label$3
-      (i32.load8_s
-       (local.tee $0
-        (i32.add
-         (local.get $0)
-         (i32.const 1)
-        )
-       )
+  (local.set $0
+   (i32.const 10888)
+  )
+  (loop $label$3
+   (br_if $label$3
+    (i32.load8_s
+     (local.tee $0
+      (i32.add
+       (local.get $0)
+       (i32.const 1)
       )
      )
     )
-    (local.tee $0
-     (i32.sub
-      (local.get $0)
-      (i32.const 10888)
-     )
+   )
+  )
+  (if
+   (local.tee $0
+    (i32.sub
+     (local.get $0)
+     (i32.const 10888)
     )
    )
    (block $label$2
diff --git a/test/passes/remove-unused-names_merge-blocks_all-features.txt b/test/passes/remove-unused-names_merge-blocks_all-features.txt
index 9f15d1319..ab1837ef7 100644
--- a/test/passes/remove-unused-names_merge-blocks_all-features.txt
+++ b/test/passes/remove-unused-names_merge-blocks_all-features.txt
@@ -775,13 +775,11 @@
  (func $block-type-change
   (local $0 f64)
   (local $1 f64)
+  (nop)
   (if
-   (block (result i32)
-    (nop)
-    (f64.gt
-     (local.get $0)
-     (local.get $1)
-    )
+   (f64.gt
+    (local.get $0)
+    (local.get $1)
    )
    (nop)
   )