Improve selectification in remove-unused-brs

We turned an if into a select when optimizing for size (and if
side effects etc. allow so). This patch improves that, doing it
not just when optimizing for size, but also when it looks
beneficial given the amount of work on both sides of the if. As
a result we can create selects in -O3 etc.

5 files changed, 89 insertions, 52 deletions

diff --git a/test/binaryen.js/optimize-levels.js.txt b/test/binaryen.js/optimize-levels.js.txt
index 8cb0dfea5..5381722c0 100644
--- a/test/binaryen.js/optimize-levels.js.txt
+++ b/test/binaryen.js/optimize-levels.js.txt
@@ -52,10 +52,10 @@ shrinkLevel=0
  (type $i (func (param i32) (result i32)))
  (export "test" (func $test))
  (func $test (; 0 ;) (type $i) (param $0 i32) (result i32)
-  (if (result i32)
-   (get_local $0)
+  (select
    (get_local $0)
    (i32.const 0)
+   (get_local $0)
   )
  )
 )
diff --git a/test/passes/1.txt b/test/passes/1.txt
index 7b6f4f249..0a7716a23 100644
--- a/test/passes/1.txt
+++ b/test/passes/1.txt
@@ -19,15 +19,15 @@
  (func $ifs (; 4 ;) (type $2) (param $0 i32) (result i32)
   (if (result i32)
    (get_local $0)
-   (if (result i32)
-    (get_local $0)
+   (select
     (i32.const 2)
     (i32.const 3)
-   )
-   (if (result i32)
     (get_local $0)
+   )
+   (select
     (i32.const 4)
     (i32.const 5)
+    (get_local $0)
    )
   )
  )
diff --git a/test/passes/O.txt b/test/passes/O.txt
index 3ba18693f..ca6a7f81f 100644
--- a/test/passes/O.txt
+++ b/test/passes/O.txt
@@ -1,8 +1,10 @@
 (module
  (type $0 (func (result i32)))
  (type $1 (func (param i64)))
+ (type $2 (func (param i32) (result i32)))
  (export "ret" (func $ret))
  (export "waka" (func $if-0-unreachable-to-none))
+ (export "many-selects" (func $many-selects))
  (func $ret (; 0 ;) (; has Stack IR ;) (type $0) (result i32)
   (drop
    (call $ret)
@@ -18,4 +20,23 @@
  (func $if-0-unreachable-to-none (; 1 ;) (; has Stack IR ;) (type $1) (param $0 i64)
   (unreachable)
  )
+ (func $many-selects (; 2 ;) (; has Stack IR ;) (type $2) (param $0 i32) (result i32)
+  (tee_local $0
+   (select
+    (i32.const -1073741824)
+    (select
+     (i32.const 1073741823)
+     (get_local $0)
+     (i32.gt_s
+      (get_local $0)
+      (i32.const 1073741823)
+     )
+    )
+    (i32.lt_s
+     (get_local $0)
+     (i32.const -1073741824)
+    )
+   )
+  )
+ )
 )
diff --git a/test/passes/O.wast b/test/passes/O.wast
index e42541376..e183e02c1 100644
--- a/test/passes/O.wast
+++ b/test/passes/O.wast
@@ -24,5 +24,26 @@
     )
    )
   )
+  (func $many-selects (export "many-selects") (param $0 i32) (result i32)
+   (if
+    (i32.lt_s
+     (get_local $0)
+     (i32.const -1073741824)
+    )
+    (set_local $0
+     (i32.const -1073741824)
+    )
+    (if
+     (i32.gt_s
+      (get_local $0)
+      (i32.const 1073741823)
+     )
+     (set_local $0
+      (i32.const 1073741823)
+     )
+    )
+   )
+   (get_local $0)
+  )
 )
 
diff --git a/test/passes/remove-unused-brs.txt b/test/passes/remove-unused-brs.txt
index 19773b7f6..daa7eca3c 100644
--- a/test/passes/remove-unused-brs.txt
+++ b/test/passes/remove-unused-brs.txt
@@ -179,8 +179,7 @@
   )
  )
  (func $b14 (; 14 ;) (type $2) (result i32)
-  (if (result i32)
-   (i32.const 1)
+  (select
    (block $topmost (result i32)
     (block $block1 (result i32)
      (i32.const 12)
@@ -189,6 +188,7 @@
    (block $block3 (result i32)
     (i32.const 27)
    )
+   (i32.const 1)
   )
  )
  (func $b15 (; 15 ;) (type $1)
@@ -726,10 +726,10 @@
      (i32.const 6)
     )
    )
-   (if (result i32)
-    (i32.const 6)
+   (select
     (i32.const 7)
     (i32.const 8)
+    (i32.const 6)
    )
   )
  )
@@ -1861,10 +1861,10 @@
   (i32.const 0)
  )
  (func $if-flow-1 (; 75 ;) (type $2) (result i32)
-  (if (result i32)
-   (i32.const 0)
+  (select
    (i32.const 1)
    (i32.const 2)
+   (i32.const 0)
   )
  )
  (func $if-flow-2 (; 76 ;) (type $2) (result i32)
@@ -2073,12 +2073,12 @@
   )
  )
  (func $if-block-br-5-value (; 93 ;) (type $2) (result i32)
-  (if (result i32)
-   (i32.const 1)
+  (select
    (block $label (result i32)
     (i32.const 2)
    )
    (i32.const 3)
+   (i32.const 1)
   )
  )
  (func $restructure-if-outerType-change (; 94 ;) (type $1)
@@ -2249,11 +2249,7 @@
    )
   )
   (drop
-   (if (result i32)
-    (i32.eq
-     (get_local $x)
-     (i32.const 1)
-    )
+   (select
     (i32.add
      (i32.const 2)
      (i32.const 3)
@@ -2262,27 +2258,31 @@
      (i32.const 2)
      (i32.const 3)
     )
+    (i32.eq
+     (get_local $x)
+     (i32.const 1)
+    )
    )
   )
  )
  (func $if-one-side (; 103 ;) (type $2) (result i32)
   (local $x i32)
-  (if
-   (i32.const 1)
-   (set_local $x
+  (set_local $x
+   (select
     (i32.const 2)
+    (get_local $x)
+    (i32.const 1)
    )
   )
   (get_local $x)
  )
  (func $if-one-side-b (; 104 ;) (type $2) (result i32)
   (local $x i32)
-  (if
-   (i32.eqz
-    (i32.const 1)
-   )
-   (set_local $x
+  (set_local $x
+   (select
+    (get_local $x)
     (i32.const 2)
+    (i32.const 1)
    )
   )
   (get_local $x)
@@ -2297,14 +2297,12 @@
   (local $z i32)
   (drop
    (call $if-one-side-tee-etc
-    (block (result i32)
-     (if
+    (tee_local $x
+     (select
+      (i32.const -4)
+      (get_local $x)
       (i32.const -3)
-      (set_local $x
-       (i32.const -4)
-      )
      )
-     (get_local $x)
     )
    )
   )
@@ -2313,13 +2311,15 @@
  (func $ifs-copies-recursive (; 106 ;) (type $10) (param $20 i32) (result i32)
   (if
    (i32.const 1)
-   (if
-    (i32.const 2)
-    (if
-     (i32.const 3)
-     (set_local $20
+   (set_local $20
+    (select
+     (select
       (i32.const 4)
+      (get_local $20)
+      (i32.const 3)
      )
+     (get_local $20)
+     (i32.const 2)
     )
    )
   )
@@ -2329,12 +2329,11 @@
   (local $x i32)
   (local $y i32)
   (loop $top
-   (if
-    (i32.eqz
-     (i32.const 1)
-    )
-    (set_local $x
+   (set_local $x
+    (select
+     (get_local $x)
      (get_local $y)
+     (i32.const 1)
     )
    )
    (br $top)
@@ -2372,16 +2371,12 @@
   (local $y i32)
   (loop $top
    (drop
-    (block (result i32)
-     (if
-      (i32.eqz
-       (i32.const 1)
-      )
-      (set_local $x
-       (i32.const 2)
-      )
+    (tee_local $x
+     (select
+      (get_local $x)
+      (i32.const 2)
+      (i32.const 1)
      )
-     (get_local $x)
     )
    )
    (br $top)