[Selectify] Increase TooCostlyToRunUnconditionally from 7 to 9 (#4228)

This makes Binaryen match LLVM on a real-world case, which is probably
the safest heuristic to use.

3 files changed, 59 insertions, 9 deletions

diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
index cbad81247..01c465f18 100644
--- a/src/passes/RemoveUnusedBrs.cpp
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -80,7 +80,10 @@ static bool canTurnIfIntoBrIf(Expression* ifCondition,
   return !EffectAnalyzer(options, wasm, ifCondition).invalidates(value);
 }
 
-const Index TooCostlyToRunUnconditionally = 7;
+// This leads to similar choices as LLVM does.
+// See https://github.com/WebAssembly/binaryen/pull/4228
+// It can be tuned more later.
+const Index TooCostlyToRunUnconditionally = 9;
 
 // Check if it is not worth it to run code unconditionally. This
 // assumes we are trying to run two expressions where previously
diff --git a/test/lit/passes/remove-unused-brs.wast b/test/lit/passes/remove-unused-brs.wast
index e5b29d2e6..3c5d49988 100644
--- a/test/lit/passes/remove-unused-brs.wast
+++ b/test/lit/passes/remove-unused-brs.wast
@@ -29,6 +29,51 @@
     )
   )
 
+  ;; CHECK:      (func $selectify-simple (param $0 i32) (result i32)
+  ;; CHECK-NEXT:  (select
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:   (i32.lt_u
+  ;; CHECK-NEXT:    (i32.sub
+  ;; CHECK-NEXT:     (i32.or
+  ;; CHECK-NEXT:      (local.get $0)
+  ;; CHECK-NEXT:      (i32.const 32)
+  ;; CHECK-NEXT:     )
+  ;; CHECK-NEXT:     (i32.const 97)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (i32.const 6)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (i32.lt_u
+  ;; CHECK-NEXT:    (i32.sub
+  ;; CHECK-NEXT:     (local.get $0)
+  ;; CHECK-NEXT:     (i32.const 48)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (i32.const 10)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $selectify-simple (param $0 i32) (result i32)
+    (if (result i32)
+      (i32.lt_u
+        (i32.sub
+          (local.get $0)
+          (i32.const 48)
+        )
+        (i32.const 10)
+      )
+      (i32.const 1)
+      (i32.lt_u
+        (i32.sub
+          (i32.or
+            (local.get $0)
+            (i32.const 32)
+          )
+          (i32.const 97)
+        )
+        (i32.const 6)
+      )
+    )
+  )
+
   ;; CHECK:      (func $restructure-br_if (param $x i32) (result i32)
   ;; CHECK-NEXT:  (if (result i32)
   ;; CHECK-NEXT:   (local.get $x)
@@ -410,7 +455,9 @@
   ;; CHECK-NEXT:         (i32.eqz
   ;; CHECK-NEXT:          (i32.eqz
   ;; CHECK-NEXT:           (i32.eqz
-  ;; CHECK-NEXT:            (local.get $x)
+  ;; CHECK-NEXT:            (i32.eqz
+  ;; CHECK-NEXT:             (local.get $x)
+  ;; CHECK-NEXT:            )
   ;; CHECK-NEXT:           )
   ;; CHECK-NEXT:          )
   ;; CHECK-NEXT:         )
@@ -432,9 +479,9 @@
         (i32.const 1)
       )
       (if
-        (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz
+        (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz (i32.eqz
           (local.get $x)
-        ))))))))
+        )))))))))
         (call $if-of-if-but-too-costly)
       )
     )
diff --git a/test/passes/remove-unused-brs_enable-multivalue.txt b/test/passes/remove-unused-brs_enable-multivalue.txt
index 46938f784..cf8ad7ec2 100644
--- a/test/passes/remove-unused-brs_enable-multivalue.txt
+++ b/test/passes/remove-unused-brs_enable-multivalue.txt
@@ -2355,11 +2355,7 @@
  )
  (func $selectify (param $x i32)
   (drop
-   (if (result i32)
-    (i32.eq
-     (local.get $x)
-     (i32.const 1)
-    )
+   (select
     (i32.mul
      (i32.const 2)
      (i32.const 3)
@@ -2368,6 +2364,10 @@
      (i32.const 2)
      (i32.const 3)
     )
+    (i32.eq
+     (local.get $x)
+     (i32.const 1)
+    )
    )
   )
   (drop