Asyncify liveness analysis (#2890)

This finds out which locals are live at call sites that might pause/resume,
which is the set of locals we need to actually save/load. That is, if a local
is not alive at any call site in the function, then it's value doesn't need to
stay alive while sleeping.

This saves about 10% of locals that are saved/loaded, and about 1.5%
in final code size.

1 files changed, 3 insertions, 21 deletions

diff --git a/test/passes/asyncify_pass-arg=asyncify-ignore-indirect.txt b/test/passes/asyncify_pass-arg=asyncify-ignore-indirect.txt
index a48f3b3eb..690c96030 100644
--- a/test/passes/asyncify_pass-arg=asyncify-ignore-indirect.txt
+++ b/test/passes/asyncify_pass-arg=asyncify-ignore-indirect.txt
@@ -267,7 +267,7 @@
       (i32.load
        (global.get $__asyncify_data)
       )
-      (i32.const -12)
+      (i32.const -4)
      )
     )
     (local.set $5
@@ -275,18 +275,8 @@
       (global.get $__asyncify_data)
      )
     )
-    (local.set $x
-     (i32.load
-      (local.get $5)
-     )
-    )
-    (local.set $1
-     (i32.load offset=4
-      (local.get $5)
-     )
-    )
     (local.set $2
-     (i32.load offset=8
+     (i32.load
       (local.get $5)
      )
     )
@@ -446,14 +436,6 @@
    )
    (i32.store
     (local.get $6)
-    (local.get $x)
-   )
-   (i32.store offset=4
-    (local.get $6)
-    (local.get $1)
-   )
-   (i32.store offset=8
-    (local.get $6)
     (local.get $2)
    )
    (i32.store
@@ -462,7 +444,7 @@
      (i32.load
       (global.get $__asyncify_data)
      )
-     (i32.const 12)
+     (i32.const 4)
     )
    )
   )