Speculate in simplify-locals that it is worth turning an if into

an if-else.

If an if sets a local,

  (if
    (..condition..)
    (set_local $x (..value..))
  )

we can turn it into

  (set_local $x
    (if
      (..condition..)
      (..value..)
      (get_local $x)
    )
  )

This increases code size and adds a branch in the if, but allows
the set to be optimized into a tee or optimized out entirely. In
the worst case, other optimizations can break up an if with a copy
in one of its arms later.

Includes a determinism fix for EquivalentSets, which this patch
triggered.

1 files changed, 22 insertions, 27 deletions

diff --git a/test/debugInfo.fromasm.imprecise b/test/debugInfo.fromasm.imprecise
index f8734889f..b4d624e89 100644
--- a/test/debugInfo.fromasm.imprecise
+++ b/test/debugInfo.fromasm.imprecise
@@ -118,41 +118,36 @@
   (set_local $1
    (block $__rjto$0 (result i32)
     (block $__rjti$0
-     (br $__rjto$0
-      (if (result i32)
-       (i32.lt_s
-        (tee_local $1
-         (i32.add
-          (get_local $0)
-          (i32.const 52)
-         )
+     (if
+      (i32.lt_s
+       (tee_local $1
+        (i32.add
+         (get_local $0)
+         (i32.const 52)
         )
-        (i32.const 1369188723)
        )
-       (block (result i32)
-        (br_if $__rjti$0
-         (i32.eqz
-          (i32.sub
-           (get_local $1)
-           (i32.const -1108210269)
-          )
-         )
+       (i32.const 1369188723)
+      )
+      (br_if $__rjti$0
+       (i32.eqz
+        (i32.sub
+         (get_local $1)
+         (i32.const -1108210269)
         )
-        (i32.const 0)
        )
-       (block (result i32)
-        (br_if $__rjti$0
-         (i32.eqz
-          (i32.sub
-           (get_local $1)
-           (i32.const 1369188723)
-          )
-         )
+      )
+      (br_if $__rjti$0
+       (i32.eqz
+        (i32.sub
+         (get_local $1)
+         (i32.const 1369188723)
         )
-        (i32.const 0)
        )
       )
      )
+     (br $__rjto$0
+      (i32.const 0)
+     )
     )
     (call $switch_reach
      (get_local $0)