Canonicalize subtraction with constant on the right to addition (#3321)

Using addition in more places is better for gzip, and helps simplify the
optimizer as well.

Add a FinalOptimizer phase to do optimizations like our signed LEB tweaks, to
reduce binary size in the rare case when we do want a subtraction.

1 files changed, 15 insertions, 15 deletions

diff --git a/test/passes/optimize-instructions_all-features.txt b/test/passes/optimize-instructions_all-features.txt
index 4a58c210f..a5cc470fb 100644
--- a/test/passes/optimize-instructions_all-features.txt
+++ b/test/passes/optimize-instructions_all-features.txt
@@ -818,16 +818,16 @@
    (local.get $0)
   )
   (i32.store offset=2
-   (i32.add
+   (i32.sub
     (local.get $0)
-    (i32.const -11)
+    (i32.const 11)
    )
    (local.get $0)
   )
   (i32.store offset=2
-   (i32.add
+   (i32.sub
     (local.get $0)
-    (i32.const -13)
+    (i32.const 13)
    )
    (local.get $0)
   )
@@ -1369,12 +1369,12 @@
    )
   )
   (drop
-   (i32.add
+   (i32.sub
     (i32.shl
      (local.get $1)
      (i32.const 3)
     )
-    (i32.const -66)
+    (i32.const 66)
    )
   )
   (drop
@@ -2529,25 +2529,25 @@
   )
  )
  (func $optimizeAddedConstants-filters-through-nonzero (result i32)
-  (i32.add
+  (i32.sub
    (i32.shl
     (i32.const -536870912)
     (i32.wrap_i64
      (i64.const 0)
     )
    )
-   (i32.const -31744)
+   (i32.const 31744)
   )
  )
  (func $optimizeAddedConstants-filters-through-nonzero-b (result i32)
-  (i32.add
+  (i32.sub
    (i32.shl
     (i32.const -536870912)
     (i32.wrap_i64
      (i64.const -1)
     )
    )
-   (i32.const -31744)
+   (i32.const 31744)
   )
  )
  (func $return-proper-value-from-shift-left-by-zero (result i32)
@@ -3424,7 +3424,7 @@
   )
   (drop
    (i32.eq
-    (i32.sub
+    (i32.add
      (local.get $x32)
      (i32.const 30)
     )
@@ -4205,15 +4205,15 @@
  )
  (func $rhs-is-neg-one (param $x i32) (param $y i64) (param $fx f32) (param $fy f64)
   (drop
-   (i32.sub
+   (i32.add
     (local.get $x)
-    (i32.const -1)
+    (i32.const 1)
    )
   )
   (drop
-   (i64.sub
+   (i64.add
     (local.get $y)
-    (i64.const -1)
+    (i64.const 1)
    )
   )
   (drop