SimplifyGlobals: If all writes write the initial value, they are unneeded (#4356)

1 files changed, 143 insertions, 0 deletions

diff --git a/test/lit/passes/simplify-globals-non-init.wast b/test/lit/passes/simplify-globals-non-init.wast
new file mode 100644
index 000000000..9e3230319
--- /dev/null
+++ b/test/lit/passes/simplify-globals-non-init.wast
@@ -0,0 +1,143 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; NOTE: This test was ported using port_test.py and could be cleaned up.
+
+;; RUN: foreach %s %t wasm-opt --simplify-globals --enable-mutable-globals -S -o - | filecheck %s
+
+;; A global that is written its initial value in all subsequent writes can
+;; remove those writes.
+(module
+  ;; CHECK:      (type $none_=>_none (func))
+
+  ;; CHECK:      (global $global-0 i32 (i32.const 0))
+  (global $global-0 (mut i32) (i32.const 0))
+  ;; CHECK:      (global $global-1 i32 (i32.const 1))
+  (global $global-1 (mut i32) (i32.const 1))
+
+  ;; CHECK:      (func $sets
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $sets
+    ;; All these writes can be turned into drops.
+
+    (global.set $global-0 (i32.const 0))
+    (global.set $global-0 (i32.const 0))
+
+    (global.set $global-1 (i32.const 1))
+    (global.set $global-1 (i32.const 1))
+  )
+
+  ;; CHECK:      (func $gets
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $gets
+    ;; Add gets to avoid other opts from removing the sets.
+    (drop (global.get $global-0))
+    (drop (global.get $global-1))
+  )
+)
+
+;; As above, but now we write other values.
+(module
+  ;; CHECK:      (type $i32_=>_none (func (param i32)))
+
+  ;; CHECK:      (type $none_=>_none (func))
+
+  ;; CHECK:      (global $global-0 (mut i32) (i32.const 0))
+  (global $global-0 (mut i32) (i32.const 0))
+  ;; CHECK:      (global $global-1 (mut i32) (i32.const 1))
+  (global $global-1 (mut i32) (i32.const 1))
+
+  ;; CHECK:      (func $sets (param $unknown i32)
+  ;; CHECK-NEXT:  (global.set $global-0
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (global.set $global-0
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (global.set $global-1
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (global.set $global-1
+  ;; CHECK-NEXT:   (local.get $unknown)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $sets (param $unknown i32)
+    (global.set $global-0 (i32.const 0))
+    (global.set $global-0 (i32.const 1)) ;; a non-init value
+
+    (global.set $global-1 (i32.const 1))
+    (global.set $global-1 (local.get $unknown)) ;; a totally unknown value
+  )
+
+  ;; CHECK:      (func $gets
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (global.get $global-0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (global.get $global-1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $gets
+    (drop (global.get $global-0))
+    (drop (global.get $global-1))
+  )
+)
+
+;; Globals without constant initial values.
+(module
+  ;; An imported global.
+  ;; CHECK:      (type $i32_=>_none (func (param i32)))
+
+  ;; CHECK:      (type $none_=>_none (func))
+
+  ;; CHECK:      (import "env" "import_global" (global $global-0 (mut i32)))
+  (import "env" "import_global" (global $global-0 (mut i32)))
+
+  ;; A global that initializes with another global.
+  ;; CHECK:      (global $global-1 (mut i32) (global.get $global-0))
+  (global $global-1 (mut i32) (global.get $global-0))
+
+  ;; CHECK:      (func $sets (param $unknown i32)
+  ;; CHECK-NEXT:  (global.set $global-0
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (global.set $global-1
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $sets (param $unknown i32)
+    (global.set $global-0 (i32.const 0))
+
+    (global.set $global-1 (i32.const 1))
+  )
+
+  ;; CHECK:      (func $gets
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (global.get $global-0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (global.get $global-1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $gets
+    ;; Add gets to avoid other opts from removing the sets.
+    (drop (global.get $global-0))
+    (drop (global.get $global-1))
+  )
+)