Simplify signed remainders compared with zero (#3153)

Specifically when the divisor is a power of two.

`eqz((signed)x % C_pot)` -> `eqz(x & (C_pot - 1))`
`(signed)x % C_pot != 0` -> `x & (C_pot - 1) != 0`

2 files changed, 143 insertions, 1 deletions

diff --git a/test/passes/optimize-instructions_all-features.txt b/test/passes/optimize-instructions_all-features.txt
index e3ad30a0b..860783f36 100644
--- a/test/passes/optimize-instructions_all-features.txt
+++ b/test/passes/optimize-instructions_all-features.txt
@@ -2,8 +2,8 @@
  (type $i32_i32_=>_none (func (param i32 i32)))
  (type $i32_=>_i32 (func (param i32) (result i32)))
  (type $none_=>_i32 (func (result i32)))
- (type $none_=>_none (func))
  (type $i32_i64_=>_none (func (param i32 i64)))
+ (type $none_=>_none (func))
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
  (type $i32_=>_none (func (param i32)))
  (type $none_=>_i64 (func (result i64)))
@@ -2744,6 +2744,81 @@
    (i64.const 0)
   )
  )
+ (func $srem-by-pot-eq-ne-zero (param $x i32) (param $y i64)
+  (drop
+   (i32.eqz
+    (i32.and
+     (local.get $x)
+     (i32.const 3)
+    )
+   )
+  )
+  (drop
+   (i64.eqz
+    (i64.and
+     (local.get $y)
+     (i64.const 3)
+    )
+   )
+  )
+  (drop
+   (i32.eqz
+    (i32.and
+     (local.get $x)
+     (i32.const 3)
+    )
+   )
+  )
+  (drop
+   (i64.eqz
+    (i64.and
+     (local.get $y)
+     (i64.const 1)
+    )
+   )
+  )
+  (drop
+   (i32.ne
+    (i32.and
+     (local.get $x)
+     (i32.const 1)
+    )
+    (i32.const 0)
+   )
+  )
+  (drop
+   (i32.wrap_i64
+    (i64.and
+     (local.get $y)
+     (i64.const 1)
+    )
+   )
+  )
+  (drop
+   (i32.eqz
+    (i32.rem_s
+     (local.get $x)
+     (i32.const 3)
+    )
+   )
+  )
+  (drop
+   (i32.eqz
+    (i32.rem_s
+     (local.get $x)
+     (i32.const -4)
+    )
+   )
+  )
+  (drop
+   (i64.eqz
+    (i64.rem_s
+     (local.get $y)
+     (i64.const 3)
+    )
+   )
+  )
+ )
  (func $orZero (param $0 i32) (result i32)
   (local.get $0)
  )
diff --git a/test/passes/optimize-instructions_all-features.wast b/test/passes/optimize-instructions_all-features.wast
index 8c2cefb53..1afa3e5b5 100644
--- a/test/passes/optimize-instructions_all-features.wast
+++ b/test/passes/optimize-instructions_all-features.wast
@@ -3104,6 +3104,73 @@
       (i64.const 1)
     ))
   )
+  (func $srem-by-pot-eq-ne-zero (param $x i32) (param $y i64)
+    ;; eqz((signed)x % 4)
+    (drop (i32.eqz
+      (i32.rem_s
+        (local.get $x)
+        (i32.const 4)
+      )
+    ))
+    (drop (i64.eqz
+      (i64.rem_s
+        (local.get $y)
+        (i64.const 4)
+      )
+    ))
+    ;; (signed)x % 4 == 0
+    (drop (i32.eq
+      (i32.rem_s
+        (local.get $x)
+        (i32.const 4)
+      )
+      (i32.const 0)
+    ))
+    (drop (i64.eq
+      (i64.rem_s
+        (local.get $y)
+        (i64.const 2)
+      )
+      (i64.const 0)
+    ))
+    ;; ;; (signed)x % 2 != 0
+    (drop (i32.ne
+      (i32.rem_s
+        (local.get $x)
+        (i32.const 2)
+      )
+      (i32.const 0)
+    ))
+    (drop (i64.ne
+      (i64.rem_s
+        (local.get $y)
+        (i64.const 2)
+      )
+      (i64.const 0)
+    ))
+    ;; ;;
+    (drop (i32.eq
+      (i32.rem_s
+        (local.get $x)
+        (i32.const 3) ;; skip
+      )
+      (i32.const 0)
+    ))
+    (drop (i32.eq
+      (i32.rem_s
+        (local.get $x)
+        (i32.const -4) ;; skip
+      )
+      (i32.const 0)
+    ))
+    (drop (i64.eq
+      (i64.rem_s
+        (local.get $y)
+        (i64.const 3) ;; skip
+      )
+      (i64.const 0)
+    ))
+  )
   (func $orZero (param $0 i32) (result i32)
     (i32.or
       (local.get $0)