Optimize signed division when RHS is signed minimum (#3221)

1 files changed, 17 insertions, 0 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 2736c8984..232faab7a 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -1454,6 +1454,23 @@ private:
       right->value = Literal::makeZero(type);
       return right;
     }
+    // i32(x) / i32.min_s   ==>   x == i32.min_s
+    if (matches(
+          curr,
+          binary(DivSInt32, any(), i32(std::numeric_limits<int32_t>::min())))) {
+      curr->op = EqInt32;
+      return curr;
+    }
+    // i64(x) / i64.min_s   ==>   i64(x == i64.min_s)
+    // only for zero shrink level
+    if (getPassOptions().shrinkLevel == 0 &&
+        matches(
+          curr,
+          binary(DivSInt64, any(), i64(std::numeric_limits<int64_t>::min())))) {
+      curr->op = EqInt64;
+      curr->type = Type::i32;
+      return Builder(*getModule()).makeUnary(ExtendUInt32, curr);
+    }
     // (unsigned)x > -1   ==>   0
     if (matches(curr, binary(Abstract::GtU, pure(&left), ival(-1)))) {
       right->value = Literal::makeZero(Type::i32);