[OptimizeInstructions] Simplify rounding or conversions after int to float casts (#4720)

i32 -> f64 -> i32 rountripping optimizations:
```rust
i32(f64(i32(x)))   ->   x // i32.trunc(_sat)_f64_s(f64.convert_i32_s(x)) -> x
u32(f64(u32(x)))   ->   x // i32.trunc(_sat)_f64_u(f64.convert_i32_u(x)) -> x

// note assymetric signed / unsigned or unsigned / signed cases can't be simplified in similar way
```
and rounding after integer to float casts:
```rust
ceil(float(int(x)))     ->  float(int(x))
floor(float(int(x)))    ->  float(int(x))
trunc(float(int(x)))    ->  float(int(x))
nearest(float(int(x)))  ->  float(int(x))
```
where `float = f32 | f64`, `int = i32 | i64 | u32 | u64`

3 files changed, 439 insertions, 0 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 4fe26e8ee..394a7c998 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -1039,6 +1039,10 @@ struct OptimizeInstructions
     if (auto* ret = deduplicateUnary(curr)) {
       return replaceCurrent(ret);
     }
+
+    if (auto* ret = simplifyRoundingsAndConversions(curr)) {
+      return replaceCurrent(ret);
+    }
   }
 
   void visitSelect(Select* curr) {
@@ -3619,6 +3623,69 @@ private:
     return nullptr;
   }
 
+  Expression* simplifyRoundingsAndConversions(Unary* curr) {
+    using namespace Abstract;
+    using namespace Match;
+
+    switch (curr->op) {
+      case TruncSFloat64ToInt32:
+      case TruncSatSFloat64ToInt32: {
+        // i32 -> f64 -> i32 rountripping optimization:
+        //   i32.trunc(_sat)_f64_s(f64.convert_i32_s(x))  ==>  x
+        Expression* x;
+        if (matches(curr->value, unary(ConvertSInt32ToFloat64, any(&x)))) {
+          return x;
+        }
+        break;
+      }
+      case TruncUFloat64ToInt32:
+      case TruncSatUFloat64ToInt32: {
+        // u32 -> f64 -> u32 rountripping optimization:
+        //   i32.trunc(_sat)_f64_u(f64.convert_i32_u(x))  ==>  x
+        Expression* x;
+        if (matches(curr->value, unary(ConvertUInt32ToFloat64, any(&x)))) {
+          return x;
+        }
+        break;
+      }
+      case CeilFloat32:
+      case CeilFloat64:
+      case FloorFloat32:
+      case FloorFloat64:
+      case TruncFloat32:
+      case TruncFloat64:
+      case NearestFloat32:
+      case NearestFloat64: {
+        // Rounding after integer to float conversion may be skipped
+        //   ceil(float(int(x)))     ==>  float(int(x))
+        //   floor(float(int(x)))    ==>  float(int(x))
+        //   trunc(float(int(x)))    ==>  float(int(x))
+        //   nearest(float(int(x)))  ==>  float(int(x))
+        Unary* inner;
+        if (matches(curr->value, unary(&inner, any()))) {
+          switch (inner->op) {
+            case ConvertSInt32ToFloat32:
+            case ConvertSInt32ToFloat64:
+            case ConvertUInt32ToFloat32:
+            case ConvertUInt32ToFloat64:
+            case ConvertSInt64ToFloat32:
+            case ConvertSInt64ToFloat64:
+            case ConvertUInt64ToFloat32:
+            case ConvertUInt64ToFloat64: {
+              return inner;
+            }
+            default: {
+            }
+          }
+        }
+        break;
+      }
+      default: {
+      }
+    }
+    return nullptr;
+  }
+
   Expression* deduplicateUnary(Unary* unaryOuter) {
     if (auto* unaryInner = unaryOuter->value->dynCast<Unary>()) {
       if (unaryInner->op == unaryOuter->op) {
diff --git a/test/lit/passes/optimize-instructions-nontrapping-float-to-int.wast b/test/lit/passes/optimize-instructions-nontrapping-float-to-int.wast
new file mode 100644
index 000000000..d3e759e1c
--- /dev/null
+++ b/test/lit/passes/optimize-instructions-nontrapping-float-to-int.wast
@@ -0,0 +1,77 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+;; RUN: wasm-opt %s --optimize-instructions --enable-nontrapping-float-to-int -S -o - | filecheck %s
+
+(module
+  (memory 0)
+
+  ;; CHECK:      (func $simplify_int_float_sat_conversion_roundtrips (param $x i32) (param $y i64)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (local.get $x)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (local.get $x)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_sat_f64_s
+  ;; CHECK-NEXT:    (f64.convert_i32_u
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_sat_f64_u
+  ;; CHECK-NEXT:    (f64.convert_i32_s
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_sat_f32_u
+  ;; CHECK-NEXT:    (f32.convert_i32_u
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_sat_f64_u
+  ;; CHECK-NEXT:    (f64.convert_i64_u
+  ;; CHECK-NEXT:     (local.get $y)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i64.trunc_sat_f64_s
+  ;; CHECK-NEXT:    (f64.convert_i64_s
+  ;; CHECK-NEXT:     (local.get $y)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i64.trunc_sat_f32_u
+  ;; CHECK-NEXT:    (f32.convert_i32_s
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i64.trunc_sat_f32_s
+  ;; CHECK-NEXT:    (f32.convert_i64_s
+  ;; CHECK-NEXT:     (local.get $y)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $simplify_int_float_sat_conversion_roundtrips (param $x i32) (param $y i64)
+    (drop (i32.trunc_sat_f64_u (f64.convert_i32_u (local.get $x))))
+    (drop (i32.trunc_sat_f64_s (f64.convert_i32_s (local.get $x))))
+
+    ;; skips
+    (drop (i32.trunc_sat_f64_s (f64.convert_i32_u (local.get $x))))
+    (drop (i32.trunc_sat_f64_u (f64.convert_i32_s (local.get $x))))
+    (drop (i32.trunc_sat_f32_u (f32.convert_i32_u (local.get $x))))
+    (drop (i32.trunc_sat_f64_u (f64.convert_i64_u (local.get $y))))
+    (drop (i64.trunc_sat_f64_s (f64.convert_i64_s (local.get $y))))
+    (drop (i64.trunc_sat_f32_u (f32.convert_i32_s (local.get $x))))
+    (drop (i64.trunc_sat_f32_s (f32.convert_i64_s (local.get $y))))
+  )
+)
diff --git a/test/lit/passes/optimize-instructions.wast b/test/lit/passes/optimize-instructions.wast
index 1bf3f751c..e90eba2a8 100644
--- a/test/lit/passes/optimize-instructions.wast
+++ b/test/lit/passes/optimize-instructions.wast
@@ -14092,6 +14092,301 @@
     (drop (f64.reinterpret_i64 (i64.reinterpret_f64 (local.get $w))))
   )
 
+  ;; CHECK:      (func $simplify_int_float_conversion_roundtrips (param $x i32) (param $y i64)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (local.get $x)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (local.get $x)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_f64_u
+  ;; CHECK-NEXT:    (f64.convert_i32_s
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_f64_s
+  ;; CHECK-NEXT:    (f64.convert_i32_u
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_f32_u
+  ;; CHECK-NEXT:    (f32.convert_i32_u
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.trunc_f64_u
+  ;; CHECK-NEXT:    (f64.convert_i64_u
+  ;; CHECK-NEXT:     (local.get $y)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i64.trunc_f64_s
+  ;; CHECK-NEXT:    (f64.convert_i64_s
+  ;; CHECK-NEXT:     (local.get $y)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i64.trunc_f32_u
+  ;; CHECK-NEXT:    (f32.convert_i32_s
+  ;; CHECK-NEXT:     (local.get $x)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i64.trunc_f32_s
+  ;; CHECK-NEXT:    (f32.convert_i64_s
+  ;; CHECK-NEXT:     (local.get $y)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $simplify_int_float_conversion_roundtrips (param $x i32) (param $y i64)
+    (drop (i32.trunc_f64_u (f64.convert_i32_u (local.get $x))))
+    (drop (i32.trunc_f64_s (f64.convert_i32_s (local.get $x))))
+
+    ;; skips
+    (drop (i32.trunc_f64_u (f64.convert_i32_s (local.get $x))))
+    (drop (i32.trunc_f64_s (f64.convert_i32_u (local.get $x))))
+    (drop (i32.trunc_f32_u (f32.convert_i32_u (local.get $x))))
+    (drop (i32.trunc_f64_u (f64.convert_i64_u (local.get $y))))
+    (drop (i64.trunc_f64_s (f64.convert_i64_s (local.get $y))))
+    (drop (i64.trunc_f32_u (f32.convert_i32_s (local.get $x))))
+    (drop (i64.trunc_f32_s (f32.convert_i64_s (local.get $y))))
+  )
+
+  ;; CHECK:      (func $simplify_rounding_after_conversions_i32_to_f64 (param $x i32)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $simplify_rounding_after_conversions_i32_to_f64 (param $x i32)
+    (drop (f64.ceil (f64.convert_i32_u (local.get $x))))
+    (drop (f64.ceil (f64.convert_i32_s (local.get $x))))
+
+    (drop (f64.floor (f64.convert_i32_u (local.get $x))))
+    (drop (f64.floor (f64.convert_i32_s (local.get $x))))
+
+    (drop (f64.trunc (f64.convert_i32_u (local.get $x))))
+    (drop (f64.trunc (f64.convert_i32_s (local.get $x))))
+
+    (drop (f64.nearest (f64.convert_i32_u (local.get $x))))
+    (drop (f64.nearest (f64.convert_i32_s (local.get $x))))
+  )
+
+  ;; CHECK:      (func $simplify_rounding_after_conversions_i32_to_f32 (param $x i32)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i32_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $simplify_rounding_after_conversions_i32_to_f32 (param $x i32)
+    (drop (f32.ceil (f32.convert_i32_u (local.get $x))))
+    (drop (f32.ceil (f32.convert_i32_s (local.get $x))))
+
+    (drop (f32.floor (f32.convert_i32_u (local.get $x))))
+    (drop (f32.floor (f32.convert_i32_s (local.get $x))))
+
+    (drop (f32.trunc (f32.convert_i32_u (local.get $x))))
+    (drop (f32.trunc (f32.convert_i32_s (local.get $x))))
+
+    (drop (f32.nearest (f32.convert_i32_u (local.get $x))))
+    (drop (f32.nearest (f32.convert_i32_s (local.get $x))))
+  )
+
+  ;; CHECK:      (func $simplify_rounding_after_conversions_i64_to_f64 (param $x i64)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f64.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $simplify_rounding_after_conversions_i64_to_f64 (param $x i64)
+    (drop (f64.ceil (f64.convert_i64_u (local.get $x))))
+    (drop (f64.ceil (f64.convert_i64_s (local.get $x))))
+
+    (drop (f64.floor (f64.convert_i64_u (local.get $x))))
+    (drop (f64.floor (f64.convert_i64_s (local.get $x))))
+
+    (drop (f64.trunc (f64.convert_i64_u (local.get $x))))
+    (drop (f64.trunc (f64.convert_i64_s (local.get $x))))
+
+    (drop (f64.nearest (f64.convert_i64_u (local.get $x))))
+    (drop (f64.nearest (f64.convert_i64_s (local.get $x))))
+  )
+
+  ;; CHECK:      (func $simplify_rounding_after_conversions_i64_to_f32 (param $x i64)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_u
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (f32.convert_i64_s
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $simplify_rounding_after_conversions_i64_to_f32 (param $x i64)
+    (drop (f32.ceil (f32.convert_i64_u (local.get $x))))
+    (drop (f32.ceil (f32.convert_i64_s (local.get $x))))
+
+    (drop (f32.floor (f32.convert_i64_u (local.get $x))))
+    (drop (f32.floor (f32.convert_i64_s (local.get $x))))
+
+    (drop (f32.trunc (f32.convert_i64_u (local.get $x))))
+    (drop (f32.trunc (f32.convert_i64_s (local.get $x))))
+
+    (drop (f32.nearest (f32.convert_i64_u (local.get $x))))
+    (drop (f32.nearest (f32.convert_i64_s (local.get $x))))
+  )
+
   ;; u64(i32.load(_8|_16)(_u|_s)(x))  =>  i64.load(_8|_16|_32)(_u|_s)(x)
   ;; except:
   ;;   i64.extend_i32_u(i32.load8_s(x)) and