fix popcnt for aarch64

lib/compiler-singlepass/src/machine_arm64.rs

@@ -3052,11 +3052,11 @@ impl Machine for MachineARM64 {
         self.assembler.emit_cbz_label(Size::S32, src, label_exit)?; // src==0, exit
         self.assembler.emit_label(label_loop)?; // loop:
         self.assembler
-            .emit_add(Size::S32, dest, Location::Imm8(1), dest)?; // inc dest
+            .emit_add(Size::S32, dest, Location::Imm8(1), dest)?; // dest += 1
         self.assembler.emit_clz(Size::S32, src, tmp)?; // clz src => tmp
-        self.assembler
-            .emit_add(Size::S32, tmp, Location::Imm8(1), tmp)?; // inc tmp
         self.assembler.emit_lsl(Size::S32, src, tmp, src)?; // src << tmp => src
+        self.assembler
+            .emit_lsl(Size::S32, src, Location::Imm8(1), src)?; // src << 1 => src
         self.assembler.emit_cbnz_label(Size::S32, src, label_loop)?; // if src!=0 goto loop
         self.assembler.emit_label(label_exit)?;
         if ret != dest {
@@ -4086,16 +4086,16 @@ impl Machine for MachineARM64 {
         let label_loop = self.assembler.get_label();
         let label_exit = self.assembler.get_label();
         self.assembler
-            .emit_mov(Size::S32, Location::GPR(GPR::XzrSp), dest)?;
-        self.assembler.emit_cbz_label(Size::S64, src, label_exit)?;
+            .emit_mov(Size::S32, Location::GPR(GPR::XzrSp), dest)?; // dest <= 0
+        self.assembler.emit_cbz_label(Size::S64, src, label_exit)?; // src == 0, then goto label_exit
         self.assembler.emit_label(label_loop)?;
         self.assembler
-            .emit_add(Size::S32, dest, Location::Imm8(1), dest)?;
-        self.assembler.emit_clz(Size::S64, src, tmp)?;
+            .emit_add(Size::S32, dest, Location::Imm8(1), dest)?; // dest += 1
+        self.assembler.emit_clz(Size::S64, src, tmp)?; // clz src => tmp
+        self.assembler.emit_lsl(Size::S64, src, tmp, src)?; // src << tmp => src
         self.assembler
-            .emit_add(Size::S32, tmp, Location::Imm8(1), tmp)?;
-        self.assembler.emit_lsl(Size::S64, src, tmp, src)?;
-        self.assembler.emit_cbnz_label(Size::S64, src, label_loop)?;
+            .emit_lsl(Size::S64, src, Location::Imm8(1), src)?; // src << 1 => src
+        self.assembler.emit_cbnz_label(Size::S64, src, label_loop)?; // src != 0, then goto label_loop
         self.assembler.emit_label(label_exit)?;
         if ret != dest {
             self.move_location(Size::S64, dest, ret)?;

tests/compilers/issues.rs

@@ -263,3 +263,57 @@ fn regression_gpr_exhaustion_for_calls(mut config: crate::Config) -> Result<()>
     let instance = Instance::new(&mut store, &module, &imports)?;
     Ok(())
 }
+
+#[compiler_test(issues)]
+fn test_popcnt(mut config: crate::Config) -> Result<()> {
+    let mut store = config.store();
+    let mut env = FunctionEnv::new(&mut store, ());
+    let imports: Imports = imports! {};
+
+    let wat = r#"
+    (module
+        (func $popcnt_i32 (export "popcnt_i32") (param i32) (result i32)
+            local.get 0
+            i32.popcnt
+        )
+        (func $popcnt_i64 (export "popcnt_i64") (param i64) (result i64)
+            local.get 0
+            i64.popcnt
+        )
+    )"#;
+
+    let module = Module::new(&store, wat)?;
+    let instance = Instance::new(&mut store, &module, &imports)?;
+
+    let popcnt_i32 = instance.exports.get_function("popcnt_i32").unwrap();
+    let popcnt_i64 = instance.exports.get_function("popcnt_i64").unwrap();
+
+    let get_next_number_i32 = |mut num: i32| {
+        num ^= num << 13;
+        num ^= num >> 17;
+        num ^= num << 5;
+        num
+    };
+    let get_next_number_i64 = |mut num: i64| {
+        num ^= num << 34;
+        num ^= num >> 40;
+        num ^= num << 7;
+        num
+    };
+
+    let mut num = 1;
+    for _ in 1..10000 {
+        let result = popcnt_i32.call(&mut store, &[Value::I32(num)]).unwrap();
+        assert_eq!(&Value::I32(num.count_ones() as i32), result.get(0).unwrap());
+        num = get_next_number_i32(num);
+    }
+
+    let mut num = 1;
+    for _ in 1..10000 {
+        let result = popcnt_i64.call(&mut store, &[Value::I64(num)]).unwrap();
+        assert_eq!(&Value::I64(num.count_ones() as i64), result.get(0).unwrap());
+        num = get_next_number_i64(num);
+    }
+
+    Ok(())
+}