From 2fceb336fd4868062a3e7dbac169a571ffd2a0b3 Mon Sep 17 00:00:00 2001
From: andreatp <andrea.peruffo1982@gmail.com>
Date: Tue, 22 Sep 2026 18:01:17 +0100
Subject: [PATCH] Fix v128 local.set and local.tee word order in the
 interpreter

---
 .../run/endive/runtime/InterpreterMachine.java  |  10 +++++-----
 .../java/run/endive/simd/BasicSimdTest.java     |  15 +++++++++++++++
 .../resources/compiled/simd-locals.wat.wasm     | Bin 0 -> 217 bytes
 .../src/main/resources/wat/simd-locals.wat      |  16 ++++++++++++++++
 4 files changed, 36 insertions(+), 5 deletions(-)
 create mode 100644 wasm-corpus/src/main/resources/compiled/simd-locals.wat.wasm
 create mode 100644 wasm-corpus/src/main/resources/wat/simd-locals.wat

diff --git a/runtime/src/main/java/run/endive/runtime/InterpreterMachine.java b/runtime/src/main/java/run/endive/runtime/InterpreterMachine.java
index e686c7fef..ebefdb4d1 100644
--- a/runtime/src/main/java/run/endive/runtime/InterpreterMachine.java
+++ b/runtime/src/main/java/run/endive/runtime/InterpreterMachine.java
@@ -2457,8 +2457,8 @@ private static void LOCAL_SET(MStack stack, Operands operands, StackFrame curren
         if (localType.isObjectRef()) {
             currentStackFrame.setLocalRef(i, stack.popRef());
         } else if (localType.equals(ValType.V128)) {
-            currentStackFrame.setLocal(i, stack.pop());
             currentStackFrame.setLocal(i + 1, stack.pop());
+            currentStackFrame.setLocal(i, stack.pop());
         } else {
             currentStackFrame.setLocal(i, stack.pop());
         }
@@ -2472,10 +2472,10 @@ private static void LOCAL_TEE(MStack stack, Operands operands, StackFrame curren
         if (localType.isObjectRef()) {
             currentStackFrame.setLocalRef(i, stack.peekRef());
         } else if (localType.equals(ValType.V128)) {
-            var tmp = stack.pop();
-            currentStackFrame.setLocal(i, tmp);
-            currentStackFrame.setLocal(i + 1, stack.peek());
-            stack.push(tmp);
+            var high = stack.pop();
+            currentStackFrame.setLocal(i + 1, high);
+            currentStackFrame.setLocal(i, stack.peek());
+            stack.push(high);
         } else {
             currentStackFrame.setLocal(i, stack.peek());
         }
diff --git a/simd/src/test/java/run/endive/simd/BasicSimdTest.java b/simd/src/test/java/run/endive/simd/BasicSimdTest.java
index f4168bddb..8a069943f 100644
--- a/simd/src/test/java/run/endive/simd/BasicSimdTest.java
+++ b/simd/src/test/java/run/endive/simd/BasicSimdTest.java
@@ -23,4 +23,19 @@ public void shouldRunBasicExample() {
         var result = main.apply()[0];
         assertEquals(6L, result);
     }
+
+    @Test
+    public void shouldRoundTripV128Locals() {
+        var instance =
+                Instance.builder(
+                                Parser.parse(
+                                        CorpusResources.getResource(
+                                                "compiled/simd-locals.wat.wasm")))
+                        .withMachineFactory(SimdInterpreterMachine::new)
+                        .build();
+        assertEquals(10L, instance.export("local_roundtrip").apply()[0]);
+        assertEquals(7L, instance.export("local_roundtrip_lane0").apply()[0]);
+        assertEquals(10L, instance.export("local_tee").apply()[0]);
+        assertEquals(7L, instance.export("local_tee_get").apply()[0]);
+    }
 }
diff --git a/wasm-corpus/src/main/resources/compiled/simd-locals.wat.wasm b/wasm-corpus/src/main/resources/compiled/simd-locals.wat.wasm
new file mode 100644
index 0000000000000000000000000000000000000000..db52c63277cd324f8055b97446adb755a8fafd2f
GIT binary patch
literal 217
zcmZQbEY4+QU|?WmWlUgTtY>Cr0dg4F-C6i^@{<#D;*0W2^HNHRG7A_OMA1aza}x7X
z4Hy_XA>t*esSHfKaCUrpY6$}~R|ShKBV+Yn9(JIq96-zo#9TnE$e_URSDKj{pDY8n
TG*-PzV4ZR}<fK3bGjIa{G<hep

literal 0
HcmV?d00001

diff --git a/wasm-corpus/src/main/resources/wat/simd-locals.wat b/wasm-corpus/src/main/resources/wat/simd-locals.wat
new file mode 100644
index 000000000..e98574a66
--- /dev/null
+++ b/wasm-corpus/src/main/resources/wat/simd-locals.wat
@@ -0,0 +1,16 @@
+(module
+  (func (export "local_roundtrip") (result i32) (local v128)
+    (local.set 0 (v128.const i32x4 7 8 9 10))
+    (i32x4.extract_lane 3 (local.get 0)))
+
+  (func (export "local_roundtrip_lane0") (result i32) (local v128)
+    (local.set 0 (v128.const i32x4 7 8 9 10))
+    (i32x4.extract_lane 0 (local.get 0)))
+
+  (func (export "local_tee") (result i32) (local v128)
+    (i32x4.extract_lane 3 (local.tee 0 (v128.const i32x4 7 8 9 10))))
+
+  (func (export "local_tee_get") (result i32) (local v128)
+    (drop (local.tee 0 (v128.const i32x4 7 8 9 10)))
+    (i32x4.extract_lane 0 (local.get 0)))
+)