amd64: fixes memory.fill bug (#1055)

Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io>
Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>

internal/engine/compiler/impl_amd64.go

@@ -3799,6 +3799,8 @@ func (c *amd64Compiler) compileFillLoopImpl(destinationOffset, value, fillSize *
 	emptyEightGroupsJump := c.assembler.CompileJump(amd64.JEQ)
 
 	if replicateByte {
+		// Truncate value.register to a single byte
+		c.assembler.CompileConstToRegister(amd64.ANDQ, 0xff, value.register)
 		// Replicate single byte onto full 8-byte register.
 		c.assembler.CompileConstToRegister(amd64.MOVQ, 0x0101010101010101, tmp)
 		c.assembler.CompileRegisterToRegister(amd64.IMULQ, tmp, value.register)

internal/integration_test/fuzzcases/fuzzcases_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/tetratelabs/wazero"
+	"github.com/tetratelabs/wazero/api"
 	"github.com/tetratelabs/wazero/internal/platform"
 	"github.com/tetratelabs/wazero/internal/testing/require"
 	"github.com/tetratelabs/wazero/internal/wasm"
@@ -383,3 +384,22 @@ func Test888(t *testing.T) {
 		require.NoError(t, err)
 	})
 }
+
+func Test1054(t *testing.T) {
+	if !platform.CompilerSupported() {
+		return
+	}
+
+	modules := make([]api.Module, 0, 2)
+	run(t, func(t *testing.T, r wazero.Runtime) {
+		mod, err := r.InstantiateModuleFromBinary(ctx, getWasmBinary(t, 1054))
+		require.NoError(t, err)
+		modules = append(modules, mod)
+	})
+
+	// Checks if the memory state is the same between engines.
+	require.Equal(t,
+		modules[0].Memory().(*wasm.MemoryInstance).Buffer,
+		modules[1].Memory().(*wasm.MemoryInstance).Buffer,
+	)
+}

internal/integration_test/fuzzcases/testdata/1054.wat

@@ -0,0 +1,11 @@
+(module
+  (type (;0;) (func))
+  (func (;0;) (type 0)
+    i32.const 1000
+    i32.const 1000
+    i32.const 1000
+    memory.fill
+  )
+  (memory (;0;) 1 2)
+  (start 0)
+)