diff --git a/libs/vkd3d-shader/hlsl.h b/libs/vkd3d-shader/hlsl.h
index 2e8ba4af..0543e144 100644
--- a/libs/vkd3d-shader/hlsl.h
+++ b/libs/vkd3d-shader/hlsl.h
@@ -794,8 +794,7 @@ unsigned int hlsl_swizzle_from_writemask(unsigned int writemask);
 
 bool hlsl_offset_from_deref(struct hlsl_ctx *ctx, const struct hlsl_deref *deref, unsigned int *offset);
 unsigned int hlsl_offset_from_deref_safe(struct hlsl_ctx *ctx, const struct hlsl_deref *deref);
-struct hlsl_reg hlsl_reg_from_deref(struct hlsl_ctx *ctx, const struct hlsl_deref *deref,
-        const struct hlsl_type *type);
+struct hlsl_reg hlsl_reg_from_deref(struct hlsl_ctx *ctx, const struct hlsl_deref *deref);
 
 bool hlsl_fold_constants(struct hlsl_ctx *ctx, struct hlsl_ir_node *instr, void *context);
 
diff --git a/libs/vkd3d-shader/hlsl_codegen.c b/libs/vkd3d-shader/hlsl_codegen.c
index ca3acba0..98be3aeb 100644
--- a/libs/vkd3d-shader/hlsl_codegen.c
+++ b/libs/vkd3d-shader/hlsl_codegen.c
@@ -1542,11 +1542,6 @@ static void allocate_objects(struct hlsl_ctx *ctx, enum hlsl_base_type type)
     }
 }
 
-static bool type_is_single_reg(const struct hlsl_type *type)
-{
-    return type->type == HLSL_CLASS_SCALAR || type->type == HLSL_CLASS_VECTOR;
-}
-
 bool hlsl_offset_from_deref(struct hlsl_ctx *ctx, const struct hlsl_deref *deref, unsigned int *offset)
 {
     struct hlsl_ir_node *offset_node = deref->offset.node;
@@ -1589,8 +1584,7 @@ unsigned int hlsl_offset_from_deref_safe(struct hlsl_ctx *ctx, const struct hlsl
     return 0;
 }
 
-struct hlsl_reg hlsl_reg_from_deref(struct hlsl_ctx *ctx, const struct hlsl_deref *deref,
-        const struct hlsl_type *type)
+struct hlsl_reg hlsl_reg_from_deref(struct hlsl_ctx *ctx, const struct hlsl_deref *deref)
 {
     const struct hlsl_ir_var *var = deref->var;
     struct hlsl_reg ret = var->reg;
@@ -1598,16 +1592,10 @@ struct hlsl_reg hlsl_reg_from_deref(struct hlsl_ctx *ctx, const struct hlsl_dere
 
     ret.id += offset / 4;
 
-    if (type_is_single_reg(var->data_type))
-    {
-        assert(!offset);
-        ret.writemask = var->reg.writemask;
-    }
-    else
-    {
-        assert(type_is_single_reg(type));
-        ret.writemask = ((1 << type->dimx) - 1) << (offset % 4);
-    }
+    ret.writemask = 0xf & (0xf << (offset % 4));
+    if (var->reg.writemask)
+        ret.writemask = hlsl_combine_writemasks(var->reg.writemask, ret.writemask);
+
     return ret;
 }
 
diff --git a/libs/vkd3d-shader/hlsl_sm1.c b/libs/vkd3d-shader/hlsl_sm1.c
index 90ec6058..f661dbc2 100644
--- a/libs/vkd3d-shader/hlsl_sm1.c
+++ b/libs/vkd3d-shader/hlsl_sm1.c
@@ -663,7 +663,7 @@ static void write_sm1_expr(struct hlsl_ctx *ctx, struct vkd3d_bytecode_buffer *b
 static void write_sm1_load(struct hlsl_ctx *ctx, struct vkd3d_bytecode_buffer *buffer, const struct hlsl_ir_node *instr)
 {
     const struct hlsl_ir_load *load = hlsl_ir_load(instr);
-    const struct hlsl_reg reg = hlsl_reg_from_deref(ctx, &load->src, instr->data_type);
+    const struct hlsl_reg reg = hlsl_reg_from_deref(ctx, &load->src);
     struct sm1_instruction sm1_instr =
     {
         .opcode = D3DSIO_MOV,
@@ -707,7 +707,7 @@ static void write_sm1_store(struct hlsl_ctx *ctx, struct vkd3d_bytecode_buffer *
 {
     const struct hlsl_ir_store *store = hlsl_ir_store(instr);
     const struct hlsl_ir_node *rhs = store->rhs.node;
-    const struct hlsl_reg reg = hlsl_reg_from_deref(ctx, &store->lhs, rhs->data_type);
+    const struct hlsl_reg reg = hlsl_reg_from_deref(ctx, &store->lhs);
     struct sm1_instruction sm1_instr =
     {
         .opcode = D3DSIO_MOV,
diff --git a/libs/vkd3d-shader/hlsl_sm4.c b/libs/vkd3d-shader/hlsl_sm4.c
index 6996bb2d..802db3c1 100644
--- a/libs/vkd3d-shader/hlsl_sm4.c
+++ b/libs/vkd3d-shader/hlsl_sm4.c
@@ -870,6 +870,8 @@ static void sm4_register_from_deref(struct hlsl_ctx *ctx, struct sm4_register *r
 
         if (hlsl_sm4_register_from_semantic(ctx, &var->semantic, false, &reg->type, swizzle_type, &has_idx))
         {
+            unsigned int offset = hlsl_offset_from_deref_safe(ctx, deref);
+
             if (has_idx)
             {
                 reg->idx[0] = var->semantic.index;
@@ -877,11 +879,11 @@ static void sm4_register_from_deref(struct hlsl_ctx *ctx, struct sm4_register *r
             }
 
             reg->dim = VKD3D_SM4_DIMENSION_VEC4;
-            *writemask = (1u << data_type->dimx) - 1;
+            *writemask = ((1u << data_type->dimx) - 1) << (offset % 4);
         }
         else
         {
-            struct hlsl_reg hlsl_reg = hlsl_reg_from_deref(ctx, deref, data_type);
+            struct hlsl_reg hlsl_reg = hlsl_reg_from_deref(ctx, deref);
 
             assert(hlsl_reg.allocated);
             reg->type = VKD3D_SM4_RT_INPUT;
@@ -899,6 +901,8 @@ static void sm4_register_from_deref(struct hlsl_ctx *ctx, struct sm4_register *r
 
         if (hlsl_sm4_register_from_semantic(ctx, &var->semantic, true, &reg->type, swizzle_type, &has_idx))
         {
+            unsigned int offset = hlsl_offset_from_deref_safe(ctx, deref);
+
             if (has_idx)
             {
                 reg->idx[0] = var->semantic.index;
@@ -909,11 +913,11 @@ static void sm4_register_from_deref(struct hlsl_ctx *ctx, struct sm4_register *r
                 reg->dim = VKD3D_SM4_DIMENSION_SCALAR;
             else
                 reg->dim = VKD3D_SM4_DIMENSION_VEC4;
-            *writemask = (1u << data_type->dimx) - 1;
+            *writemask = ((1u << data_type->dimx) - 1) << (offset % 4);
         }
         else
         {
-            struct hlsl_reg hlsl_reg = hlsl_reg_from_deref(ctx, deref, data_type);
+            struct hlsl_reg hlsl_reg = hlsl_reg_from_deref(ctx, deref);
 
             assert(hlsl_reg.allocated);
             reg->type = VKD3D_SM4_RT_OUTPUT;
@@ -925,7 +929,7 @@ static void sm4_register_from_deref(struct hlsl_ctx *ctx, struct sm4_register *r
     }
     else
     {
-        struct hlsl_reg hlsl_reg = hlsl_reg_from_deref(ctx, deref, data_type);
+        struct hlsl_reg hlsl_reg = hlsl_reg_from_deref(ctx, deref);
 
         assert(hlsl_reg.allocated);
         reg->type = VKD3D_SM4_RT_TEMP;