diff --git a/include/private/vkd3d_common.h b/include/private/vkd3d_common.h
index c696f885..1ac8a63b 100644
--- a/include/private/vkd3d_common.h
+++ b/include/private/vkd3d_common.h
@@ -23,6 +23,8 @@
 #include "vkd3d_windows.h"
 
 #include <ctype.h>
+#include <limits.h>
+#include <stdbool.h>
 
 #ifndef ARRAY_SIZE
 # define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
@@ -58,6 +60,21 @@ static inline unsigned int vkd3d_popcount(unsigned int v)
 #endif
 }
 
+static inline bool vkd3d_bitmask_is_contiguous(unsigned int mask)
+{
+    unsigned int i, j;
+
+    for (i = 0, j = 0; i < sizeof(mask) * CHAR_BIT; ++i)
+    {
+        if (mask & (1u << i))
+            ++j;
+        else if (j)
+            break;
+    }
+
+    return vkd3d_popcount(mask) == j;
+}
+
 /* Undefined for x == 0. */
 static inline unsigned int vkd3d_log2i(unsigned int x)
 {
diff --git a/libs/vkd3d-shader/spirv.c b/libs/vkd3d-shader/spirv.c
index ee409539..f17c7fa1 100644
--- a/libs/vkd3d-shader/spirv.c
+++ b/libs/vkd3d-shader/spirv.c
@@ -3807,22 +3807,6 @@ static uint32_t vkd3d_dxbc_compiler_emit_builtin_variable(struct vkd3d_dxbc_comp
     return id;
 }
 
-static bool vkd3d_write_mask_is_contiguous(unsigned int mask)
-{
-    unsigned int i, j;
-
-    assert(mask);
-    for (i = 0, j = 0; i < VKD3D_VEC4_SIZE; ++i)
-    {
-        if (mask & (1u << i))
-            ++j;
-        else if (j)
-            break;
-    }
-
-    return vkd3d_write_mask_component_count(mask) == j;
-}
-
 static bool needs_private_io_variable(const struct vkd3d_shader_signature *signature,
         unsigned int reg_idx, const struct vkd3d_spirv_builtin *builtin,
         unsigned int *component_count, unsigned int *out_write_mask)
@@ -3854,7 +3838,7 @@ static bool needs_private_io_variable(const struct vkd3d_shader_signature *signa
     if (builtin || have_sysval)
         return true;
 
-    if (!vkd3d_write_mask_is_contiguous(write_mask))
+    if (!vkd3d_bitmask_is_contiguous(write_mask))
     {
         FIXME("Write mask %#x is non-contiguous.\n", write_mask);
         return true;
diff --git a/tests/vkd3d_common.c b/tests/vkd3d_common.c
index 379c8b06..85f17161 100644
--- a/tests/vkd3d_common.c
+++ b/tests/vkd3d_common.c
@@ -43,7 +43,78 @@ static void test_parse_version(void)
     check_version("2.3.0", 2, 3);
 }
 
+static void check_contiguous(uint32_t mask, bool expected_result)
+{
+    bool r = vkd3d_bitmask_is_contiguous(mask);
+    ok(r == expected_result, "Got %#x for bitmask %#"PRIx32".\n", r, mask);
+}
+
+static void test_bitmask_is_contiguous(void)
+{
+    check_contiguous(0x00000000, true);
+
+    check_contiguous(0x00000001, true);
+    check_contiguous(0x00000002, true);
+    check_contiguous(0x00000003, true);
+    check_contiguous(0x00000004, true);
+    check_contiguous(0x00000005, false);
+    check_contiguous(0x00000006, true);
+    check_contiguous(0x00000007, true);
+    check_contiguous(0x00000008, true);
+    check_contiguous(0x00000009, false);
+    check_contiguous(0x0000000a, false);
+    check_contiguous(0x0000000b, false);
+    check_contiguous(0x0000000c, true);
+    check_contiguous(0x0000000d, false);
+    check_contiguous(0x0000000e, true);
+    check_contiguous(0x0000000f, true);
+
+    check_contiguous(0x10000000, true);
+    check_contiguous(0x20000000, true);
+    check_contiguous(0x30000000, true);
+    check_contiguous(0x40000000, true);
+    check_contiguous(0x50000000, false);
+    check_contiguous(0x60000000, true);
+    check_contiguous(0x70000000, true);
+    check_contiguous(0x80000000, true);
+    check_contiguous(0x90000000, false);
+    check_contiguous(0xa0000000, false);
+    check_contiguous(0xb0000000, false);
+    check_contiguous(0xc0000000, true);
+    check_contiguous(0xd0000000, false);
+    check_contiguous(0xe0000000, true);
+    check_contiguous(0xf0000000, true);
+
+    check_contiguous(0xf000000f, false);
+    check_contiguous(0x0f0000f0, false);
+    check_contiguous(0x00f00f00, false);
+
+    check_contiguous(0x000000ff, true);
+    check_contiguous(0x00000ff0, true);
+    check_contiguous(0x0000ff00, true);
+    check_contiguous(0x000ff000, true);
+    check_contiguous(0x00ff0000, true);
+    check_contiguous(0xff000000, true);
+
+    check_contiguous(0xfff00000, true);
+    check_contiguous(0xffff0000, true);
+    check_contiguous(0xffff0000, true);
+    check_contiguous(0xfffff000, true);
+    check_contiguous(0xffffff00, true);
+    check_contiguous(0xfffffff0, true);
+    check_contiguous(0xffffffff, true);
+
+    check_contiguous(0x0000001c, true);
+    check_contiguous(0x000001c0, true);
+    check_contiguous(0x00001c00, true);
+    check_contiguous(0x0001c000, true);
+    check_contiguous(0x001c0000, true);
+    check_contiguous(0x01c00000, true);
+    check_contiguous(0x1c000000, true);
+}
+
 START_TEST(vkd3d_common)
 {
     run_test(test_parse_version);
+    run_test(test_bitmask_is_contiguous);
 }