libs/vkd3d: Add VKD3D_SHADER_DUMP_PATH environment variable for dumping shaders.

A similar functionality was helpful numerous number of times when
developing libvkd3d-shader.

libs/vkd3d/state.c

@@ -19,6 +19,8 @@
 
 #include "vkd3d_private.h"
 
+#include <stdio.h>
+
 /* ID3D12RootSignature */
 static inline struct d3d12_root_signature *impl_from_ID3D12RootSignature(ID3D12RootSignature *iface)
 {
@@ -1190,6 +1192,70 @@ struct d3d12_pipeline_state *unsafe_impl_from_ID3D12PipelineState(ID3D12Pipeline
     return impl_from_ID3D12PipelineState(iface);
 }
 
+static void dump_shader(const char *path, const char *prefix, const void *data, size_t size)
+{
+    static unsigned int shader_id = 0;
+    char filename[1024];
+    FILE *f;
+
+    snprintf(filename, ARRAY_SIZE(filename), "%s/vkd3d-shader-%s-%u.dxbc", path, prefix, shader_id);
+    if (!(f = fopen(filename, "wb")))
+    {
+        ERR("Failed to open %s for dumping shader.\n", filename);
+        return;
+    }
+
+    if (fwrite(data, 1, size, f) != size)
+        ERR("Failed to write shader to %s.\n", filename);
+    if (fclose(f))
+        ERR("Failed to close stream %s.\n", filename);
+
+    ++shader_id;
+}
+
+static void dump_shader_stage(VkShaderStageFlagBits stage, const void *data, size_t size)
+{
+    static bool enabled = true;
+    const char *prefix;
+    const char *path;
+
+    if (!enabled)
+        return;
+
+    if (!(path = getenv("VKD3D_SHADER_DUMP_PATH")))
+    {
+        enabled = false;
+        return;
+    }
+
+    switch (stage)
+    {
+        case VK_SHADER_STAGE_VERTEX_BIT:
+            prefix = "vs";
+            break;
+        case VK_SHADER_STAGE_TESSELLATION_CONTROL_BIT:
+            prefix = "hs";
+            break;
+        case VK_SHADER_STAGE_TESSELLATION_EVALUATION_BIT:
+            prefix = "ds";
+            break;
+        case VK_SHADER_STAGE_GEOMETRY_BIT:
+            prefix = "gs";
+            break;
+        case VK_SHADER_STAGE_FRAGMENT_BIT:
+            prefix = "ps";
+            break;
+        case VK_SHADER_STAGE_COMPUTE_BIT:
+            prefix = "cs";
+            break;
+        default:
+            prefix = "unk";
+            break;
+    }
+
+    dump_shader(path, prefix, data, size);
+}
+
 static HRESULT create_shader_stage(struct d3d12_device *device,
         struct VkPipelineShaderStageCreateInfo *stage_desc, enum VkShaderStageFlagBits stage,
         const D3D12_SHADER_BYTECODE *code, const struct vkd3d_shader_interface *shader_interface)
@@ -1212,6 +1278,7 @@ static HRESULT create_shader_stage(struct d3d12_device *device,
     shader_desc.pNext = NULL;
     shader_desc.flags = 0;
 
+    dump_shader_stage(stage, code->pShaderBytecode, code->BytecodeLength);
     if (FAILED(hr = vkd3d_shader_compile_dxbc(&dxbc, &spirv, 0, shader_interface)))
     {
         WARN("Failed to compile shader, hr %#x.\n", hr);