Cycles: Use XDG's .cache folder for cached kernels

Basically just moves cached kernels from ~/.config/blender/BLENDER_VERSION to
~/.cache/cycles/kernels. This has following benefits:

- Follows XDG specification more closely,
  not as if it's totally crucial or measurable by users, but still nice.

- Prevents unexpected sizes of config folder, makes disk space used in more
  predictable for users way.

- Allows to share kernels across multiple Blender versions,
  which makes it easier debugging at the times close to release.

- "Copy Previous Settings" operator will no longer be copying possibly
  gigabytes of cached kernels, which used to lead to really nast disk usage
  and annoying delays of copying settings.

- In the future we can have some smart logic to clear old unused cached
  kernels.

Currently only done for Linux and OSX. Windows still follows old "cache"
folder logic, but it's not really important for now because we don't
support kernel compilation on this platform yet.

Reviewers: dingto, juicyfruit, brecht

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D2197

intern/cycles/device/device_cuda.cpp

@@ -343,7 +343,7 @@ public:
 		const string cubin_file = string_printf("cycles_kernel_sm%d%d_%s.cubin",
 		                                        major, minor,
 		                                        cubin_md5.c_str());
-		const string cubin = path_user_get(path_join("cache", cubin_file));
+		const string cubin = path_cache_get(path_join("kernels", cubin_file));
 		VLOG(1) << "Testing for locally compiled kernel " << cubin << ".";
 		if(path_exists(cubin)) {
 			VLOG(1) << "Using locally compiled kernel.";

intern/cycles/device/device_opencl.cpp

@@ -987,7 +987,7 @@ public:
 			string clbin = string_printf("cycles_kernel_%s_%s.clbin",
 			                             device_md5.c_str(),
 			                             kernel_md5.c_str());
-			clbin = path_user_get(path_join("cache", clbin));
+			clbin = path_cache_get(path_join("kernels", clbin));
 
 			/* path to preprocessed source for debugging */
 			string clsrc, *debug_src = NULL;
@@ -996,7 +996,7 @@ public:
 				clsrc = string_printf("cycles_kernel_%s_%s.cl",
 				                      device_md5.c_str(),
 				                      kernel_md5.c_str());
-				clsrc = path_user_get(path_join("cache", clsrc));
+				clsrc = path_cache_get(path_join("kernels", clsrc));
 				debug_src = &clsrc;
 			}
 
@@ -1680,7 +1680,7 @@ public:
 			string clbin = string_printf("cycles_kernel_%s_%s.clbin",
 			                             device_md5.c_str(),
 			                             kernel_md5.c_str());
-			clbin = path_user_get(path_join("cache", clbin));
+			clbin = path_cache_get(path_join("kernels", clbin));
 
 			/* Path to preprocessed source for debugging. */
 			string clsrc, *debug_src = NULL;
@@ -1688,7 +1688,7 @@ public:
 				clsrc = string_printf("cycles_kernel_%s_%s.cl",
 				                      device_md5.c_str(),
 				                      kernel_md5.c_str());
-				clsrc = path_user_get(path_join("cache", clsrc));
+				clsrc = path_cache_get(path_join("kernels", clsrc));
 				debug_src = &clsrc;
 			}
 
@@ -2102,7 +2102,7 @@ public:
 			return false;
 		}
 
-		string cache_clbin = path_user_get(path_join("cache", clbin));
+		string cache_clbin = path_cache_get(path_join("kernels", clbin));
 
 		/* If exists already, try use it. */
 		if(path_exists(cache_clbin) && load_binary(kernel_path,
@@ -2220,7 +2220,7 @@ public:
 		if(opencl_kernel_use_debug()) { \
 			clsrc = string_printf("cycles_kernel_%s_%s_" #name ".cl", \
 			                      device_md5.c_str(), kernel_md5.c_str()); \
-			clsrc = path_user_get(path_join("cache", clsrc)); \
+			clsrc = path_cache_get(path_join("kernels", clsrc)); \
 			debug_src = &clsrc; \
 		} \
 		if(!load_split_kernel(#name, \

intern/cycles/util/util_path.cpp

@@ -36,6 +36,7 @@ OIIO_NAMESPACE_USING
 #else
 #  define DIR_SEP '/'
 #  include <dirent.h>
+#  include <pwd.h>
 #endif
 
 #ifdef HAVE_SHLWAPI_H
@@ -63,6 +64,7 @@ typedef struct stat path_stat_t;
 
 static string cached_path = "";
 static string cached_user_path = "";
+static string cached_xdg_cache_path = "";
 
 namespace {
 
@@ -331,6 +333,23 @@ static char *path_specials(const string& sub)
 	return NULL;
 }
 
+#if defined(__linux__) || defined(__APPLE__)
+static string path_xdg_cache_get()
+{
+	const char *home = getenv("XDG_CACHE_HOME");
+	if(home) {
+		return string(home);
+	}
+	else {
+		home = getenv("HOME");
+		if(home == NULL) {
+			home = getpwuid(getuid())->pw_dir;
+		}
+		return path_join(string(home), ".cache");
+	}
+}
+#endif
+
 void path_init(const string& path, const string& user_path)
 {
 	cached_path = path;
@@ -364,6 +383,24 @@ string path_user_get(const string& sub)
 	return path_join(cached_user_path, sub);
 }
 
+string path_cache_get(const string& sub)
+{
+#if defined(__linux__) || defined(__APPLE__)
+	if(cached_xdg_cache_path == "") {
+		cached_xdg_cache_path = path_xdg_cache_get();
+	}
+	string result = path_join(cached_xdg_cache_path, "cycles");
+	return path_join(result, sub);
+#else
+	/* TODO(sergey): What that should be on Windows? */
+	return path_user_get(path_join("cache", sub));
+#endif
+}
+
+#if defined(__linux__) || defined(__APPLE__)
+string path_xdg_home_get(const string& sub = "");
+#endif
+
 string path_filename(const string& path)
 {
 	size_t index = find_last_slash(path);

intern/cycles/util/util_path.h

@@ -35,6 +35,7 @@ CCL_NAMESPACE_BEGIN
 void path_init(const string& path = "", const string& user_path = "");
 string path_get(const string& sub = "");
 string path_user_get(const string& sub = "");
+string path_cache_get(const string& sub = "");
 
 /* path string manipulation */
 string path_filename(const string& path);