Mesa calculates a sha1 based on some things they reason affect the output, but likely it is not truely a function of every parameter than can make a difference to the shader output. When we updated from llvm6 to lvm7 I'm guessing it changed the shaders somehow, and the llvm version is not included in the hash. Since I have zero understanding mesa, I'm not capable of determining the best solution. One thought is that if we included the mesa /gnu/store path in the calculation, this would make the hash's truely unique for a given mesa version, but also cached shaders that /would/ work would be routinely discarded after an update (i assume?). Would this be sensible or completely break something else? Should we just add the llvm version, or just start a mesa bug report asking for input?
The code:
ralloc_asprintf_append(&buf, "tf: %d ", prog->TransformFeedback.BufferMode);
for (unsigned int i = 0; i < prog->TransformFeedback.NumVarying; i++) {
ralloc_asprintf_append(&buf, "%s ",
prog->TransformFeedback.VaryingNames[i]);
}
/* SSO has an effect on the linked program so include this when
generating
* the sha also. */ ralloc_asprintf_append(&buf, "sso: %s\n", prog->SeparateShader ? "T" : "F");/* A shader might end up producing different output depending on the glsl * version supported by the compiler. For example a different path might be
* taken by the preprocessor, so add the version to the hash input.
*/
ralloc_asprintf_append(&buf, "api: %d glsl: %d fglsl: %d\n",
ctx->API, ctx->Const.GLSLVersion,
ctx->Const.ForceGLSLVersion);
/* We run the preprocessor on shaders after hashing them, so we need to
* add any extension override vars to the hash. If we don't do this the
* preprocessor could result in different output and we could load the
* wrong shader.
*/
char *ext_override = getenv("MESA_EXTENSION_OVERRIDE");
if (ext_override) {
ralloc_asprintf_append(&buf, "ext:%s", ext_override);
}
/* DRI config options may also change the output from the compiler so
* include them as an input to sha1 creation.
*/
char sha1buf[41];
_mesa_sha1_format(sha1buf, ctx->Const.dri_config_options_sha1);
ralloc_strcat(&buf, sha1buf);
for (unsigned i = 0; i < prog->NumShaders; i++) {
struct gl_shader *sh = prog->Shaders[i];
_mesa_sha1_format(sha1buf, sh->sha1);
ralloc_asprintf_append(&buf, "%s: %s\n",
_mesa_shader_stage_to_abbrev(sh->Stage), sha1buf);
