fix: Include entry layer name in PTX cache key (#1954)

The ptx cache key introduced in #1938 didn't include a shader's entry layer name in its cache key. The direct callable function generated during llvm construction includes this layer name, so we could get false positive cache hits when two identical networks with matching group names had different entry layer names. The end result is an optix compilation error. This PR extends the cache key to handle this scenario.

Signed-off-by: Chris Hellmuth <chellmuth@gmail.com>

Author: chellmuth

src/liboslexec/instance.cpp

@@ -857,10 +857,14 @@ ShaderGroup::generate_optix_cache_key(string_view code)
     safegroup = Strutil::replace(name(), "/", "_", true);
     safegroup = Strutil::replace(safegroup, ":", "_", true);
 
-    // Cache key includes the groupname in addition to the serialized IR.
-    // This is because the groupname makes its way into the ptx's direct callable name,
-    // but isn't included in the serialization.
-    std::string cache_key = fmtformat("cache-osl-ptx-{}-{}", safegroup, ir_key);
+    ShaderInstance* inst = layer(nlayers() - 1);
+    ustring layername    = inst->layername();
+
+    // Cache key includes group and entry layer names in addition to the serialized IR.
+    // This is because the group and layer names make their way into the ptx's
+    // direct callable name, but isn't included in the serialization.
+    std::string cache_key = fmtformat("cache-osl-ptx-{}-{}-{}", safegroup,
+                                      layername, ir_key);
 
     m_optix_cache_key = cache_key;
 }