[spirv][fuzz] Avoid remapping multiple entry point names

If the `remapped_entry_point_name` option is non-empty, we cannot
codegen a module with multiple entry points as they would all receive
the same name.

Note that this check will become unnecessary once we address
crbug.com/375388101.

Fixed: 384115680
Change-Id: I6fff79ed0f11b695bc89ef420bac07b31ef34221
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/219754
Commit-Queue: Antonio Maiorano <[email protected]>
Commit-Queue: James Price <[email protected]>
Reviewed-by: Antonio Maiorano <[email protected]>
Auto-Submit: James Price <[email protected]>

src/tint/lang/spirv/writer/writer_fuzz.cc

@@ -44,6 +44,18 @@ bool CanRun(const core::ir::Module& module, const Options& options) {
         if (options.remapped_entry_point_name.find('\0') != std::string::npos) {
             return false;
         }
+
+        // Check for multiple entry points.
+        // TODO(375388101): Remove this check when SingleEntryPoint is part of the backend.
+        bool has_entry_point = false;
+        for (auto& func : module.functions) {
+            if (func->IsEntryPoint()) {
+                if (has_entry_point) {
+                    return false;
+                }
+                has_entry_point = true;
+            }
+        }
     }
 
     // Check for unsupported module-scope variable address spaces and types.