Merge pull request #131 from frasercrmck/sub-group-analysis-clarify

[compiler] Clarify semantics of SubgroupAnalysis pass

Author: frasercrmck

modules/compiler/test/lit/passes/sub-group-analysis.ll

@@ -67,7 +67,22 @@ exit:
   ret void
 }
 
+; We don't consider any of the internal mux 'setters' as uses of sub-group
+; builtins, as they are purely there to support the framework and aren't
+; apparent to the user.
+; CHECK: Function 'function4' uses no sub-group builtins
+define spir_func void @function4() {
+  call void @__mux_set_sub_group_id(i32 0)
+  call void @__mux_set_num_sub_groups(i32 1)
+  call void @__mux_set_max_sub_group_size(i32 2)
+  ret void
+}
+
 declare i32 @__mux_get_sub_group_id()
 declare i32 @__mux_get_sub_group_local_id()
 declare i32 @__mux_sub_group_shuffle_i32(i32, i32)
 declare i32 @__mux_get_max_sub_group_size()
+
+declare void @__mux_set_sub_group_id(i32)
+declare void @__mux_set_num_sub_groups(i32)
+declare void @__mux_set_max_sub_group_size(i32)

modules/compiler/utils/include/compiler/utils/sub_group_analysis.h

@@ -34,6 +34,10 @@ namespace utils {
 /// processed. Thus an external function declaration that uses sub-group
 /// builtins will be missed.
 ///
+/// Internal mux sub-group 'setter' functions are not counted. This is because
+/// they only used internally by the oneAPI Construction Kit as scaffolding for
+/// the sub-group support that the user can observe.
+///
 /// Each function contains the set of mux sub-group builtins it (transitively)
 /// calls.
 class GlobalSubgroupInfo {