Index: docs/LangRef.rst =================================================================== --- docs/LangRef.rst +++ docs/LangRef.rst @@ -5192,6 +5192,68 @@ !0 = !{i32* @a} +'``prof``' Metadata +^^^^^^^^^^^^^^^^^^^ + +The ``prof`` metadata is used to record profile data in the IR. +The first operand of the metadata node indicates the profile metadata +type. There are currently 3 types: +:ref:`branch_weights`, +:ref:`function_entry_count`, and +:ref:`VP`. + +.. _prof_node_branch_weights: + +branch_weights +"""""""""""""" + +Branch weight metadata attached to a branch, select, switch or call instruction +represents the likeliness of the associated branch being taken. +For more information, see :doc:`BranchWeightMetadata`. + +.. _prof_node_function_entry_count: + +function_entry_count +"""""""""""""""""""" + +Function entry count metadata can be attached to function definitions +to record the number of times the function is called. Used with BFI +information, it is also used to derive the basic block profile count. +For more information, see :doc:`BranchWeightMetadata`. + +.. _prof_node_VP: + +VP +"" + +VP (value profile) metadata can be attached to instructions that have +value profile information. Currently this is indirect calls (where it +records the hottest callees) and calls to memory intrinsics such as memcpy, +memmove, and memset (where it records the hottest byte lengths). + +Each VP metadata node contains "VP" string, then a uint32_t value for the value +profiling kind, a uint64_t value for the total number of times the instruction +is executed, followed by uint64_t value and execution count pairs. +The value profiling kind is 0 for indirect call targets and 1 for memory +operations. For indirect call targets, each profile value is a hash +of the callee function name, and for memory operations each value is the +byte length. + +Indirect call example: + +.. code-block:: llvm + + call void %f(), !prof !1 + !1 = !{!"VP", i32 0, i64 1600, i64 7651369219802541373, i64 1030, i64 -4377547752858689819, i64 410} + +Note that the VP type is 0 (the second operand), which indicates this is +an indirect call value profile data. The third operand indicates that the +indirect call executed 1600 times. The 4th and 6th operands give the +hashes of the 2 hottest target functions' names (this is the same hash used +to represent function names in the profile database), and the 5th and 7th +operands give the execution count that each of the respective prior target +functions was called. + Module Flags Metadata =====================