Hi,

This patch implements the fine-graind AutoFDO optimizations for GCC.
It uses linux perf to collect sample profiles, and uses debug info to
represent the profile. In GCC, it uses the profile to annotate CFG to
drive FDO. This can bring 50% to 110% of the speedup derived by
traditional instrumentation based FDO. (Average is between 70% to 80%
for many CPU intensive applications). Comparing with traditional FDO,
AutoFDO does not require instrumentation. It just need to have an
optimized binary with debug info to collect the profile.

This patch has passed bootstrap and gcc regression tests as well as
tested with crosstool. Okay for google branches?

If people in up-stream find this feature interesting, I'll spend some
time to port this to trunk and try to opensource the tool to generate
profile data file.

Dehao

The patch can also be viewed from:

http://codereview.appspot.com/6567079

gcc/ChangeLog.google-4_7:
2012-09-28  Dehao Chen  <dehao@dehao.com>

* cgraphbuild.c (build_cgraph_edges): Handle AutoFDO profile.
(rebuild_cgraph_edges): Likewise.
* cgraph.c (cgraph_clone_node): Likewise.
(clone_function_name): Likewise.
* cgraph.h (cgraph_node): New field.
* tree-pass.h (pass_ipa_auto_profile): New pass.
* cfghooks.c (make_forwarder_block): Handle AutoFDO profile.
* ipa-inline-transform.c (clone_inlined_nodes): Likewise.
* toplev.c (compile_file): Likewise.
(process_options): Likewise.
* debug.h (auto_profile_debug_hooks): New.
* cgraphunit.c (cgraph_finalize_compilation_unit): Handle AutoFDO
profile.
(cgraph_copy_node_for_versioning): Likewise.
* regs.h (REG_FREQ_FROM_BB): Likewise.
* gcov-io.h: (GCOV_TAG_AFDO_FILE_NAMES): New.
(GCOV_TAG_AFDO_FUNCTION): New.
(GCOV_TAG_AFDO_MODULE_GROUPING): New.
* ira-int.h (REG_FREQ_FROM_EDGE_FREQ): Handle AutoFDO profile.
* ipa-inline.c (edge_hot_enough_p): Likewise.
(edge_badness): Likewise.
(inline_small_functions): Likewise.
* dwarf2out.c (auto_profile_debug_hooks): New.
* opts.c (common_handle_option): Handle AutoFDO profile.
* timevar.def (TV_IPA_AUTOFDO): New.
* predict.c (compute_function_frequency): Handle AutoFDO profile.
(rebuild_frequencies): Handle AutoFDO profile.
* auto-profile.c (struct gcov_callsite_pos): New.
(struct gcov_callsite): New.
(struct gcov_stack): New.
(struct gcov_function): New.
(struct afdo_bfd_name): New.
(struct afdo_module): New.
(afdo_get_filename): New.
(afdo_get_original_name_size): New.
(afdo_get_bfd_name): New.
(afdo_read_bfd_names): New.
(afdo_stack_hash): New.
(afdo_stack_eq): New.
(afdo_function_hash): New.
(afdo_function_eq): New.
(afdo_bfd_name_hash): New.
(afdo_bfd_name_eq): New.
(afdo_bfd_name_del): New.
(afdo_module_hash): New.
(afdo_module_eq): New.
(afdo_module_num_strings): New.
(afdo_add_module): New.
(read_aux_modules): New.
(get_inline_stack_size_by_stmt): New.
(get_inline_stack_size_by_edge): New.
(get_function_name_from_block): New.
(get_inline_stack_by_stmt): New.
(get_inline_stack_by_edge): New.
(afdo_get_function_count): New.
(afdo_set_current_function_count): New.
(afdo_add_bfd_name_mapping): New.
(afdo_add_copy_scale): New.
(get_stack_count): New.
(get_stmt_count): New.
(afdo_get_callsite_count): New.
(afdo_get_bb_count): New.
(afdo_annotate_cfg): New.
(read_profile): New.
(process_auto_profile): New.
(init_auto_profile): New.
(end_auto_profile): New.
(afdo_find_equiv_class): New.
(afdo_propagate_single_edge): New.
(afdo_propagate_multi_edge): New.
(afdo_propagate_circuit): New.
(afdo_propagate): New.
(afdo_calculate_branch_prob): New.
(auto_profile): New.
(gate_auto_profile_ipa): New.
(struct simple_ipa_opt_pass): New.
* auto-profile.h (init_auto_profile): New.
(end_auto_profile): New.
(process_auto_profile): New.
(afdo_set_current_function_count): New.
(afdo_add_bfd_name_mapping): New.
(afdo_add_copy_scale): New.
(afdo_calculate_branch_prob): New.
(afdo_get_callsite_count): New.
(afdo_get_bb_count): New.
* profile.c (compute_branch_probabilities): Handle AutoFDO profile.
(branch_prob): Likeise.
* loop-unroll.c (decide_unroll_runtime_iterations): Likewise.
* coverage.c (coverage_init): Likewise.
* tree-ssa-live.c (remove_unused_scope_block_p): Likewise.
* common.opt (fauto-profile): New.
* tree-inline.c (copy_bb): Handle AutoFDO profile.
(copy_edges_for_bb): Likewise.
(copy_cfg_body): Likewise.
* tree-profile.c (direct_call_profiling): Likewise.
(gate_tree_profile_ipa): Likewise.
* basic-block.h (EDGE_ANNOTATED): New field.
(BB_ANNOTATED): New field.
* tree-cfg.c (gimple_merge_blocks): Handle AutoFDO profile.
* passes.c (init_optimization_passes): Handle AutoFDO profile.