From 8faf3ed95357002fdc53890d80c931784beb74eb Mon Sep 17 00:00:00 2001 From: Xiong Hu Luo Date: Thu, 10 Oct 2019 19:44:26 +0000 Subject: [PATCH] re PR middle-end/26241 (None of the IPA passes are documented in passes.texi) 2019-10-10 Xiong Hu Luo Sandra Loosemore gcc/ PR middle-end/26241 * doc/lto.texi (IPA): Reference to the IPA passes. * doc/passes.texi (Pass manager): Add node IPA passes and description for each IPA pass. Co-Authored-By: Sandra Loosemore From-SVN: r276851 --- gcc/ChangeLog | 8 ++ gcc/doc/lto.texi | 9 +- gcc/doc/passes.texi | 272 ++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 285 insertions(+), 4 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 6a86dd802b1..b9bcabae38a 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2019-10-10 Xiong Hu Luo + Sandra Loosemore + + PR middle-end/26241 + * doc/lto.texi (IPA): Reference to the IPA passes. + * doc/passes.texi (Pass manager): Add node IPA passes and + description for each IPA pass. + 2019-10-10 Jan Hubicka * ipa-reference.c: Do not include splay-tree.h diff --git a/gcc/doc/lto.texi b/gcc/doc/lto.texi index 771e8278e50..09f0184e6a8 100644 --- a/gcc/doc/lto.texi +++ b/gcc/doc/lto.texi @@ -350,10 +350,11 @@ while the @emph{Read summary}, @emph{Execute}, and @end itemize To simplify development, the GCC pass manager differentiates -between normal inter-procedural passes and small inter-procedural -passes. A @emph{small inter-procedural pass} -(@code{SIMPLE_IPA_PASS}) is a pass that does -everything at once and thus it cannot be executed during WPA in +between normal inter-procedural passes (@pxref{Regular IPA passes}), +small inter-procedural passes (@pxref{Small IPA passes}) +and late inter-procedural passes (@pxref{Late IPA passes}). +A small or late IPA pass (@code{SIMPLE_IPA_PASS}) does +everything at once and thus cannot be executed during WPA in WHOPR mode. It defines only the @emph{Execute} stage and during this stage it accesses and modifies the function bodies. Such passes are useful for optimization at LGEN or LTRANS time and are diff --git a/gcc/doc/passes.texi b/gcc/doc/passes.texi index 6edb9a0bfb7..889fa0f9004 100644 --- a/gcc/doc/passes.texi +++ b/gcc/doc/passes.texi @@ -20,6 +20,7 @@ where near complete. * Parsing pass:: The language front end turns text into bits. * Gimplification pass:: The bits are turned into something we can optimize. * Pass manager:: Sequencing the optimization passes. +* IPA passes:: Inter-procedural optimizations. * Tree SSA passes:: Optimizations on a high-level representation. * RTL passes:: Optimizations on a low-level representation. * Optimization info:: Dumping optimization information from passes. @@ -178,6 +179,277 @@ TODO: describe the global variables set up by the pass manager, and a brief description of how a new pass should use it. I need to look at what info RTL passes use first@enddots{} +@node IPA passes +@section Inter-procedural optimization passes +@cindex IPA passes +@cindex inter-procedural optimization passes + +The inter-procedural optimization (IPA) passes use call graph +information to perform transformations across function boundaries. +IPA is a critical part of link-time optimization (LTO) and +whole-program (WHOPR) optimization, and these passes are structured +with the needs of LTO and WHOPR in mind by dividing their operations +into stages. For detailed discussion of the LTO/WHOPR IPA pass stages +and interfaces, see @ref{IPA}. + +The following briefly describes the inter-procedural optimization (IPA) +passes, which are split into small IPA passes, regular IPA passes, +and late IPA passes, according to the LTO/WHOPR processing model. + +@menu +* Small IPA passes:: +* Regular IPA passes:: +* Late IPA passes:: +@end menu + +@node Small IPA passes +@subsection Small IPA passes +@cindex small IPA passes +A small IPA pass is a pass derived from @code{simple_ipa_opt_pass}. +As described in @ref{IPA}, it does everything at once and +defines only the @emph{Execute} stage. During this +stage it accesses and modifies the function bodies. +No @code{generate_summary}, @code{read_summary}, or @code{write_summary} +hooks are defined. + +@itemize @bullet +@item IPA free lang data + +This pass frees resources that are used by the front end but are +not needed once it is done. It is located in @file{tree.c} and is described by +@code{pass_ipa_free_lang_data}. + +@item IPA function and variable visibility + +This is a local function pass handling visibilities of all symbols. This +happens before LTO streaming, so @option{-fwhole-program} should be ignored +at this level. It is located in @file{ipa-visibility.c} and is described by +@code{pass_ipa_function_and_variable_visibility}. + +@item IPA remove symbols + +This pass performs reachability analysis and reclaims all unreachable nodes. +It is located in @file{passes.c} and is described by +@code{pass_ipa_remove_symbols}. + +@item IPA OpenACC + +This is a pass group for OpenACC processing. It is located in +@file{tree-ssa-loop.c} and is described by @code{pass_ipa_oacc}. + +@item IPA points-to analysis + +This is a tree-based points-to analysis pass. The idea behind this analyzer +is to generate set constraints from the program, then solve the resulting +constraints in order to generate the points-to sets. It is located in +@file{tree-ssa-structalias.c} and is described by @code{pass_ipa_pta}. + +@item IPA OpenACC kernels + +This is a pass group for processing OpenACC kernels regions. It is a +subpass of the IPA OpenACC pass group that runs on offloaded functions +containing OpenACC kernels loops. It is located in +@file{tree-ssa-loop.c} and is described by +@code{pass_ipa_oacc_kernels}. + +@item Target clone + +This is a pass for parsing functions with multiple target attributes. +It is located in @file{multiple_target.c} and is described by +@code{pass_target_clone}. + +@item IPA auto profile + +This pass uses AutoFDO profiling data to annotate the control flow graph. +It is located in @file{auto-profile.c} and is described by +@code{pass_ipa_auto_profile}. + +@item IPA tree profile + +This pass does profiling for all functions in the call graph. +It calculates branch +probabilities and basic block execution counts. It is located +in @file{tree-profile.c} and is described by @code{pass_ipa_tree_profile}. + +@item IPA free function summary + +This pass is a small IPA pass when argument @code{small_p} is true. +It releases inline function summaries and call summaries. +It is located in @file{ipa-fnsummary.c} and is described by +@code{pass_ipa_free_free_fn_summary}. + +@item IPA increase alignment + +This pass increases the alignment of global arrays to improve +vectorization. It is located in @file{tree-vectorizer.c} +and is described by @code{pass_ipa_increase_alignment}. + +@item IPA transactional memory + +This pass is for transactional memory support. +It is located in @file{trans-mem.c} and is described by +@code{pass_ipa_tm}. + +@item IPA lower emulated TLS + +This pass lowers thread-local storage (TLS) operations +to emulation functions provided by libgcc. +It is located in @file{tree-emutls.c} and is described by +@code{pass_ipa_lower_emutls}. + +@end itemize + +@node Regular IPA passes +@subsection Regular IPA passes +@cindex regular IPA passes + +A regular IPA pass is a pass derived from @code{ipa_opt_pass_d} that +is executed in WHOPR compilation. Regular IPA passes may have summary +hooks implemented in any of the LGEN, WPA or LTRANS stages (@pxref{IPA}). + +@itemize @bullet +@item IPA whole program visibility + +This pass performs various optimizations involving symbol visibility +with @option{-fwhole-program}, including symbol privatization, +discovering local functions, and dismantling comdat groups. It is +located in @file{ipa-visibility.c} and is described by +@code{pass_ipa_whole_program_visibility}. + +@item IPA profile + +The IPA profile pass propagates profiling frequencies across the call +graph. It is located in @file{ipa-profile.c} and is described by +@code{pass_ipa_profile}. + +@item IPA identical code folding + +This is the inter-procedural identical code folding pass. +The goal of this transformation is to discover functions +and read-only variables that have exactly the same semantics. It is +located in @file{ipa-icf.c} and is described by @code{pass_ipa_icf}. + +@item IPA devirtualization + +This pass performs speculative devirtualization based on the type +inheritance graph. When a polymorphic call has only one likely target +in the unit, it is turned into a speculative call. It is located in +@file{ipa-devirt.c} and is described by @code{pass_ipa_devirt}. + +@item IPA constant propagation + +The goal of this pass is to discover functions that are always invoked +with some arguments with the same known constant values and to modify +the functions accordingly. It can also do partial specialization and +type-based devirtualization. It is located in @file{ipa-cp.c} and is +described by @code{pass_ipa_cp}. + +@item IPA scalar replacement of aggregates + +This pass can replace an aggregate parameter with a set of other parameters +representing part of the original, turning those passed by reference +into new ones which pass the value directly. It also removes unused +function return values and unused function parameters. This pass is +located in @file{ipa-sra.c} and is described by @code{pass_ipa_sra}. + +@item IPA constructor/destructor merge + +This pass merges multiple constructors and destructors for static +objects into single functions. It's only run at LTO time unless the +target doesn't support constructors and destructors natively. The +pass is located in @file{ipa.c} and is described by +@code{pass_ipa_cdtor_merge}. + +@item IPA HSA + +This pass is part of the GCC support for HSA (Heterogeneous System +Architecture) accelerators. It is responsible for creation of HSA +clones and emitting HSAIL instructions for them. It is located in +@file{ipa-hsa.c} and is described by @code{pass_ipa_hsa}. + +@item IPA function summary + +This pass provides function analysis for inter-procedural passes. +It collects estimates of function body size, execution time, and frame +size for each function. It also estimates information about function +calls: call statement size, time and how often the parameters change +for each call. It is located in @file{ipa-fnsummary.c} and is +described by @code{pass_ipa_fn_summary}. + +@item IPA inline + +The IPA inline pass handles function inlining with whole-program +knowledge. Small functions that are candidates for inlining are +ordered in increasing badness, bounded by unit growth parameters. +Unreachable functions are removed from the call graph. Functions called +once and not exported from the unit are inlined. This pass is located in +@file{ipa-inline.c} and is described by @code{pass_ipa_inline}. + +@item IPA pure/const analysis + +This pass marks functions as being either const (@code{TREE_READONLY}) or +pure (@code{DECL_PURE_P}). The per-function information is produced +by @code{pure_const_generate_summary}, then the global information is computed +by performing a transitive closure over the call graph. It is located in +@file{ipa-pure-const.c} and is described by @code{pass_ipa_pure_const}. + +@item IPA free function summary + +This pass is a regular IPA pass when argument @code{small_p} is false. +It releases inline function summaries and call summaries. +It is located in @file{ipa-fnsummary.c} and is described by +@code{pass_ipa_free_fn_summary}. + +@item IPA reference + +This pass gathers information about how variables whose scope is +confined to the compilation unit are used. It is located in +@file{ipa-reference.c} and is described by @code{pass_ipa_reference}. + +@item IPA single use + +This pass checks whether variables are used by a single function. +It is located in @file{ipa.c} and is described by +@code{pass_ipa_single_use}. + +@item IPA comdats + +This pass looks for static symbols that are used exclusively +within one comdat group, and moves them into that comdat group. It is +located in @file{ipa-comdats.c} and is described by +@code{pass_ipa_comdats}. + +@end itemize + +@node Late IPA passes +@subsection Late IPA passes +@cindex late IPA passes + +Late IPA passes are simple IPA passes executed after +the regular passes. In WHOPR mode the passes are executed after +partitioning and thus see just parts of the compiled unit. + +@itemize @bullet +@item Materialize all clones + +Once all functions from compilation unit are in memory, produce all clones +and update all calls. It is located in @file{ipa.c} and is described by +@code{pass_materialize_all_clones}. + +@item IPA points-to analysis + +Points-to analysis; this is the same as the points-to-analysis pass +run with the small IPA passes (@pxref{Small IPA passes}). + +@item OpenMP simd clone + +This is the OpenMP constructs' SIMD clone pass. It creates the appropriate +SIMD clones for functions tagged as elemental SIMD functions. +It is located in @file{omp-simd-clone.c} and is described by +@code{pass_omp_simd_clone}. + +@end itemize + @node Tree SSA passes @section Tree SSA passes -- 2.30.2