[patch, doc] documenting new options

Olga Golovanevsky OLGA@il.ibm.com
Thu Dec 6 14:16:00 GMT 2007

This patch documents recently committed struct-reorg optimization,
i.e. -fipa-struct-reorg option and struct-reorg-cold-struct-ratio

Any comments? Ok for mainline?



2007-12-06  Olga Golovanevsky  <olga@il.ibm.com>

      * doc/invoke.texi (Optimize Options): Document new -fipa-struct-reorg
      option and struct-reorg-cold-struct-ratio parameter.

Index: invoke.texi
--- invoke.texi   (revision 130578)
+++ invoke.texi   (working copy)
@@ -329,13 +329,13 @@ Objective-C and Objective-C++ Dialects}.
 -fgcse-sm -fif-conversion -fif-conversion2 -finline-functions @gol
 -finline-functions-called-once -finline-limit=@var{n} @gol
 -finline-small-functions -fipa-pta -fipa-pure-const -fipa-reference @gol
--fipa-type-escape -fivopts -fkeep-inline-functions -fkeep-static-consts
--fmerge-all-constants -fmerge-constants -fmodulo-sched @gol
--fmodulo-sched-allow-regmoves -fmove-loop-invariants -fmudflap @gol
--fmudflapir -fmudflapth -fno-branch-count-reg -fno-default-inline @gol
--fno-defer-pop -fno-function-cse -fno-guess-branch-probability @gol
--fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol
--fno-sched-interblock -fno-sched-spec -fno-signed-zeros @gol
+-fipa-struct-reorg -fipa-type-escape -fivopts -fkeep-inline-functions @gol
+-fkeep-static-consts -fmerge-all-constants -fmerge-constants @gol
+-fmodulo-sched -fmodulo-sched-allow-regmoves -fmove-loop-invariants @gol
+-fmudflap -fmudflapir -fmudflapth -fno-branch-count-reg @gol
+-fno-default-inline -fno-defer-pop -fno-function-cse @gol
+-fno-guess-branch-probability -fno-inline -fno-math-errno -fno-peephole
+-fno-peephole2 -fno-sched-interblock -fno-sched-spec -fno-signed-zeros
 -fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol
 -fomit-frame-pointer -foptimize-register-move -foptimize-sibling-calls
 -fpeel-loops -fpredictive-commoning -fprefetch-loop-arrays @gol
@@ -5711,6 +5711,20 @@ Discover which static variables do not e
 compilation unit.
 Enabled by default at @option{-O} and higher.

+@item -fipa-struct-reorg
+@opindex fipa-struct-reorg
+Perform structure reorganization optimization, that change C-like
+layout in order to better utilize spatial locality. Effective for programs
+containing arrays of structures. Available in two compilation modes:
+profile-based, as with @option{-fprofile-generate} and @option
+or static. Require @option{-fipa-type-escape} to provide the safety of
+transformations. Work as whole program optimization, i.e. require
+@option{-fwhole-program} and @option{-combine} flags. Cold structures
+can remain intact through
+@option{--param struct-reorg-cold-struct-ratio=@var{value}} option.
+With this flag, the program debug info reflects a new structure layout.
 @item -fipa-pta
 @opindex fipa-pta
 Perform interprocedural pointer analysis.
@@ -6624,6 +6638,13 @@ of bytes in instantiated fields to the n
 structure exceeds this parameter, then block copies are not used.  The.
 default is 75.

+@item struct-reorg-cold-struct-ratio
+The threshold ratio between current and hotest structure counts
+used by @option{-fipa-struct-reorg}. We say that if the ratio of
+the current structure count, calculated by profiling, to the hotest
+structure count in the program is less than this parameter, then
+structure reorganization is not applied. The default is 10.
 @item max-crossjump-edges
 The maximum number of incoming edges to consider for crossjumping.
 The algorithm used by @option{-fcrossjumping} is @math{O(N^2)} in.

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