bb-reorder: Documentation updates

2015-09-23   Segher Boessenkool  <segher@kernel.crashing.org>

	* doc/invoke.texi (Optimization Options): Add
	-freorder-blocks-algorithm=.
	(Optimize Options) <-O>: Add -freorder-blocks.
	<-O2>: Remove -freorder-blocks.  Add -freorder-blocks-algorithm=stc.
	<-Os>: Add -freorder-blocks-algorithm=stc as not enabled.
	<-freorder-blocks>: Also enabled at levels -O and -Os.
	<-freorder-blocks-algorithm=>: Document new option.

From-SVN: r228319

gcc/ChangeLog

 2015-10-01  Segher Boessenkool  <segher@kernel.crashing.org>
 
+	* doc/invoke.texi (Optimization Options): Add
+	-freorder-blocks-algorithm=.
+	(Optimize Options) <-O>: Add -freorder-blocks.
+	<-O2>: Remove -freorder-blocks.  Add -freorder-blocks-algorithm=stc.
+	<-Os>: Add -freorder-blocks-algorithm=stc as not enabled.
+	<-freorder-blocks>: Also enabled at levels -O and -Os.
+	<-freorder-blocks-algorithm=>: Document new option.
+
+2015-10-01  Segher Boessenkool  <segher@kernel.crashing.org>
+
 	* bb-reorder.c (reorder_basic_blocks): Use the algorithm selected
 	with flag_reorder_blocks_algorithm.
 	* common.opt (freorder-blocks-algorithm=): New flag.

gcc/doc/invoke.texi

@@ -430,6 +430,7 @@ Objective-C and Objective-C++ Dialects}.
 -fprofile-use -fprofile-use=@var{path} -fprofile-values @gol
 -fprofile-reorder-functions @gol
 -freciprocal-math -free -frename-registers -freorder-blocks @gol
+-freorder-blocks-algorithm=@var{algorithm} @gol
 -freorder-blocks-and-partition -freorder-functions @gol
 -frerun-cse-after-loop -freschedule-modulo-scheduled-loops @gol
 -frounding-math -fsched2-use-superblocks -fsched-pressure @gol
@@ -7689,6 +7690,7 @@ compilation time.
 -fipa-reference @gol
 -fmerge-constants @gol
 -fmove-loop-invariants @gol
+-freorder-blocks @gol
 -fshrink-wrap @gol
 -fsplit-wide-types @gol
 -ftree-bit-ccp @gol
@@ -7745,7 +7747,8 @@ also turns on the following optimization flags:
 -foptimize-strlen @gol
 -fpartial-inlining @gol
 -fpeephole2 @gol
--freorder-blocks -freorder-blocks-and-partition -freorder-functions @gol
+-freorder-blocks-algorithm=stc @gol
+-freorder-blocks-and-partition -freorder-functions @gol
 -frerun-cse-after-loop  @gol
 -fsched-interblock  -fsched-spec @gol
 -fschedule-insns  -fschedule-insns2 @gol
@@ -7782,8 +7785,8 @@ optimizations designed to reduce code size.
 
 @option{-Os} disables the following optimization flags:
 @gccoptlist{-falign-functions  -falign-jumps  -falign-loops @gol
--falign-labels  -freorder-blocks  -freorder-blocks-and-partition @gol
--fprefetch-loop-arrays}
+-falign-labels  -freorder-blocks  -freorder-blocks-algorithm=stc @gol
+-freorder-blocks-and-partition  -fprefetch-loop-arrays}
 
 @item -Ofast
 @opindex Ofast
@@ -9134,7 +9137,19 @@ The default is @option{-fguess-branch-probability} at levels
 Reorder basic blocks in the compiled function in order to reduce number of
 taken branches and improve code locality.
 
-Enabled at levels @option{-O2}, @option{-O3}.
+Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -freorder-blocks-algorithm=@var{algorithm}
+@opindex freorder-blocks-algorithm
+Use the specified algorithm for basic block reordering.  The
+@var{algorithm} argument can be @samp{simple}, which does not increase
+code size (except sometimes due to secondary effects like alignment),
+or @samp{stc}, the ``software trace cache'' algorithm, which tries to
+put all often executed code together, minimizing the number of branches
+executed by making extra copies of code.
+
+The default is @samp{simple} at levels @option{-O}, @option{-Os}, and
+@samp{stc} at levels @option{-O2}, @option{-O3}.
 
 @item -freorder-blocks-and-partition
 @opindex freorder-blocks-and-partition