invoke.texi (-fconserve-stack): Document.

* invoke.texi (-fconserve-stack): Document.
	* opts.c (decode_options): Handle conserve_stack.
	* common.opt (fconvserve_stack): New.

From-SVN: r140362

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2008-09-14  Jan Hubicka  <jh@suse.cz>
+
+	* invoke.texi (-fconserve-stack): Document.
+	* opts.c (decode_options): Handle conserve_stack.
+	* common.opt (fconvserve_stack): New.
+
 2008-09-14  David Edelsohn  <edelsohn@gnu.org>
 
 	* config.host: Add x-aix to host_xmake_file.

gcc/common.opt

@@ -385,6 +385,10 @@ fcommon
 Common Report Var(flag_no_common,0) Optimization
 Do not put uninitialized globals in the common section
 
+fconserve-stack
+Common Var(flag_conserve_stack,0) Optimization
+Do not perform optimizations increasing noticeably stack usage
+
 fcprop-registers
 Common Report Var(flag_cprop_registers) Optimization
 Perform a register copy-propagation optimization pass

gcc/doc/invoke.texi

@@ -323,8 +323,8 @@ Objective-C and Objective-C++ Dialects}.
 -falign-labels[=@var{n}] -falign-loops[=@var{n}] -fassociative-math @gol
 -fauto-inc-dec -fbranch-probabilities -fbranch-target-load-optimize @gol
 -fbranch-target-load-optimize2 -fbtr-bb-exclusive -fcaller-saves @gol
--fcheck-data-deps -fcprop-registers -fcrossjumping -fcse-follow-jumps @gol
--fcse-skip-blocks -fcx-fortran-rules -fcx-limited-range @gol
+-fcheck-data-deps -fconserve-stack -fcprop-registers -fcrossjumping @gol
+-fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules -fcx-limited-range @gol
 -fdata-sections -fdce -fdce @gol
 -fdelayed-branch -fdelete-null-pointer-checks -fdse -fdse @gol
 -fearly-inlining -fexpensive-optimizations -ffast-math @gol
@@ -5871,6 +5871,13 @@ those which have no call-preserved registers to use instead.
 
 Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
 
+@item -fconserve-stack
+@opindex fconserve-stack
+Attempt to minimize stack usage.  The compiler will attempt to use less
+stack space, even if that makes the program slower.  This option
+implies setting the @option{large-stack-frame} parameter to 100
+and the @option{large-stack-frame-growth} parameter to 400.
+
 @item -ftree-reassoc
 @opindex ftree-reassoc
 Perform reassociation on trees.  This flag is enabled by default

gcc/opts.c

@@ -1112,6 +1112,14 @@ decode_options (unsigned int argc, const char **argv)
       optimization_current_node = optimization_default_node;
       first_time_p = false;
     }
+  if (flag_conserve_stack)
+    {
+      if (!PARAM_SET_P (PARAM_LARGE_STACK_FRAME))
+        PARAM_VALUE (PARAM_LARGE_STACK_FRAME) = 100;
+      if (!PARAM_SET_P (PARAM_STACK_FRAME_GROWTH))
+        PARAM_VALUE (PARAM_STACK_FRAME_GROWTH) = 40;
+    }
+
 }
 
 #define LEFT_COLUMN	27