[Patch] Add option ftree-stdarg-opt

[Tom de Vries <Tom_deVries at mentor dot com>]

Hi,

this patch adds option ftree-stdarg-opt, which switches pass_stdarg on or off.

Pass_stdarg does an optimization on cfun->va_list_gpr/fpr_size, and since it's 
an optimization, it's useful to be able to switch it off in case of a problem 
with the pass.

This is not a regression or documentation fix, so it doesn't classify as a stage 
4 patch. I could imagine it still being included in stage4 because it adds the 
possibility for a workaround in case of problems.

Bootstrapped and reg-tested on x86_64.

OK for stage1 (or even stage 4)?

Thanks,
- Tom

2015-02-17  Tom de Vries  <tom@codesourcery.com>

	* common.opt (ftree-stdarg-opt): New option.
	* tree-stdarg.c (pass_stdarg::gate): Use flag_tree_stdarg_opt.
---
 gcc/common.opt    | 4 ++++
 gcc/tree-stdarg.c | 5 +++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/gcc/common.opt b/gcc/common.opt
index 0c60e84..ed14b40 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2065,6 +2065,10 @@ fssa-phiopt
 Common Report Var(flag_ssa_phiopt) Optimization
 Optimize conditional patterns using SSA PHI nodes
 
+ftree-stdarg-opt
+Common Report Var(flag_tree_stdarg_opt) Init(1) Optimization
+Optimize amount of stdarg registers saved to stack at start of function
+
 fvariable-expansion-in-unroller
 Common Report Var(flag_variable_expansion_in_unroller) Optimization
 Apply variable expansion when loops are unrolled
diff --git a/gcc/tree-stdarg.c b/gcc/tree-stdarg.c
index 2cf0ca3..975ff97 100644
--- a/gcc/tree-stdarg.c
+++ b/gcc/tree-stdarg.c
@@ -704,8 +704,9 @@ public:
   /* opt_pass methods: */
   virtual bool gate (function *fun)
     {
-      /* This optimization is only for stdarg functions.  */
-      return fun->stdarg != 0;
+      return (flag_tree_stdarg_opt
+	      /* This optimization is only for stdarg functions.  */
+	      && fun->stdarg != 0);
     }
 
   virtual unsigned int execute (function *);
-- 
1.9.1