[PATCH] Expand PIC calls without PLT with -fno-plt

[Alexander Monakov <amonakov@ispras.ru>]

This patch introduces option -fno-plt that allows to expand calls that would
go via PLT to load the address of the function immediately at call site (which
introduces a GOT load).  Cover letter explains the motivation for this patch.

New option documentation for invoke.texi is missing from the patch; if this is
accepted I'll be happy to send a v2 with documentation added.

	* calls.c (prepare_call_address): Transform PLT call to GOT lookup and
	indirect call by forcing address into a pseudo with -fno-plt.
	* common.opt (flag_plt): New option.

diff --git a/gcc/calls.c b/gcc/calls.c
index 970415d..0c3b9aa 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -222,12 +222,18 @@ prepare_call_address (tree fndecl_or_type, rtx funexp, rtx static_chain_value,
     /* If we are using registers for parameters, force the
        function address into a register now.  */
     funexp = ((reg_parm_seen
 	       && targetm.small_register_classes_for_mode_p (FUNCTION_MODE))
 	      ? force_not_mem (memory_address (FUNCTION_MODE, funexp))
 	      : memory_address (FUNCTION_MODE, funexp));
+  else if (flag_pic && !flag_plt && fndecl_or_type
+	   && TREE_CODE (fndecl_or_type) == FUNCTION_DECL
+	   && !targetm.binds_local_p (fndecl_or_type))
+    {
+      funexp = force_reg (Pmode, funexp);
+    }
   else if (! sibcallp)
     {
 #ifndef NO_FUNCTION_CSE
       if (optimize && ! flag_no_function_cse)
 	funexp = force_reg (Pmode, funexp);
 #endif
diff --git a/gcc/common.opt b/gcc/common.opt
index b49ac46..cd8b256 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1773,12 +1773,16 @@ Common Report Var(flag_pic,1) Negative(fpie)
 Generate position-independent code if possible (small mode)
 
 fpie
 Common Report Var(flag_pie,1) Negative(fPIC)
 Generate position-independent code for executables if possible (small mode)
 
+fplt
+Common Report Var(flag_plt) Init(1)
+Use PLT for PIC calls (-fno-plt: load the address from GOT at call site)
+
 fplugin=
 Common Joined RejectNegative Var(common_deferred_options) Defer
 Specify a plugin to load
 
 fplugin-arg-
 Common Joined RejectNegative Var(common_deferred_options) Defer