calls.c (prepare_call_address): Transform PLT call to GOT lookup and indirect…

calls.c (prepare_call_address): Transform PLT call to GOT lookup and indirect call by forcing address into a...

	* 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.
	* doc/invoke.texi (Code Generation Options): Add -fno-plt.
	([-fno-plt]): Document.

From-SVN: r223003

gcc/ChangeLog

+2015-05-11  Alexander Monakov  <amonakov@ispras.ru>
+
+	* 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.
+	* doc/invoke.texi (Code Generation Options): Add -fno-plt.
+	([-fno-plt]): Document.
+
 2015-05-11  Markus Trippelsdorf  <markus@trippelsdorf.de>
 	
 	PR bootstrap/66105

gcc/calls.c

@@ -225,6 +225,12 @@ prepare_call_address (tree fndecl_or_type, rtx funexp, rtx static_chain_value,
 	       && 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)
     {
       if (!NO_FUNCTION_CSE && optimize && ! flag_no_function_cse)

gcc/common.opt

@@ -1781,6 +1781,10 @@ 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) Optimization
+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

gcc/doc/invoke.texi

@@ -1128,7 +1128,7 @@ See S/390 and zSeries Options.
 -finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{} @gol
 -finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{} @gol
 -fno-common  -fno-ident @gol
--fpcc-struct-return  -fpic  -fPIC -fpie -fPIE @gol
+-fpcc-struct-return  -fpic  -fPIC -fpie -fPIE -fno-plt @gol
 -fno-jump-tables @gol
 -frecord-gcc-switches @gol
 -freg-struct-return  -fshort-enums @gol
@@ -23782,6 +23782,16 @@ used during linking.
 @code{__pie__} and @code{__PIE__}.  The macros have the value 1
 for @option{-fpie} and 2 for @option{-fPIE}.
 
+@item -fno-plt
+@opindex fno-plt
+Do not use PLT for external function calls in position-independent code.
+Instead, load callee address at call site from GOT and branch to it.
+This leads to more efficient code by eliminating PLT stubs and exposing
+GOT load to optimizations.  On architectures such as 32-bit x86 where
+PLT stubs expect GOT pointer in a specific register, this gives more
+register allocation freedom to the compiler.  Lazy binding requires PLT:
+with @option{-fno-plt} all external symbols are resolved at load time.
+
 @item -fno-jump-tables
 @opindex fno-jump-tables
 Do not use jump tables for switch statements even where it would be