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
