> Here is an alternative, almost completely untested, patch, which
> uses DW_OP_fbreg <N> for the arguments of dynamically realigned functions.
> draptest.c now works...
I've attached a slightly revamped, IMO easier to understand version. Stack
realignment with DRAP is quite seldom on the mainline (because everything is
ACCUMULATE_OUTGOING_ARGS now) so I don't think this will make any difference
in practice. Tested on i586 and x86-64.
* var-tracking.c (vt_add_function_parameter): Remap incoming MEMs with
crtl->args.internal_arg_pointer based address to arg_pointer_rtx if
there is a DRAP register.
(vt_init_cfa_base): Don't equate cfa_base_rtx if stack was realigned.
(vt_initialize): Initialize cfa_base_rtx if there is a DRAP register.
--
Eric Botcazou
Index: var-tracking.c
===================================================================
--- var-tracking.c (revision 174377)
+++ var-tracking.c (working copy)
@@ -8398,6 +8398,27 @@ vt_add_function_parameter (tree parm)
if (GET_MODE (decl_rtl) == BLKmode || GET_MODE (incoming) == BLKmode)
return;
+ /* If there is a DRAP register, rewrite the incoming location of parameters
+ passed on the stack into MEMs based on the argument pointer, as the DRAP
+ register can be reused for other purposes and we do not track locations
+ based on generic registers. See also vt_initialize. */
+ if (MEM_P (incoming)
+ && stack_realign_drap
+ && cfa_base_rtx
+ && (XEXP (incoming, 0) == crtl->args.internal_arg_pointer
+ || (GET_CODE (XEXP (incoming, 0)) == PLUS
+ && XEXP (XEXP (incoming, 0), 0)
+ == crtl->args.internal_arg_pointer
+ && CONST_INT_P (XEXP (XEXP (incoming, 0), 1)))))
+ {
+ HOST_WIDE_INT off = -FIRST_PARM_OFFSET (current_function_decl);
+ if (GET_CODE (XEXP (incoming, 0)) == PLUS)
+ off += INTVAL (XEXP (XEXP (incoming, 0), 1));
+ incoming
+ = replace_equiv_address_nv (incoming,
+ plus_constant (arg_pointer_rtx, off));
+ }
+
if (!vt_get_decl_and_offset (incoming, &decl, &offset))
{
if (REG_P (incoming) || MEM_P (incoming))
@@ -8647,9 +8668,11 @@ vt_init_cfa_base (void)
/* Tell alias analysis that cfa_base_rtx should share
find_base_term value with stack pointer or hard frame pointer. */
- vt_equate_reg_base_value (cfa_base_rtx,
- frame_pointer_needed
- ? hard_frame_pointer_rtx : stack_pointer_rtx);
+ if (!frame_pointer_needed)
+ vt_equate_reg_base_value (cfa_base_rtx, stack_pointer_rtx);
+ else if (!crtl->stack_realign_tried)
+ vt_equate_reg_base_value (cfa_base_rtx, hard_frame_pointer_rtx);
+
val = cselib_lookup_from_insn (cfa_base_rtx, GET_MODE (cfa_base_rtx), 1,
VOIDmode, get_insns ());
preserve_value (val);
@@ -8780,6 +8803,31 @@ vt_initialize (void)
fp_cfa_offset = -1;
}
+ /* If the stack is realigned and a DRAP register is used, we're going to
+ rewrite MEMs based on it representing incoming locations of parameters
+ passed on the stack into MEMs based on the argument pointer. Although
+ we aren't going to rewrite other MEMs, we need to set up the virtual
+ CFA pointer in order to ensure that the argument pointer will be seen
+ as a constant throughout the function. */
+ else if (stack_realign_drap)
+ {
+ rtx reg, elim;
+
+#ifdef FRAME_POINTER_CFA_OFFSET
+ reg = frame_pointer_rtx;
+#else
+ reg = arg_pointer_rtx;
+#endif
+ elim = eliminate_regs (reg, VOIDmode, NULL_RTX);
+ if (elim != reg)
+ {
+ if (GET_CODE (elim) == PLUS)
+ elim = XEXP (elim, 0);
+ if (elim == hard_frame_pointer_rtx)
+ vt_init_cfa_base ();
+ }
+ }
+
if (frame_pointer_needed)
{
rtx insn;
