Hi,
This patch checks an assignment to see if the "from" is about parameter,
and if the parameter may passing through registers, then use the register
mode to move sub-blocks for the assignment.
Bootstraped and regtested on ppc{,le} and x86_64.
Is this ok for trunk?
BR,
Jeff (Jiufu)
gcc/ChangeLog:
* expr.cc (move_sub_blocks): New function.
(expand_assignment): Call move_sub_blocks for assigning from parameter.
---
gcc/expr.cc | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
diff --git a/gcc/expr.cc b/gcc/expr.cc
index d9407432ea5..201fee6fd9a 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -5559,6 +5559,57 @@ mem_ref_refers_to_non_mem_p (tree ref)
return non_mem_decl_p (base);
}
+/* Sub routine of expand_assignment, invoked when assigning from a
+ parameter or assigning to a return val on struct type which may
+ be passed through registers. The mode of register is used to
+ move the content for the assignment.
+
+ This routine generates code for expression FROM which is BLKmode,
+ and move the generated content to TO_RTX by su-blocks in SUB_MODE. */
+
+static void
+move_sub_blocks (rtx to_rtx, tree from, machine_mode sub_mode, bool
nontemporal)
+{
+ HOST_WIDE_INT size, sub_size;
+ int len;
+
+ gcc_assert (MEM_P (to_rtx));
+
+ size = MEM_SIZE (to_rtx).to_constant ();
+ sub_size = GET_MODE_SIZE (sub_mode).to_constant ();
+ len = size / sub_size;
+
+ /* As there are limit registers for passing parameters or return
+ value according target ABI. It would be not profitable to move
+ through sub-modes, if the size does not follow registers. */
+ int heurisitic_num = 8;
+ if (!size || (size % sub_size) != 0 || len < 2 || len > heurisitic_num)
+ {
+ push_temp_slots ();
+ rtx result = store_expr (from, to_rtx, 0, nontemporal, false);
+ preserve_temp_slots (result);
+ pop_temp_slots ();
+ return;
+ }
+
+ push_temp_slots ();
+
+ rtx from_rtx;
+ from_rtx = expand_expr (from, NULL_RTX, GET_MODE (to_rtx), EXPAND_NORMAL);
+ for (int i = 0; i < len; i++)
+ {
+ rtx temp = gen_reg_rtx (sub_mode);
+ rtx src = adjust_address (from_rtx, sub_mode, sub_size * i);
+ rtx dest = adjust_address (to_rtx, sub_mode, sub_size * i);
+ emit_move_insn (temp, src);
+ emit_move_insn (dest, temp);
+ }
+
+ preserve_temp_slots (to_rtx);
+ pop_temp_slots ();
+ return;
+}
+
/* Expand an assignment that stores the value of FROM into TO. If NONTEMPORAL
is true, try generating a nontemporal store. */
@@ -6045,6 +6096,25 @@ expand_assignment (tree to, tree from, bool nontemporal)
return;
}
+ /* If it is assigning from a struct param which may be passed via registers,
+ It would be better to use the register's mode to move sub-blocks for the
+ assignment. */
+ if (TREE_CODE (from) == PARM_DECL && mode == BLKmode
+ && DECL_INCOMING_RTL (from)
+ && (GET_CODE (DECL_INCOMING_RTL (from)) == PARALLEL
+ || REG_P (DECL_INCOMING_RTL (from))))
+ {
+ rtx parm = DECL_INCOMING_RTL (from);
+ machine_mode sub_mode;
+ if (REG_P (parm))
+ sub_mode = word_mode;
+ else
+ sub_mode = GET_MODE (XEXP (XVECEXP (parm, 0, 0), 0));
+
+ move_sub_blocks (to_rtx, from, sub_mode, nontemporal);
+ return;
+ }
+
/* Compute FROM and store the value in the rtx we got. */
push_temp_slots ();
--
2.17.1
