This patch enforces the use of "addmi" machine instruction instead of
addition/subtraction with two source registers for adjusting the stack
pointer, if the adjustment fits into a signed 16-bit and is also a multiple
of 256.
/* example */
void test(void) {
char buffer[4096];
__asm__(""::"m"(buffer));
}
;; before
test:
movi.n a9, 1
slli a9, a9, 12
sub sp, sp, a9
movi.n a9, 1
slli a9, a9, 12
add.n sp, sp, a9
addi sp, sp, 0
ret.n
;; after
test:
addmi sp, sp, -0x1000
addmi sp, sp, 0x1000
ret.n
gcc/ChangeLog:
* config/xtensa/xtensa.cc (xtensa_expand_prologue):
Use an "addmi" machine instruction for updating the stack pointer
rather than addition/subtraction via hard register A9, if the amount
of change satisfies the literal value conditions of that instruction
when the CALL0 ABI is used.
(xtensa_expand_epilogue): Ditto.
And also inhibit the stack pointer addition of constant zero.
---
gcc/config/xtensa/xtensa.cc | 79 +++++++++++++++++++++++++------------
1 file changed, 54 insertions(+), 25 deletions(-)
diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index 6ac879c38fb..b673b6764da 100644
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -3150,7 +3150,6 @@ xtensa_expand_prologue (void)
rtx_insn *insn = NULL;
rtx note_rtx;
-
total_size = compute_frame_size (get_frame_size ());
if (flag_stack_usage_info)
@@ -3206,10 +3205,17 @@ xtensa_expand_prologue (void)
}
else
{
- rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
- emit_move_insn (tmp_reg, GEN_INT (total_size));
- insn = emit_insn (gen_subsi3 (stack_pointer_rtx,
- stack_pointer_rtx, tmp_reg));
+ if (xtensa_simm8x256 (-total_size))
+ insn = emit_insn (gen_addsi3 (stack_pointer_rtx,
+ stack_pointer_rtx,
+ GEN_INT (-total_size)));
+ else
+ {
+ rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
+ emit_move_insn (tmp_reg, GEN_INT (total_size));
+ insn = emit_insn (gen_subsi3 (stack_pointer_rtx,
+ stack_pointer_rtx, tmp_reg));
+ }
RTX_FRAME_RELATED_P (insn) = 1;
note_rtx = gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
@@ -3237,11 +3243,19 @@ xtensa_expand_prologue (void)
if (total_size > 1024
|| (!callee_save_size && total_size > 128))
{
- rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
- emit_move_insn (tmp_reg, GEN_INT (total_size -
- callee_save_size));
- insn = emit_insn (gen_subsi3 (stack_pointer_rtx,
- stack_pointer_rtx, tmp_reg));
+ if (xtensa_simm8x256 (callee_save_size - total_size))
+ insn = emit_insn (gen_addsi3 (stack_pointer_rtx,
+ stack_pointer_rtx,
+ GEN_INT (callee_save_size -
+ total_size)));
+ else
+ {
+ rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
+ emit_move_insn (tmp_reg, GEN_INT (total_size -
+ callee_save_size));
+ insn = emit_insn (gen_subsi3 (stack_pointer_rtx,
+ stack_pointer_rtx, tmp_reg));
+ }
RTX_FRAME_RELATED_P (insn) = 1;
note_rtx = gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
@@ -3315,12 +3329,21 @@ xtensa_expand_epilogue (bool sibcall_p)
if (cfun->machine->current_frame_size > (frame_pointer_needed ? 127 :
1024))
{
- rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
- emit_move_insn (tmp_reg, GEN_INT (cfun->machine->current_frame_size -
- cfun->machine->callee_save_size));
- emit_insn (gen_addsi3 (stack_pointer_rtx, frame_pointer_needed ?
- hard_frame_pointer_rtx : stack_pointer_rtx,
- tmp_reg));
+ if (xtensa_simm8x256 (cfun->machine->current_frame_size -
+ cfun->machine->callee_save_size))
+ emit_insn (gen_addsi3 (stack_pointer_rtx, frame_pointer_needed ?
+ hard_frame_pointer_rtx : stack_pointer_rtx,
+ GEN_INT (cfun->machine->current_frame_size -
+ cfun->machine->callee_save_size)));
+ else
+ {
+ rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
+ emit_move_insn (tmp_reg, GEN_INT
(cfun->machine->current_frame_size -
+
cfun->machine->callee_save_size));
+ emit_insn (gen_addsi3 (stack_pointer_rtx, frame_pointer_needed ?
+ hard_frame_pointer_rtx : stack_pointer_rtx,
+ tmp_reg));
+ }
offset = cfun->machine->callee_save_size - UNITS_PER_WORD;
}
else
@@ -3360,18 +3383,24 @@ xtensa_expand_epilogue (bool sibcall_p)
offset = cfun->machine->current_frame_size;
else
offset = cfun->machine->callee_save_size;
-
- emit_insn (gen_addsi3 (stack_pointer_rtx,
- stack_pointer_rtx,
- GEN_INT (offset)));
+ if (offset)
+ emit_insn (gen_addsi3 (stack_pointer_rtx,
+ stack_pointer_rtx,
+ GEN_INT (offset)));
}
else
{
- rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
- emit_move_insn (tmp_reg,
- GEN_INT (cfun->machine->current_frame_size));
- emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx,
- tmp_reg));
+ if (xtensa_simm8x256 (cfun->machine->current_frame_size))
+ emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx,
+ GEN_INT
(cfun->machine->current_frame_size)));
+ else
+ {
+ rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
+ emit_move_insn (tmp_reg,
+ GEN_INT (cfun->machine->current_frame_size));
+ emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx,
+ tmp_reg));
+ }
}
}
--
2.20.1
