[2/3] xtensa: Add 'subtraction from constant' insn pattern
Commit Message
This patch makes try to eliminate using temporary pseudo for
'(minus:SI (const_int) (reg:SI))' if the addition of negative constant
value can be emitted in a single machine instruction.
/* example */
int test0(int x) {
return 1 - x;
}
int test1(int x) {
return 100 - x;
}
int test2(int x) {
return 25600 - x;
}
;; before
test0:
movi.n a9, 1
sub a2, a9, a2
ret.n
test1:
movi a9, 0x64
sub a2, a9, a2
ret.n
test2:
movi.n a9, 0x19
slli a9, a9, 10
sub a2, a9, a2
ret.n
;; after
test0:
addi.n a2, a2, -1
neg a2, a2
ret.n
test1:
addi a2, a2, -100
neg a2, a2
ret.n
test2:
addmi a2, a2, -0x6400
neg a2, a2
ret.n
gcc/ChangeLog:
* config/xtensa/xtensa-protos.h (xtensa_m1_or_1_thru_15):
New prototype.
* config/xtensa/xtensa.cc (xtensa_m1_or_1_thru_15):
New function.
* config/xtensa/constraints.md (O):
Change to use the above function.
* config/xtensa/xtensa.md (*subsi3_from_const):
New insn_and_split pattern.
---
gcc/config/xtensa/constraints.md | 2 +-
gcc/config/xtensa/xtensa-protos.h | 1 +
gcc/config/xtensa/xtensa.cc | 7 +++++++
gcc/config/xtensa/xtensa.md | 24 ++++++++++++++++++++++++
4 files changed, 33 insertions(+), 1 deletion(-)
Comments
On Thu, May 25, 2023 at 8:13 AM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> This patch makes try to eliminate using temporary pseudo for
> '(minus:SI (const_int) (reg:SI))' if the addition of negative constant
> value can be emitted in a single machine instruction.
>
> /* example */
> int test0(int x) {
> return 1 - x;
> }
> int test1(int x) {
> return 100 - x;
> }
> int test2(int x) {
> return 25600 - x;
> }
>
> ;; before
> test0:
> movi.n a9, 1
> sub a2, a9, a2
> ret.n
> test1:
> movi a9, 0x64
> sub a2, a9, a2
> ret.n
> test2:
> movi.n a9, 0x19
> slli a9, a9, 10
> sub a2, a9, a2
> ret.n
>
> ;; after
> test0:
> addi.n a2, a2, -1
> neg a2, a2
> ret.n
> test1:
> addi a2, a2, -100
> neg a2, a2
> ret.n
> test2:
> addmi a2, a2, -0x6400
> neg a2, a2
> ret.n
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa-protos.h (xtensa_m1_or_1_thru_15):
> New prototype.
> * config/xtensa/xtensa.cc (xtensa_m1_or_1_thru_15):
> New function.
> * config/xtensa/constraints.md (O):
> Change to use the above function.
> * config/xtensa/xtensa.md (*subsi3_from_const):
> New insn_and_split pattern.
> ---
> gcc/config/xtensa/constraints.md | 2 +-
> gcc/config/xtensa/xtensa-protos.h | 1 +
> gcc/config/xtensa/xtensa.cc | 7 +++++++
> gcc/config/xtensa/xtensa.md | 24 ++++++++++++++++++++++++
> 4 files changed, 33 insertions(+), 1 deletion(-)
Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.
@@ -108,7 +108,7 @@
(define_constraint "O"
"An integer constant that can be used in ADDI.N instructions."
(and (match_code "const_int")
- (match_test "ival == -1 || IN_RANGE (ival, 1, 15)")))
+ (match_test "xtensa_m1_or_1_thru_15 (ival)")))
(define_constraint "P"
"An integer constant that can be used as a mask value in an EXTUI
@@ -27,6 +27,7 @@ extern bool xtensa_simm8x256 (HOST_WIDE_INT);
extern bool xtensa_simm12b (HOST_WIDE_INT);
extern bool xtensa_b4const_or_zero (HOST_WIDE_INT);
extern bool xtensa_b4constu (HOST_WIDE_INT);
+extern bool xtensa_m1_or_1_thru_15 (HOST_WIDE_INT);
extern bool xtensa_mask_immediate (HOST_WIDE_INT);
extern bool xtensa_mem_offset (unsigned, machine_mode);
@@ -471,6 +471,13 @@ xtensa_b4constu (HOST_WIDE_INT v)
}
+bool
+xtensa_m1_or_1_thru_15 (HOST_WIDE_INT v)
+{
+ return v == -1 || IN_RANGE (v, 1, 15);
+}
+
+
bool
xtensa_mask_immediate (HOST_WIDE_INT v)
{
@@ -216,6 +216,30 @@
(set_attr "mode" "SI")
(set_attr "length" "3")])
+(define_insn_and_split "*subsi3_from_const"
+ [(set (match_operand:SI 0 "register_operand" "=a")
+ (minus:SI (match_operand:SI 1 "const_int_operand" "i")
+ (match_operand:SI 2 "register_operand" "r")))]
+ "xtensa_simm8 (-INTVAL (operands[1]))
+ || xtensa_simm8x256 (-INTVAL (operands[1]))"
+ "#"
+ "&& 1"
+ [(set (match_dup 0)
+ (plus:SI (match_dup 2)
+ (match_dup 1)))
+ (set (match_dup 0)
+ (neg:SI (match_dup 0)))]
+{
+ operands[1] = GEN_INT (-INTVAL (operands[1]));
+}
+ [(set_attr "type" "arith")
+ (set_attr "mode" "SI")
+ (set (attr "length")
+ (if_then_else (match_test "TARGET_DENSITY
+ && xtensa_m1_or_1_thru_15 (-INTVAL (operands[1]))")
+ (const_int 5)
+ (const_int 6)))])
+
(define_insn "subsf3"
[(set (match_operand:SF 0 "register_operand" "=f")
(minus:SF (match_operand:SF 1 "register_operand" "f")