On Sat, Jun 3, 2023 at 3:52 PM Takayuki 'January June' Suwa
<jjsuwa_sys3...@yahoo.co.jp> wrote:
>
> This patch optimizes both the boolean evaluation of and the branching of
> EQ/NE against INT_MIN (-2147483648), by taking advantage of the specifi-
> cation the ABS machine instruction on Xtensa returns INT_MIN iff INT_MIN,
> otherwise non-negative value.
>
> /* example */
> int test0(int x) {
> return (x == -2147483648);
> }
> int test1(int x) {
> return (x != -2147483648);
> }
> extern void foo(void);
> void test2(int x) {
> if(x == -2147483648)
> foo();
> }
> void test3(int x) {
> if(x != -2147483648)
> foo();
> }
>
> ;; before
> test0:
> movi.n a9, -1
> slli a9, a9, 31
> add.n a2, a2, a9
> nsau a2, a2
> srli a2, a2, 5
> ret.n
> test1:
> movi.n a9, -1
> slli a9, a9, 31
> add.n a9, a2, a9
> movi.n a2, 1
> moveqz a2, a9, a9
> ret.n
> test2:
> movi.n a9, -1
> slli a9, a9, 31
> bne a2, a9, .L3
> j.l foo, a9
> .L3:
> ret.n
> test3:
> movi.n a9, -1
> slli a9, a9, 31
> beq a2, a9, .L5
> j.l foo, a9
> .L5:
> ret.n
>
> ;; after
> test0:
> abs a2, a2
> extui a2, a2, 31, 1
> ret.n
> test1:
> abs a2, a2
> srai a2, a2, 31
> addi.n a2, a2, 1
> ret.n
> test2:
> abs a2, a2
> bbci a2, 31, .L3
> j.l foo, a9
> .L3:
> ret.n
> test3:
> abs a2, a2
> bbsi a2, 31, .L5
> j.l foo, a9
> .L5:
> ret.n
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa.md (*btrue_INT_MIN, *eqne_INT_MIN):
> New insn_and_split patterns.
> ---
> gcc/config/xtensa/xtensa.md | 64 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.
--
Thanks.
-- Max
