On Fri, Jul 15, 2022 at 4:17 PM Takayuki 'January June' Suwa
<jjsuwa_sys3...@yahoo.co.jp> wrote:
>
> This patch enhances the effectiveness of the previously posted one:
> "xtensa: Optimize bitwise AND operation with some specific forms of
> constants".
>
> /* example */
> extern void foo(int);
> void test(int a) {
> if ((a & (-1U << 8)) == (128 << 8)) /* 0 or one of "b4const" */
> foo(a);
> }
>
> ;; before
> .global test
> test:
> movi a3, -0x100
> movi.n a4, 1
> and a3, a2, a3
> slli a4, a4, 15
> bne a3, a4, .L3
> j.l foo, a9
> .L1:
> ret.n
>
> ;; after
> .global test
> test:
> srli a3, a2, 8
> bnei a3, 128, .L1
> j.l foo, a9
> .L1:
> ret.n
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa.md
> (*masktrue_const_pow2_minus_one, *masktrue_const_negative_pow2,
> *masktrue_const_shifted_mask): If the immediate for bitwise AND is
> represented as '-(1 << N)', decrease the lower bound of N from 12
> to 1. And the other immediate for conditional branch is now no
> longer limited to zero, but also one of some positive integers.
> Finally, remove the checks of some conditions, because the comparison
> expressions that don't satisfy such checks are determined as
> compile-time constants and thus will be optimized away before
> RTL expansion.
> ---
> gcc/config/xtensa/xtensa.md | 73 ++++++++++++++++++++++---------------
> 1 file changed, 44 insertions(+), 29 deletions(-)
Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.
--
Thanks.
-- Max
