On Thu, 2023-11-16 at 20:30 +0800, Li Wei wrote:
> The LoongArch has defined ctz and clz on the backend, but if we want GCC
> do CTZ transformation optimization in forwprop2 pass, GCC need to know
> the value of c[lt]z at zero, which may be beneficial for some test cases
> (like spec2017 deepsjeng_r).
>
> After implementing the macro, we test dynamic instruction count on
> deepsjeng_r:
> - before 1688423249186
> - after 1660311215745 (1.66% reduction)
LGTM, nice catch!
> ---
> gcc/config/loongarch/loongarch.h | 5 +++++
> gcc/testsuite/gcc.dg/pr90838.c | 5 +++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/gcc/config/loongarch/loongarch.h
> b/gcc/config/loongarch/loongarch.h
> index ddac8e98ea9..115222e70fd 100644
> --- a/gcc/config/loongarch/loongarch.h
> +++ b/gcc/config/loongarch/loongarch.h
> @@ -1239,3 +1239,8 @@ struct GTY (()) machine_function
>
> #define TARGET_EXPLICIT_RELOCS \
> (la_opt_explicit_relocs == EXPLICIT_RELOCS_ALWAYS)
> +
> +#define CLZ_DEFINED_VALUE_AT_ZERO(MODE, VALUE) \
> + ((VALUE) = GET_MODE_UNIT_BITSIZE (MODE), 2)
> +#define CTZ_DEFINED_VALUE_AT_ZERO(MODE, VALUE) \
> + ((VALUE) = GET_MODE_UNIT_BITSIZE (MODE), 2)
> diff --git a/gcc/testsuite/gcc.dg/pr90838.c b/gcc/testsuite/gcc.dg/pr90838.c
> index 759059683a9..40aad70499d 100644
> --- a/gcc/testsuite/gcc.dg/pr90838.c
> +++ b/gcc/testsuite/gcc.dg/pr90838.c
> @@ -83,3 +83,8 @@ int ctz4 (unsigned long x)
> /* { dg-final { scan-assembler-times "ctz\t" 3 { target { rv32 } } } } */
> /* { dg-final { scan-assembler-times "andi\t" 1 { target { rv32 } } } } */
> /* { dg-final { scan-assembler-times "mul\t" 1 { target { rv32 } } } } */
> +
> +/* { dg-final { scan-tree-dump-times {= \.CTZ} 4 "forwprop2" { target {
> loongarch64*-*-* } } } } */
> +/* { dg-final { scan-assembler-times "ctz.d\t" 1 { target { loongarch64*-*-*
> } } } } */
> +/* { dg-final { scan-assembler-times "ctz.w\t" 3 { target { loongarch64*-*-*
> } } } } */
> +/* { dg-final { scan-assembler-times "andi\t" 4 { target { loongarch64*-*-*
> } } } } */
--
Xi Ruoyao <xry...@xry111.site>
School of Aerospace Science and Technology, Xidian University
