Hi Xiong Hu,
On Mon, Nov 25, 2019 at 10:24:35AM +0800, luoxhu wrote:
> P9LE generated instruction is not worse than P8LE.
> mtvsrdd;xxlnot;stxv vs. not;not;std;std.
To be clear: it can have longer latency, but latency via memory is not
so critical, and this does save decode and other resources. It's hard
to choose which is best :-)
> * gcc.target/powerpc/pr72804.c: Split the store function to...
> * gcc.target/powerpc/pr92398.h: ... this one. New.
I wanted to say that splitting one single function to a header file is a
bit overkill, but it gives a nice place to discuss the differences in
generated code on different CPUs, so okay, it's useful :-)
> + store generates difference instructions as below:
> + P9+: mtvsrdd;xxlnot;stxv.
> + P8/P7/P6 LE: not;not;std;std.
> + P8 BE: mtvsrd;mtvsrd;xxpermdi;xxlnor;stxvd2x.
> + P7/P6 BE: std;std;addi;lxvd2x;xxlnor;stxvd2x.
> + P9+ and P9- LE are expected, P6/P7/P8 BE are unexpected. */
Great overview, thanks.
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr92398.p9+.c
> b/gcc/testsuite/gcc.target/powerpc/pr92398.p9+.c
> new file mode 100644
> index 00000000000..2ebe2025cef
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr92398.p9+.c
> @@ -0,0 +1,10 @@
> +/* { dg-do compile { target { lp64 && p9+ } } } */
> +/* { dg-require-effective-target powerpc_vsx_ok } */
> +/* { dg-options "-O2 -mvsx" } */
> +
> +/* { dg-final { scan-assembler-times {\mmtvsrdd\M} 1 } } */
> +/* { dg-final { scan-assembler-times {\mxxlnor\M} 1 } } */
> +/* { dg-final { scan-assembler-times {\mstxv\M} 1 } } */
Maybe add scan-assembler-not for "not" and "std", and in the < p9 testcase
for these three?
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr92398.p9-.c
> @@ -0,0 +1,10 @@
> +/* { dg-do compile { target { lp64 && {! p9+} } } } */
> +/* { dg-require-effective-target powerpc_vsx_ok } */
> +/* { dg-options "-O2 -mvsx" } */
> +
> +/* { dg-final { scan-assembler-times {\mnot\M} 2 { xfail be } } } */
> +/* { dg-final { scan-assembler-times {\mstd\M} 2 { xfail { {p8} && {be} } }
> } } */
I think you can write that as just
/* { dg-final { scan-assembler-times {\mstd\M} 2 { xfail { p8 && be } } } } */
Okay for trunk with or without such tweaks. Thanks, and sorry the review
took a while!
Segher
