Re: [PATCH V1] HIGH part of symbol ref is invalid for constant pool

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi Jeff,

on 2022/7/19 22:30, Jiufu Guo wrote:
> Hi,
> 
> In patch https://gcc.gnu.org/pipermail/gcc-patches/2022-July/597712.html,
> test case was not added.  After more check, a testcase is added for it.
> 

Good to see that you constructed one actual test case, nice!  :)

> The high part of the symbol address is invalid for the constant pool.
> In function rs6000_cannot_force_const_mem, we already return true for
> "HIGH with UNSPEC" rtx.  Below are some examples also indicate the high
> part of a symbol_ref:
> (high:DI (const:DI (plus:DI (symbol_ref:DI ("xx") (const_int 12 [0xc])))))
> (high:DI (symbol_ref:DI ("var_1")..)))
> 
> This patch updates rs6000_cannot_force_const_mem to return true for
> rtx with HIGH code.
> 
> Bootstrapped and regtested on ppc64le and ppc64.
> Is it ok for trunk?

I think this patch is OK with some nits below tweaked.

> 
> BR,
> Jeff(Jiufu)
> 
> 
> gcc/ChangeLog:
> 
> 	* config/rs6000/rs6000.cc (rs6000_cannot_force_const_mem):
> 	Return true for HIGH code rtx.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.target/powerpc/constpoolcheck.c: New test.
> 
> ---
>  gcc/config/rs6000/rs6000.cc                       |  7 +++++--
>  gcc/testsuite/gcc.target/powerpc/constpoolcheck.c | 11 +++++++++++
>  2 files changed, 16 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/powerpc/constpoolcheck.c
> 
> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
> index 0af2085adc0..d56832ebbfc 100644
> --- a/gcc/config/rs6000/rs6000.cc
> +++ b/gcc/config/rs6000/rs6000.cc
> @@ -9704,8 +9704,11 @@ rs6000_init_stack_protect_guard (void)
>  static bool
>  rs6000_cannot_force_const_mem (machine_mode mode ATTRIBUTE_UNUSED, rtx x)
>  {
> -  if (GET_CODE (x) == HIGH
> -      && GET_CODE (XEXP (x, 0)) == UNSPEC)
> +  /* High part of a symbol ref/address can not be put into constant pool. e.g.

Nit: two spaces after the period in "... pool.".

> +     (high:DI (symbol_ref:DI ("var")..)) or

Nit: You have one "or" at the end of the above line, I think it's better to
keep the below line consistent by either removing the above " or" or adding
one "or" at the end of the below line.

> +     (high:DI (unspec:DI [(symbol_ref/u:DI ("*.LC0")..)


> +     (high:DI (const:DI (plus:DI (symbol_ref:DI ("xx")) (const_int 12)))).  */
> +  if (GET_CODE (x) == HIGH)
>      return true;
> 
>    /* A TLS symbol in the TOC cannot contain a sum.  */
> diff --git a/gcc/testsuite/gcc.target/powerpc/constpoolcheck.c b/gcc/testsuite/gcc.target/powerpc/constpoolcheck.c
> new file mode 100644
> index 00000000000..ed7a994827b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/constpoolcheck.c

Maybe it's good to name it to "const-pool-check.c" or "not-force-const-mem.c".

> @@ -0,0 +1,11 @@
> +/* { dg-do compile { target powerpc*-*-* } } */

Nit: this "dg-do" line isn't needed since all here are default.

BR,
Kewen

> +/* { dg-options "-O1 -mdejagnu-cpu=power10" } */
> +/* (high:DI (symbol_ref:DI ("var_48")..))) should not cause ICE. */
> +extern short var_48;
> +void
> +foo (double *r)
> +{
> +  if (var_48)
> +    *r = 1234.5678;
> +}
> +