On Fri, Jun 2, 2023 at 9:36 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> The problem here is DSE was not taking into account the address space
> which meant if you had two addresses say `fs:0` and `gs:0` (on x86_64),
> DSE would think they were the same and remove the first store.
> This fixes that issue by adding a check for the address space too.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
OK.
> PR rtl-optimization/102733
>
> gcc/ChangeLog:
>
> * dse.cc (store_info): Add addrspace field.
> (record_store): Record the address space
> and check to make sure they are the same.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/i386/addr-space-6.c: New test.
> ---
> gcc/dse.cc | 9 ++++++++-
> gcc/testsuite/gcc.target/i386/addr-space-6.c | 21 ++++++++++++++++++++
> 2 files changed, 29 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/addr-space-6.c
>
> diff --git a/gcc/dse.cc b/gcc/dse.cc
> index 802b949cfb2..8b07be17674 100644
> --- a/gcc/dse.cc
> +++ b/gcc/dse.cc
> @@ -251,6 +251,9 @@ public:
> and known (rather than -1). */
> poly_int64 width;
>
> + /* The address space that the memory reference uses. */
> + unsigned char addrspace;
> +
> union
> {
> /* A bitmask as wide as the number of bytes in the word that
> @@ -1524,6 +1527,7 @@ record_store (rtx body, bb_info_t bb_info)
> ptr = active_local_stores;
> last = NULL;
> redundant_reason = NULL;
> + unsigned char addrspace = MEM_ADDR_SPACE (mem);
> mem = canon_rtx (mem);
>
> if (group_id < 0)
> @@ -1548,7 +1552,9 @@ record_store (rtx body, bb_info_t bb_info)
> while (!s_info->is_set)
> s_info = s_info->next;
>
> - if (s_info->group_id == group_id && s_info->cse_base == base)
> + if (s_info->group_id == group_id
> + && s_info->cse_base == base
> + && s_info->addrspace == addrspace)
> {
> HOST_WIDE_INT i;
> if (dump_file && (dump_flags & TDF_DETAILS))
> @@ -1688,6 +1694,7 @@ record_store (rtx body, bb_info_t bb_info)
> store_info->rhs = rhs;
> store_info->const_rhs = const_rhs;
> store_info->redundant_reason = redundant_reason;
> + store_info->addrspace = addrspace;
>
> /* If this is a clobber, we return 0. We will only be able to
> delete this insn if there is only one store USED store, but we
> diff --git a/gcc/testsuite/gcc.target/i386/addr-space-6.c
> b/gcc/testsuite/gcc.target/i386/addr-space-6.c
> new file mode 100644
> index 00000000000..82eca4d7e0c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/addr-space-6.c
> @@ -0,0 +1,21 @@
> +/* PR rtl-optimization/102733 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1" } */
> +
> +/* DSE was removing a store to fs:0 (correctly)
> + and gs:0 (incorrectly) as DSE didn't take into
> + account the address space was different. */
> +
> +void test_null_store (void)
> +{
> + int __seg_fs *fs = (int __seg_fs *)0;
> + *fs = 1;
> +
> + int __seg_gs *gs = (int __seg_gs *)0;
> + *gs = 2;
> + *fs = 3;
> +}
> +
> +/* { dg-final { scan-assembler-times "movl\t" 2 } } */
> +/* { dg-final { scan-assembler "gs:" } } */
> +/* { dg-final { scan-assembler "fs:" } } */
> --
> 2.31.1
>
