Hi all,
On Sat, Mar 23, 2019 at 11:46:12PM +0000, Segher Boessenkool wrote:
> CSE does not consider calls, not even const calls. This patch puts a
> REG_EQUAL note on the pseudo we assign the __tls_get_addr result to,
> so that those pseudos can be CSE'd and the extra calls deleted as dead
> code.
>
> CSE should really handle const calls directly, but it is stage 4.
I am backporting this to GCC 8.
Segher
> 2019-03-23 Segher Boessenkool <seg...@kernel.crashing.org>
>
> * config/rs6000/rs6000.c (rs6000_legitimize_tls_address): Add REG_EQUAL
> notes for the result of the __tls_get_addr calls.
> * config/rs6000/rs6000.md (unspec UNSPEC_TLS_GET_ADDR): New.
>
> ---
> gcc/config/rs6000/rs6000.c | 10 ++++++++++
> gcc/config/rs6000/rs6000.md | 1 +
> 2 files changed, 11 insertions(+)
>
> diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
> index 15811bd..35aedf4 100644
> --- a/gcc/config/rs6000/rs6000.c
> +++ b/gcc/config/rs6000/rs6000.c
> @@ -8661,6 +8661,11 @@ rs6000_legitimize_tls_address (rtx addr, enum
> tls_model model)
> else
> emit_library_call_value (tga, dest, LCT_CONST, Pmode);
> global_tlsarg = NULL_RTX;
> +
> + /* Make a note so that the result of this call can be CSEd. */
> + rtvec vec = gen_rtvec (1, copy_rtx (arg));
> + rtx uns = gen_rtx_UNSPEC (Pmode, vec, UNSPEC_TLS_GET_ADDR);
> + set_unique_reg_note (get_last_insn (), REG_EQUAL, uns);
> }
> else if (model == TLS_MODEL_LOCAL_DYNAMIC)
> {
> @@ -8679,6 +8684,11 @@ rs6000_legitimize_tls_address (rtx addr, enum
> tls_model model)
> emit_library_call_value (tga, tmp1, LCT_CONST, Pmode);
> global_tlsarg = NULL_RTX;
>
> + /* Make a note so that the result of this call can be CSEd. */
> + rtvec vec = gen_rtvec (1, copy_rtx (arg));
> + rtx uns = gen_rtx_UNSPEC (Pmode, vec, UNSPEC_TLS_GET_ADDR);
> + set_unique_reg_note (get_last_insn (), REG_EQUAL, uns);
> +
> if (rs6000_tls_size == 16)
> {
> if (TARGET_64BIT)
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index f2faef8..815077c 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -79,6 +79,7 @@ (define_c_enum "unspec"
> UNSPEC_MPIC_CORRECT ; macho_correct_pic
> UNSPEC_TLSGD
> UNSPEC_TLSLD
> + UNSPEC_TLS_GET_ADDR
> UNSPEC_MOVESI_FROM_CR
> UNSPEC_MOVESI_TO_CR
> UNSPEC_TLSDTPREL
> --
> 1.8.3.1
