> -----Original Message-----
> From: Gcc-patches <gcc-patches-boun...@gcc.gnu.org> On Behalf Of
> Szabolcs Nagy
> Sent: 26 June 2020 15:44
> To: gcc-patches@gcc.gnu.org
> Cc: fwei...@redhat.com; Richard Earnshaw <richard.earns...@arm.com>;
> Daniel Kiss <daniel.k...@arm.com>
> Subject: Re: [PATCH 1/4] aarch64: fix return address access with pac
> [PR94891][PR94791]
>
> The 06/05/2020 17:51, Szabolcs Nagy wrote:
> > This is a big hammer fix for __builtin_return_address (PR target/94891)
> > returning signed addresses (sometimes, depending on wether lr happens
> > to be signed or not at the time of call which depends on optimizations),
> > and similarly -pg may pass signed return address to _mcount
> > (PR target/94791).
> >
> > At the time of return address expansion we don't know if it's signed or
> > not so it is done unconditionally.
> >
> > I wonder if allocate_initial_value for the lr reg may solve this better
> > such that get_hard_reg_initial_val just gives the right (unsigned) value?
> >
> > 2020-06-04 Szabolcs Nagy <szabolcs.n...@arm.com>
> >
> > * config/aarch64/aarch64-protos.h (aarch64_return_addr_rtx):
> Declare.
> > * config/aarch64/aarch64.c (aarch64_return_addr_rtx): New.
> > (aarch64_return_addr): Use aarch64_return_addr_rtx.
> > * config/aarch64/aarch64.h (PROFILE_HOOK): Likewise.
>
> ping.
>
This looks ok to me.
Thanks,
Kyrill
> (this fixes a correctness bug in pac-ret, tested with no regressions).
>
> > ---
> > gcc/config/aarch64/aarch64-protos.h | 1 +
> > gcc/config/aarch64/aarch64.c | 20 +++++++++++++++++++-
> > gcc/config/aarch64/aarch64.h | 2 +-
> > 3 files changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/gcc/config/aarch64/aarch64-protos.h
> b/gcc/config/aarch64/aarch64-protos.h
> > index 9e43adb7db0..723d9ba6ac6 100644
> > --- a/gcc/config/aarch64/aarch64-protos.h
> > +++ b/gcc/config/aarch64/aarch64-protos.h
> > @@ -578,6 +578,7 @@ int aarch64_vec_fpconst_pow_of_2 (rtx);
> > rtx aarch64_eh_return_handler_rtx (void);
> > rtx aarch64_mask_from_zextract_ops (rtx, rtx);
> > const char *aarch64_output_move_struct (rtx *operands);
> > +rtx aarch64_return_addr_rtx (void);
> > rtx aarch64_return_addr (int, rtx);
> > rtx aarch64_simd_gen_const_vector_dup (machine_mode,
> HOST_WIDE_INT);
> > bool aarch64_simd_mem_operand_p (rtx);
> > diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> > index 6352d4ff78a..6a2f85c4af7 100644
> > --- a/gcc/config/aarch64/aarch64.c
> > +++ b/gcc/config/aarch64/aarch64.c
> > @@ -10819,6 +10819,24 @@ aarch64_initial_elimination_offset (unsigned
> from, unsigned to)
> > return cfun->machine->frame.frame_size;
> > }
> >
> > +
> > +/* Get return address without mangling. */
> > +
> > +rtx
> > +aarch64_return_addr_rtx (void)
> > +{
> > + rtx val = get_hard_reg_initial_val (Pmode, LR_REGNUM);
> > + /* Note: aarch64_return_address_signing_enabled only
> > + works after cfun->machine->frame.laid_out is set,
> > + so here we don't know if the return address will
> > + be signed or not. */
> > + rtx lr = gen_rtx_REG (Pmode, LR_REGNUM);
> > + emit_move_insn (lr, val);
> > + emit_insn (GEN_FCN (CODE_FOR_xpaclri) ());
> > + return lr;
> > +}
> > +
> > +
> > /* Implement RETURN_ADDR_RTX. We do not support moving back to a
> > previous frame. */
> >
> > @@ -10827,7 +10845,7 @@ aarch64_return_addr (int count, rtx frame
> ATTRIBUTE_UNUSED)
> > {
> > if (count != 0)
> > return const0_rtx;
> > - return get_hard_reg_initial_val (Pmode, LR_REGNUM);
> > + return aarch64_return_addr_rtx ();
> > }
> >
> >
> > diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
> > index 2be52fd4d73..f11941bbc86 100644
> > --- a/gcc/config/aarch64/aarch64.h
> > +++ b/gcc/config/aarch64/aarch64.h
> > @@ -1112,7 +1112,7 @@ typedef struct
> > #define PROFILE_HOOK(LABEL)
> \
> > {
> > \
> > rtx fun, lr; \
> > - lr = get_hard_reg_initial_val (Pmode, LR_REGNUM);
> \
> > + lr = aarch64_return_addr_rtx ();
> > \
> > fun = gen_rtx_SYMBOL_REF (Pmode, MCOUNT_NAME);
> \
> > emit_library_call (fun, LCT_NORMAL, VOIDmode, lr, Pmode);
> \
> > }
> > --
> > 2.17.1
> >
>
> --
