On Wed, 2021-03-03 at 13:02 -0700, Jeff Law wrote:
>
>
> On 3/2/21 4:50 PM, Ilya Leoshkevich via Gcc-patches wrote:
> > Hello,
> >
> > I would like to ping the following patch:
> >
> > Add input_modes parameter to TARGET_MD_ASM_ADJUST hook
> > https://gcc.gnu.org/pipermail/gcc-patches/2021-January/562898.html
> >
> > It is needed for the following regression fix:
> >
> > IBM Z: Fix usage of "f" constraint with long doubles
> > https://gcc.gnu.org/pipermail/gcc-patches/2021-January/564380.html
> >
> >
> > Jakub, who would be the right person to review this change? I've
> > decided to ask you, since `git shortlog -ns gcc/cfgexpand.c` shows
> > that
> > you deal with this code a lot.
> >
> > Best regards,
> > Ilya
> >
> >
> >
> >
> > If TARGET_MD_ASM_ADJUST changes a mode of an input operand (which
> > should be ok as long as the hook itself as well as after_md_seq
> > make up
> > for it), input_mode will contain stale information.
> >
> > It might be tempting to fix this by removing input_mode altogether
> > and
> > just using GET_MODE (), but this will not work correctly with
> > constants.
> > So add input_modes parameter and document that it should be updated
> > whenever inputs parameter is updated.
> >
> > gcc/ChangeLog:
> >
> > 2021-01-05 Ilya Leoshkevich <i...@linux.ibm.com>
> >
> > * cfgexpand.c (expand_asm_loc): Pass new parameter.
> > (expand_asm_stmt): Likewise.
> > * config/arm/aarch-common-protos.h (arm_md_asm_adjust): Add
> > new
> > parameter.
> > * config/arm/aarch-common.c (arm_md_asm_adjust): Likewise.
> > * config/arm/arm.c (thumb1_md_asm_adjust): Likewise.
> > * config/cris/cris.c (cris_md_asm_adjust): Likewise.
> > * config/i386/i386.c (ix86_md_asm_adjust): Likewise.
> > * config/mn10300/mn10300.c (mn10300_md_asm_adjust):
> > Likewise.
> > * config/nds32/nds32.c (nds32_md_asm_adjust): Likewise.
> > * config/pdp11/pdp11.c (pdp11_md_asm_adjust): Likewise.
> > * config/rs6000/rs6000.c (rs6000_md_asm_adjust): Likewise.
> > * config/vax/vax.c (vax_md_asm_adjust): Likewise.
> > * config/visium/visium.c (visium_md_asm_adjust): Likewise.
> > * target.def (md_asm_adjust): Likewise.
> Ugh. A couple questions
> Are there any cases where you're going to want to change modes for
> arguments that were constants? I'm a bit surprised that we don't
> have
> a mode for constants for the cases that we care about. Presumably we
> can get a (modeless) CONST_INT here and we're not restricted to
> CONST_DOUBLE and friends (which have modes).
Yes, this might happen. For example, here:
asm("sqxbr\t%0,%1" : "=f"(res) : "f"(0x1.0000000000001p+0L));
the (const_double) and the corresponding operand will initially have
the mode TFmode. s390_md_asm_adjust () will add a conversion from
TFmode to FPRX2mode and change the argument accordingly.
However, this is not the problematic case that I refer to in the
commit message: I caught some failures in the testsuite that I
tracked down to (const_int)s, which, like you mentioned, don't have
a mode.
> Is input_modes read after the call to md_asm_adjust? I'm trying to
> figure out why we'd need to update it.
Yes, its contents goes into (asm_operand)'s (asm_input). If we don't
adjust it, (asm_input)s will no longer be consistent with input operand
RTXes.
> Not acking or naking at this point, I just want to make sure I
> understand what's going on.
>
> jeff
