On Thu, Aug 31, 2023 at 11:18 AM Jakub Jelinek via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Thu, Aug 31, 2023 at 04:20:17PM +0800, Hongyu Wang via Gcc-patches wrote:
> > From: Kong Lingling <lingling.k...@intel.com>
> >
> > In inline asm, we do not know if the insn can use EGPR, so disable EGPR
> > usage by default from mapping the common reg/mem constraint to non-EGPR
> > constraints. Use a flag mapx-inline-asm-use-gpr32 to enable EGPR usage
> > for inline asm.
> >
> > gcc/ChangeLog:
> >
> > * config/i386/i386.cc (INCLUDE_STRING): Add include for
> > ix86_md_asm_adjust.
> > (ix86_md_asm_adjust): When APX EGPR enabled without specifying the
> > target option, map reg/mem constraints to non-EGPR constraints.
> > * config/i386/i386.opt: Add option mapx-inline-asm-use-gpr32.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.target/i386/apx-inline-gpr-norex2.c: New test.
> > ---
> > gcc/config/i386/i386.cc | 44 +++++++
> > gcc/config/i386/i386.opt | 5 +
> > .../gcc.target/i386/apx-inline-gpr-norex2.c | 107 ++++++++++++++++++
> > 3 files changed, 156 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.target/i386/apx-inline-gpr-norex2.c
> >
> > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> > index d26d9ab0d9d..9460ebbfda4 100644
> > --- a/gcc/config/i386/i386.cc
> > +++ b/gcc/config/i386/i386.cc
> > @@ -17,6 +17,7 @@ You should have received a copy of the GNU General Public
> > License
> > along with GCC; see the file COPYING3. If not see
> > <http://www.gnu.org/licenses/>. */
> >
> > +#define INCLUDE_STRING
> > #define IN_TARGET_CODE 1
> >
> > #include "config.h"
> > @@ -23077,6 +23078,49 @@ ix86_md_asm_adjust (vec<rtx> &outputs, vec<rtx> &
> > /*inputs*/,
> > bool saw_asm_flag = false;
> >
> > start_sequence ();
> > + /* TODO: Here we just mapped the general r/m constraints to non-EGPR
> > + constraints, will eventually map all the usable constraints in the
> > future. */
>
> I think there should be some constraint which explicitly has all the 32
> GPRs, like there is one for just all 16 GPRs (h), so that regardless of
> -mapx-inline-asm-use-gpr32 one can be explicit what the inline asm wants.
>
> Also, what about the "g" constraint? Shouldn't there be another for "g"
> without r16..r31? What about the various other memory
> constraints ("<", "o", ...)?
I think we should leave all existing constraints as they are, so "r"
covers only GPR16, "m" and "o" to only use GPR16. We can then
introduce "h" to instructions that have the ability to handle EGPR.
This would be somehow similar to the SSE -> AVX512F transition, where
we still have "x" for SSE16 and "v" was introduced as a separate
register class for EVEX SSE registers. This way, asm will be
compatible, when "r", "m", "o" and "g" are used. The new memory
constraint "Bt", should allow new registers, and should be added to
the constraint string as a separate constraint, and conditionally
enabled by relevant "isa" (AKA "enabled") attribute.
Uros.
> > + if (TARGET_APX_EGPR && !ix86_apx_inline_asm_use_gpr32)
> > + {
> > + /* Map "r" constraint in inline asm to "h" that disallows r16-r31
> > + and replace only r, exclude Br and Yr. */
> > + for (unsigned i = 0; i < constraints.length (); i++)
> > + {
> > + std::string *s = new std::string (constraints[i]);
>
> Doesn't this leak memory (all the time)?
> I must say I don't really understand why you need to use std::string here,
> but certainly it shouldn't leak.
>
> > + size_t pos = s->find ('r');
> > + while (pos != std::string::npos)
> > + {
> > + if (pos > 0
> > + && (s->at (pos - 1) == 'Y' || s->at (pos - 1) == 'B'))
> > + pos = s->find ('r', pos + 1);
> > + else
> > + {
> > + s->replace (pos, 1, "h");
> > + constraints[i] = (const char*) s->c_str ();
>
> Formatting (space before *). The usual way for constraints is ggc_strdup on
> some string in a buffer. Also, one could have several copies or r (or m,
> memory (doesn't
> that appear just in clobbers? And that doesn't look like something that
> should be replaced), Bm, e.g. in various alternatives. So, you
> need to change them all, not just the first hit. "r,r,r,m" and the like.
> Normally, one would simply walk the constraint string, parsing the special
> letters (+, =, & etc.) and single letter constraints and 2 letter
> constraints using CONSTRAINT_LEN macro (tons of examples in GCC sources).
> Either do it in 2 passes, first one counts how long constraint string one
> will need after the adjustments (and whether to adjust something at all),
> then if needed XALLOCAVEC it and adjust in there, or say use a
> auto_vec<char, 32> for
> it.
>
> > + break;
> > + }
> > + }
> > + }
> > + /* Also map "m/memory/Bm" constraint that may use GPR32, replace
> > them with
> > + "Bt/Bt/BT". */
> > + for (unsigned i = 0; i < constraints.length (); i++)
> > + {
> > + std::string *s = new std::string (constraints[i]);
> > + size_t pos = s->find ("m");
> > + size_t pos2 = s->find ("memory");
> > + if (pos != std::string::npos)
> > + {
> > + if (pos > 0 && (s->at (pos - 1) == 'B'))
> > + s->replace (pos - 1, 2, "BT");
> > + else if (pos2 != std::string::npos)
> > + s->replace (pos, 6, "Bt");
> > + else
> > + s->replace (pos, 1, "Bt");
>
> Formatting, the s->replace calls are indented too much.
>
> Jakub
>
