On Mon, May 31, 2021 at 3:12 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> On Mon, May 31, 2021 at 5:46 AM Richard Biener
> <richard.guent...@gmail.com> wrote:
> >
> > On Mon, May 31, 2021 at 2:09 PM H.J. Lu <hjl.to...@gmail.com> wrote:
> > >
> > > On Wed, May 26, 2021 at 10:28:16AM +0200, Richard Biener wrote:
> > > > > > >
> > > > > > > -- Target Hook: rtx TARGET_GEN_MEMSET_VALUE (rtx DATA,
> > > > > > > scalar_int_mode
> > > > > > > MODE)
> > > > > > > This function returns the RTL of a register containing
> > > > > > > 'GET_MODE_SIZE (MODE)' consecutive copies of the unsigned
> > > > > > > char
> > > > > > > value given in the RTL register DATA. For example, if MODE
> > > > > > > is 4
> > > > > > > bytes wide, return the RTL for 0x01010101*DATA.
> > > > > >
> > > > > > For this one I wonder if it should be an optab instead. Couldn't
> > > > > > you
> > > > > > use the existing vec_duplicate for this by using (paradoxical)
> > > > > > subregs
> > > > > > like (subreg:TI (vec_duplicate:VnQI (subreg:VnQI (reg:QI ...)))?
> > > > >
> > > > > I tried. It doesn't even work on x86. See:
> > > > >
> > > > > https://gcc.gnu.org/pipermail/gcc-patches/2021-May/570661.html
> > > >
> > > > Not sure what I should read from there...
> > > >
> > > > > There are special cases to subreg HI, SI and DI modes of TI mode in
> > > > > ix86_gen_memset_value_from_prev. simplify_gen_subreg doesn't
> > > > > work here. Each backend may need its own special handling.
> > > >
> > > > OK, I guess I'm not (RTL) qualified enough to further review these
> > > > parts,
> > > > sorry. Since we're doing code generation the canonical way to
> > > > communicate
> > > > with backends should be optabs, not some set of disconnected target
> > > > hooks.
> > > > But as said, I probably don't know enough of RTL to see why it's the
> > > > only way.
> > > >
> > > > Richard.
> > >
> > > Here is the patch to add optabs instead. Does it look OK?
> > >
> > > Thanks.
> > >
> > > H.J.
> > > ---
> > > Add 2 optabs:
> > >
> > > 1. integer_extract: Extract lower bit value from the integer value in
> > > TImode, OImode or XImode.
> >
> > That sounds very specific, esp. the restriction to {TI,OI,XI}mode.
> > It also sounds like it matches (subreg:{TI,OI,XI} (...) 0). There are
> > existing target hooks verifying subreg validity - why's that not a good
> > fit here? ISTR you say gen_lowpart () doesn't work (or was it
> > simplify_gen_subreg?), why's that so?
>
> {TI,OI,XI}mode are storage only integer types. subreg doesn't work
> well on them. I got
>
> [hjl@gnu-cfl-2 pieces]$ cat s2.i
> extern void *ops;
>
> void
> foo (int c)
> {
> __builtin_memset (ops, c, 34);
> }
> [hjl@gnu-cfl-2 pieces]$ make s2.s
> /export/build/gnu/tools-build/gcc-gitlab-debug/build-x86_64-linux/gcc/xgcc
> -B/export/build/gnu/tools-build/gcc-gitlab-debug/build-x86_64-linux/gcc/
> -O2 -march=haswell -S s2.i
> during RTL pass: reload
> s2.i: In function ‘foo’:
> s2.i:7:1: internal compiler error: maximum number of generated reload
> insns per insn achieved (90)
> 7 | }
> | ^
> 0x1050734 lra_constraints(bool)
> /export/gnu/import/git/gitlab/x86-gcc/gcc/lra-constraints.c:5091
> 0x1039536 lra(_IO_FILE*)
> /export/gnu/import/git/gitlab/x86-gcc/gcc/lra.c:2336
> 0xfe1140 do_reload
> /export/gnu/import/git/gitlab/x86-gcc/gcc/ira.c:5822
> 0xfe162e execute
> /export/gnu/import/git/gitlab/x86-gcc/gcc/ira.c:6008
> Please submit a full bug report,
> with preprocessed source if appropriate.
> Please include the complete backtrace with any bug report.
> See <https://gcc.gnu.org/bugs/> for instructions.
> make: *** [Makefile:32: s2.s] Error 1
> [hjl@gnu-cfl-2 pieces]$
>
> due to
>
> (insn 12 11 0 (set (mem:HI (plus:DI (reg/f:DI 84)
> (const_int 32 [0x20])) [0 MEM <char[1:34]> [(void
> *)ops.0_1]+32 S2 A8])
> (subreg:HI (reg:OI 51 xmm15) 0)) "s2.i":6:3 -1
> (nil))
>
> The new optab gives us
>
> (insn 12 11 13 2 (set (reg:TI 88)
> (reg:TI 51 xmm15)) "s2.i":6:3 -1
> (nil))
> (insn 13 12 14 2 (set (reg:SI 89)
> (subreg:SI (reg:TI 88) 0)) "s2.i":6:3 -1
> (nil))
> (insn 14 13 15 2 (set (reg:HI 87)
> (subreg:HI (reg:SI 89) 0)) "s2.i":6:3 -1
> (nil))
that looks odd to me - what's the final result after LRA? I think
we should see to make lowpart_subreg work on {XI,OI,TI}mode.
Only two steps should be necessary at most:
xmm -> gpr, grp -> subreg, or gpr -> subreg. So the expander
code in memset should try to generate the subreg directly
and if that fails, try a word_mode subreg followed by the subreg.
> (insn 15 14 0 2 (set (mem:HI (plus:DI (reg/f:DI 84)
> (const_int 32 [0x20])) [0 MEM <char[1:34]> [(void
> *)ops.0_1]+32 S2 A8])
> (reg:HI 87)) "s2.i":6:3 -1
> (nil))
>
> > > 2. vec_const_duplicate: Broadcast a QImode constant to a vector. It is
> > > similar to vec_duplicate. Since the resulting vector is computable at
> > > compile-time, vec_duplicate may not be faster and backend can opt out
> > > broadcasting from a constant while opting in broadcasting from a
> > > variable.
> >
> > Is it for the latter that you choose to use a new optab since
> > vec_duplicate is not allowed to FAIL? You should probably document
>
> Yes.
>
> > that the constant value duplicated should be of the component mode of
> > m.
>
> I added:
>
> @cindex @code{vec_const_duplicate@var{m}} instruction pattern
> @item @samp{vec_const_duplicate@var{m}}
> Initialize vector output operand 0 in mode @var{m} so that each element
> has the value given by constant input operand 1.
>
> This pattern only handles duplicates of constant inputs. Non-constant
> vectors go through the @code{vec_duplicate@var{m}} pattern instead.
>
> This pattern is not allowed to @code{FAIL}.
>
> which is in my patch.
>
> > > and rewrite builtin_memset_read_str/builtin_memset_gen_str to support
> > > target instructions to duplicate QImode value to TImode, OImode or XImode
> > > value for memmset.
> > >
> > > Add TARGET_GEN_MEMSET_SCRATCH_RTX to allow the backend to use a hard
> > > scratch register to avoid stack realignment when expanding memset.
> > >
> > > PR middle-end/90773
> > > * builtins.c (gen_memset_value_from_prev): New function.
> > > (gen_memset_broadcast): Likewise.
> > > (builtin_memset_read_str): Use gen_memset_value_from_prev
> > > and gen_memset_broadcast.
> > > (builtin_memset_gen_str): Likewise.
> > > * optabs.def: Add integer_extract and vec_const_duplicate.
> > > * target.def (gen_memset_scratch_rtx): New hook.
> > > * doc/md.texi: Document vec_const_duplicate and integer_extract.
> > > * doc/tm.texi.in: Add TARGET_GEN_MEMSET_SCRATCH_RTX.
> > > * doc/tm.texi: Regenerated.
> > > ---
> > > gcc/builtins.c | 117 +++++++++++++++++++++++++++++++++++++--------
> > > gcc/doc/md.texi | 16 +++++++
> > > gcc/doc/tm.texi | 5 ++
> > > gcc/doc/tm.texi.in | 2 +
> > > gcc/optabs.def | 4 ++
> > > gcc/target.def | 7 +++
> > > 6 files changed, 131 insertions(+), 20 deletions(-)
> > >
> > > diff --git a/gcc/builtins.c b/gcc/builtins.c
> > > index af1fe49bb48..7683169eb96 100644
> > > --- a/gcc/builtins.c
> > > +++ b/gcc/builtins.c
> > > @@ -6598,26 +6598,106 @@ expand_builtin_strncpy (tree exp, rtx target)
> > > return NULL_RTX;
> > > }
> > >
> > > +/* Return the RTL of a register in MODE generated from PREV in the
> > > + previous iteration. */
> > > +
> > > +static rtx
> > > +gen_memset_value_from_prev (void *prevp, scalar_int_mode mode)
> > > +{
> > > + rtx target = nullptr;
> > > + by_pieces_prev *prev = (by_pieces_prev *) prevp;
> > > + if (prev != nullptr && prev->data != nullptr)
> > > + {
> > > + /* Use the previous data in the same mode. */
> > > + if (prev->mode == mode)
> > > + return prev->data;
> > > +
> > > + /* Extract the RTL in MODE from PREV. */
> > > + enum insn_code icode
> > > + = convert_optab_handler (integer_extract_optab, mode,
> > > + prev->mode);
> > > + if (icode != CODE_FOR_nothing)
> > > + {
> > > + target = gen_reg_rtx (mode);
> > > + class expand_operand ops[2];
> > > + create_output_operand (&ops[0], target, mode);
> > > + create_input_operand (&ops[1], prev->data, prev->mode);
> > > + expand_insn (icode, 2, ops);
> > > + if (!rtx_equal_p (target, ops[0].value))
> > > + emit_move_insn (target, ops[0].value);
> > > + }
> > > + else
> > > + target = simplify_gen_subreg (mode, prev->data, prev->mode, 0);
> > > + }
> > > + return target;
> > > +}
> > > +
> > > +/* Return the RTL of a register in MODE broadcasted from DATA. */
> > > +
> > > +static rtx
> > > +gen_memset_broadcast (enum optab_tag broadcast_optab, rtx data,
> > > + scalar_int_mode mode)
> > > +{
> > > + /* Skip if regno_reg_rtx isn't initialized. */
> > > + if (!regno_reg_rtx)
> > > + return nullptr;
> > > +
> > > + rtx target = nullptr;
> > > +
> > > + unsigned int nunits = GET_MODE_SIZE (mode) / GET_MODE_SIZE (QImode);
> > > + machine_mode vector_mode;
> > > + if (!mode_for_vector (QImode, nunits).exists (&vector_mode))
> > > + gcc_unreachable ();
> > > +
> > > + enum insn_code icode = optab_handler (broadcast_optab, vector_mode);
> > > + if (icode != CODE_FOR_nothing)
> > > + {
> > > + target = targetm.gen_memset_scratch_rtx (vector_mode);
> > > + class expand_operand ops[2];
> > > + create_output_operand (&ops[0], target, vector_mode);
> > > + create_input_operand (&ops[1], (rtx) data, QImode);
> > > + expand_insn (icode, 2, ops);
> > > + if (!rtx_equal_p (target, ops[0].value))
> > > + emit_move_insn (target, ops[0].value);
> > > + if (REGNO (target) < FIRST_PSEUDO_REGISTER)
> > > + target = gen_rtx_REG (mode, REGNO (target));
> > > + else
> > > + target = convert_to_mode (mode, target, 1);
> > > + }
> > > +
> > > + return target;
> > > +}
> > > +
> > > /* Callback routine for store_by_pieces. Read GET_MODE_BITSIZE (MODE)
> > > bytes from constant string DATA + OFFSET and return it as target
> > > constant. If PREV isn't nullptr, it has the RTL info from the
> > > previous iteration. */
> > >
> > > rtx
> > > -builtin_memset_read_str (void *data, void *prevp,
> > > +builtin_memset_read_str (void *data, void *prev,
> > > HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> > > scalar_int_mode mode)
> > > {
> > > - by_pieces_prev *prev = (by_pieces_prev *) prevp;
> > > - if (prev != nullptr && prev->data != nullptr)
> > > + rtx target;
> > > +
> > > + /* Don't use the previous value if size is 1. */
> > > + if (GET_MODE_SIZE (mode) != 1)
> > > {
> > > - /* Use the previous data in the same mode. */
> > > - if (prev->mode == mode)
> > > - return prev->data;
> > > + target = gen_memset_value_from_prev (prev, mode);
> > > + if (target != nullptr)
> > > + return target;
> > > }
> > >
> > > const char *c = (const char *) data;
> > > - char *p = XALLOCAVEC (char, GET_MODE_SIZE (mode));
> > > + char *p = XALLOCAVEC (char, GET_MODE_SIZE (QImode));
> > > + memset (p, *c, GET_MODE_SIZE (QImode));
> > > + rtx src = c_readstr (p, QImode);
> > > + target = gen_memset_broadcast (vec_const_duplicate_optab, src,
> > > + mode);
> > > + if (target != nullptr)
> > > + return target;
> > > +
> > > + p = XALLOCAVEC (char, GET_MODE_SIZE (mode));
> > >
> > > memset (p, *c, GET_MODE_SIZE (mode));
> > >
> > > @@ -6631,7 +6711,7 @@ builtin_memset_read_str (void *data, void *prevp,
> > > nullptr, it has the RTL info from the previous iteration. */
> > >
> > > static rtx
> > > -builtin_memset_gen_str (void *data, void *prevp,
> > > +builtin_memset_gen_str (void *data, void *prev,
> > > HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> > > scalar_int_mode mode)
> > > {
> > > @@ -6639,22 +6719,19 @@ builtin_memset_gen_str (void *data, void *prevp,
> > > size_t size;
> > > char *p;
> > >
> > > - by_pieces_prev *prev = (by_pieces_prev *) prevp;
> > > - if (prev != nullptr && prev->data != nullptr)
> > > - {
> > > - /* Use the previous data in the same mode. */
> > > - if (prev->mode == mode)
> > > - return prev->data;
> > > -
> > > - target = simplify_gen_subreg (mode, prev->data, prev->mode, 0);
> > > - if (target != nullptr)
> > > - return target;
> > > - }
> > > -
> > > size = GET_MODE_SIZE (mode);
> > > if (size == 1)
> > > return (rtx) data;
> > >
> > > + target = gen_memset_value_from_prev (prev, mode);
> > > + if (target != nullptr)
> > > + return target;
> > > +
> > > + target = gen_memset_broadcast (vec_duplicate_optab, (rtx) data,
> > > + mode);
> > > + if (target != nullptr)
> > > + return target;
> > > +
> > > p = XALLOCAVEC (char, size);
> > > memset (p, 1, size);
> > > coeff = c_readstr (p, mode);
> > > diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
> > > index 00caf3844cc..a798fb1a97e 100644
> > > --- a/gcc/doc/md.texi
> > > +++ b/gcc/doc/md.texi
> > > @@ -5079,6 +5079,16 @@ vectors go through the @code{mov@var{m}} pattern
> > > instead.
> > >
> > > This pattern is not allowed to @code{FAIL}.
> > >
> > > +@cindex @code{vec_const_duplicate@var{m}} instruction pattern
> > > +@item @samp{vec_const_duplicate@var{m}}
> > > +Initialize vector output operand 0 in mode @var{m} so that each element
> > > +has the value given by constant input operand 1.
> > > +
> > > +This pattern only handles duplicates of constant inputs. Non-constant
> > > +vectors go through the @code{vec_duplicate@var{m}} pattern instead.
> > > +
> > > +This pattern is not allowed to @code{FAIL}.
> > > +
> > > @cindex @code{vec_series@var{m}} instruction pattern
> > > @item @samp{vec_series@var{m}}
> > > Initialize vector output operand 0 so that element @var{i} is equal to
> > > @@ -7904,6 +7914,12 @@ inclusive and operand 1 exclusive.
> > > If this pattern is not defined, a call to the library function
> > > @code{__clear_cache} is used.
> > >
> > > +@cindex @code{integer_extract@var{m}@var{n}} instruction pattern
> > > +@item @samp{integer_extract@var{m}@var{n}}
> > > +Extract lower bit value from the integer value in @code{TImode},
> > > +@code{OImode} or @code{XImode}. Operand 1 is the integer in mode
> > > +@var{n} and operand 0 stores value to be extracted in mode @var{m}.
> > > +
> > > @end table
> > >
> > > @end ifset
> > > diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> > > index e3a080e4a7c..8ccc262b1fc 100644
> > > --- a/gcc/doc/tm.texi
> > > +++ b/gcc/doc/tm.texi
> > > @@ -11894,6 +11894,11 @@ This function prepares to emit a conditional
> > > comparison within a sequence
> > > @var{bit_code} is @code{AND} or @code{IOR}, which is the op on the
> > > compares.
> > > @end deftypefn
> > >
> > > +@deftypefn {Target Hook} rtx TARGET_GEN_MEMSET_SCRATCH_RTX (machine_mode
> > > @var{mode})
> > > +This hook should return an rtx for scratch register in @var{mode} to
> > > +be used by memset broadcast. The default is @code{gen_reg_rtx}.
> > > +@end deftypefn
> > > +
> > > @deftypefn {Target Hook} unsigned TARGET_LOOP_UNROLL_ADJUST (unsigned
> > > @var{nunroll}, class loop *@var{loop})
> > > This target hook returns a new value for the number of times @var{loop}
> > > should be unrolled. The parameter @var{nunroll} is the number of times
> > > diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> > > index d9fbbe20e6f..99bf01fe25d 100644
> > > --- a/gcc/doc/tm.texi.in
> > > +++ b/gcc/doc/tm.texi.in
> > > @@ -7960,6 +7960,8 @@ lists.
> > >
> > > @hook TARGET_GEN_CCMP_NEXT
> > >
> > > +@hook TARGET_GEN_MEMSET_SCRATCH_RTX
> > > +
> > > @hook TARGET_LOOP_UNROLL_ADJUST
> > >
> > > @defmac POWI_MAX_MULTS
> > > diff --git a/gcc/optabs.def b/gcc/optabs.def
> > > index b192a9d070b..fd8ab8b4a26 100644
> > > --- a/gcc/optabs.def
> > > +++ b/gcc/optabs.def
> > > @@ -100,6 +100,8 @@ OPTAB_CD(vec_init_optab, "vec_init$a$b")
> > >
> > > OPTAB_CD (while_ult_optab, "while_ult$a$b")
> > >
> > > +OPTAB_CD (integer_extract_optab, "integer_extract$a$b")
> > > +
> > > OPTAB_NL(add_optab, "add$P$a3", PLUS, "add", '3',
> > > gen_int_fp_fixed_libfunc)
> > > OPTAB_NX(add_optab, "add$F$a3")
> > > OPTAB_NX(add_optab, "add$Q$a3")
> > > @@ -453,3 +455,5 @@ OPTAB_DC (vec_series_optab, "vec_series$a",
> > > VEC_SERIES)
> > > OPTAB_D (vec_shl_insert_optab, "vec_shl_insert_$a")
> > > OPTAB_D (len_load_optab, "len_load_$a")
> > > OPTAB_D (len_store_optab, "len_store_$a")
> > > +
> > > +OPTAB_DC (vec_const_duplicate_optab, "vec_const_duplicate$a",
> > > VEC_DUPLICATE)
> > > diff --git a/gcc/target.def b/gcc/target.def
> > > index 1dffedc81e4..b89e7c24471 100644
> > > --- a/gcc/target.def
> > > +++ b/gcc/target.def
> > > @@ -2724,6 +2724,13 @@ DEFHOOK
> > > rtx, (rtx_insn **prep_seq, rtx_insn **gen_seq, rtx prev, int cmp_code,
> > > tree op0, tree op1, int bit_code),
> > > NULL)
> > >
> > > +DEFHOOK
> > > +(gen_memset_scratch_rtx,
> > > + "This hook should return an rtx for scratch register in @var{mode} to\n\
> > > +be used by memset broadcast. The default is @code{gen_reg_rtx}.",
> > > + rtx, (machine_mode mode),
> > > + gen_reg_rtx)
> > > +
> > > /* Return a new value for loop unroll size. */
> > > DEFHOOK
> > > (loop_unroll_adjust,
> > > --
> > > 2.31.1
> > >
>
>
>
> --
> H.J.
