Hi Philipp:
This patch series is LGTM, but plz introduce new pseudo when
can_create_pseudo_p like what we discussed in
https://gcc.gnu.org/pipermail/gcc-patches/2022-June/596305.html, you
can commit with the change with a [committed] patch mail :)
On Thu, Jun 16, 2022 at 5:32 PM Philipp Tomsich
<philipp.toms...@vrull.eu> wrote:
>
> Kito,
>
> Looks like this series fell by the wayside (possibly, because it
> didn't have a cover-letter and was easier to miss)?
>
> Thanks,
> Philipp.
>
> On Wed, 25 May 2022 at 00:52, Philipp Tomsich <philipp.toms...@vrull.eu>
> wrote:
> >
> > Consider creating a polarity-reversed mask from a set-bit (i.e., if
> > the bit is set, produce all-ones; otherwise: all-zeros). Using Zbb,
> > this can be expressed as bexti, followed by an addi of minus-one. To
> > enable the combiner to discover this opportunity, we need to split the
> > canonical expression for "(a & (1 << BIT_NO)) ? 0 : -1" into a form
> > combinable into bexti.
> >
> > Consider the function:
> > long f(long a)
> > {
> > return (a & (1 << BIT_NO)) ? 0 : -1;
> > }
> > This produces the following sequence prior to this change:
> > andi a0,a0,16
> > seqz a0,a0
> > neg a0,a0
> > ret
> > Following this change, it results in:
> > bexti a0,a0,4
> > addi a0,a0,-1
> > ret
> >
> > Signed-off-by: Philipp Tomsich <philipp.toms...@vrull.eu>
> >
> > gcc/ChangeLog:
> >
> > * config/riscv/bitmanip.md: Add a splitter to generate
> > polarity-reversed masks from a set bit using bexti + addi.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.target/riscv/zbs-bexti.c: New test.
> >
> > ---
> >
> > gcc/config/riscv/bitmanip.md | 13 +++++++++++++
> > gcc/testsuite/gcc.target/riscv/zbs-bexti.c | 14 ++++++++++++++
> > 2 files changed, 27 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.target/riscv/zbs-bexti.c
> >
> > diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
> > index 0ab9ffe3c0b..ea5dea13cfb 100644
> > --- a/gcc/config/riscv/bitmanip.md
> > +++ b/gcc/config/riscv/bitmanip.md
> > @@ -340,3 +340,16 @@ (define_insn "*bexti"
> > "TARGET_ZBS"
> > "bexti\t%0,%1,%2"
> > [(set_attr "type" "bitmanip")])
> > +
> > +;; We can create a polarity-reversed mask (i.e. bit N -> { set = 0, clear
> > = -1 })
> > +;; using a bext(i) followed by an addi instruction.
> > +;; This splits the canonical representation of "(a & (1 << BIT_NO)) ? 0 :
> > -1".
> > +(define_split
> > + [(set (match_operand:GPR 0 "register_operand")
> > + (neg:GPR (eq:GPR (zero_extract:GPR (match_operand:GPR 1
> > "register_operand")
> > + (const_int 1)
> > + (match_operand 2))
> > + (const_int 0))))]
> > + "TARGET_ZBS"
> > + [(set (match_dup 0) (zero_extract:GPR (match_dup 1) (const_int 1)
> > (match_dup 2)))
> > + (set (match_dup 0) (plus:GPR (match_dup 0) (const_int -1)))])
> > diff --git a/gcc/testsuite/gcc.target/riscv/zbs-bexti.c
> > b/gcc/testsuite/gcc.target/riscv/zbs-bexti.c
> > new file mode 100644
> > index 00000000000..99e3b58309c
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/riscv/zbs-bexti.c
> > @@ -0,0 +1,14 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-march=rv64gc_zbs -mabi=lp64 -O2" } */
> > +
> > +/* bexti */
> > +#define BIT_NO 4
> > +
> > +long
> > +foo0 (long a)
> > +{
> > + return (a & (1 << BIT_NO)) ? 0 : -1;
> > +}
> > +
> > +/* { dg-final { scan-assembler "bexti" } } */
> > +/* { dg-final { scan-assembler "addi" } } */
> > --
> > 2.34.1
> >
