Re: [PATCH] RISC-V: bitmanip: use bexti for "(a & (1 << BIT_NO)) ? 0 : -1"

2022-11-17 Thread Philipp Tomsich 
Committed to master. Thanks!
Philipp.

On Thu, 17 Nov 2022 at 15:43, Jeff Law  wrote:
>
>
> On 11/8/22 12:55, Philipp Tomsich 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:
> >   andia0,a0,16
> >   seqza0,a0
> >   neg a0,a0
> >   ret
> > Following this change, it results in:
> >   bexti   a0,a0,4
> >   addia0,a0,-1
> >   ret
> >
> > 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.
>
> OK
>
>
> Jeff
>
>

Re: [PATCH] RISC-V: bitmanip: use bexti for "(a & (1 << BIT_NO)) ? 0 : -1"

2022-11-17 Thread Jeff Law via Gcc-patches 



On 11/8/22 12:55, Philipp Tomsich 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:
andia0,a0,16
seqza0,a0
neg a0,a0
ret
Following this change, it results in:
bexti   a0,a0,4
addia0,a0,-1
ret

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.


OK


Jeff

[PATCH] RISC-V: bitmanip: use bexti for "(a & (1 << BIT_NO)) ? 0 : -1"

2022-11-08 Thread Philipp Tomsich 
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:
andia0,a0,16
seqza0,a0
neg a0,a0
ret
Following this change, it results in:
bexti   a0,a0,4
addia0,a0,-1
ret

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 d26f3567182..30dabdf8ddc 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -394,3 +394,16 @@
   "TARGET_ZBS && UINTVAL (operands[2]) < GET_MODE_BITSIZE (mode)"
   "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 000..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