[PATCH v2] aarch64: Add vector popcount besides QImode [PR113859]

[PATCH v2] aarch64: Add vector popcount besides QImode [PR113859]

[Pengxuan Zheng]

This patch improves GCC’s vectorization of __builtin_popcount for aarch64 target
by adding popcount patterns for vector modes besides QImode, i.e., HImode,
SImode and DImode.

With this patch, we now generate the following for V8HI:
  cnt     v1.16b, v.16b
  uaddlp  v2.8h, v1.16b

For V4HI, we generate:
  cnt     v1.8b, v.8b
  uaddlp  v2.4h, v1.8b

For V4SI, we generate:
  cnt     v1.16b, v.16b
  uaddlp  v2.8h, v1.16b
  uaddlp  v3.4s, v2.8h

For V2SI, we generate:
  cnt     v1.8b, v.8b
  uaddlp  v2.4h, v1.8b
  uaddlp  v3.2s, v2.4h

For V2DI, we generate:
  cnt     v1.16b, v.16b
  uaddlp  v2.8h, v1.16b
  uaddlp  v3.4s, v2.8h
  uaddlp  v4.2d, v3.4s

	PR target/113859

gcc/ChangeLog:

	* config/aarch64/aarch64-simd.md (aarch64_<su>addlp<mode>): Rename to...
	(@aarch64_<su>addlp<mode>): ... This.
	(popcount<mode>2): New define_expand.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/popcnt-vec.c: New test.
---
 gcc/config/aarch64/aarch64-simd.md            | 28 +++++++-
 gcc/testsuite/gcc.target/aarch64/popcnt-vec.c | 65 +++++++++++++++++++
 2 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/aarch64/popcnt-vec.c

diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
index 0bb39091a38..38dba285f69 100644
--- a/gcc/config/aarch64/aarch64-simd.md
+++ b/gcc/config/aarch64/aarch64-simd.md
@@ -3461,7 +3461,7 @@ (define_insn "*aarch64_<su>addlv<VDQV_L:mode>_ze<GPI:mode>"
   [(set_attr "type" "neon_reduc_add<VDQV_L:q>")]
 )
 
-(define_expand "aarch64_<su>addlp<mode>"
+(define_expand "@aarch64_<su>addlp<mode>"
   [(set (match_operand:<VDBLW> 0 "register_operand")
 	(plus:<VDBLW>
 	  (vec_select:<VDBLW>
@@ -3517,6 +3517,32 @@ (define_insn "popcount<mode>2<vczle><vczbe>"
   [(set_attr "type" "neon_cnt<q>")]
 )
 
+(define_expand "popcount<mode>2"
+  [(set (match_operand:VDQHSD 0 "register_operand")
+        (popcount:VDQHSD (match_operand:VDQHSD 1 "register_operand")))]
+  "TARGET_SIMD"
+  {
+    /* Generate a byte popcount. */
+    machine_mode mode = <bitsize> == 64 ? V8QImode : V16QImode;
+    rtx tmp = gen_reg_rtx (mode);
+    auto icode = optab_handler (popcount_optab, mode);
+    emit_insn (GEN_FCN (icode) (tmp, gen_lowpart (mode, operands[1])));
+
+    /* Use a sequence of UADDLPs to accumulate the counts. Each step doubles the
+       element size and halves the number of elements. */
+    do
+      {
+        auto icode = code_for_aarch64_addlp (ZERO_EXTEND, GET_MODE (tmp));
+        mode = insn_data[icode].operand[0].mode;
+        rtx dest = mode == <MODE>mode ? operands[0] : gen_reg_rtx (mode);
+        emit_insn (GEN_FCN (icode) (dest, tmp));
+        tmp = dest;
+      }
+    while (mode != <MODE>mode);
+    DONE;
+  }
+)
+
 ;; 'across lanes' max and min ops.
 
 ;; Template for outputting a scalar, so we can create __builtins which can be
diff --git a/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c b/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
new file mode 100644
index 00000000000..89860940296
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
@@ -0,0 +1,65 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+/* This function should produce cnt v.16b. */
+void
+bar (unsigned char *__restrict b, unsigned char *__restrict d)
+{
+  for (int i = 0; i < 1024; i++)
+    d[i] = __builtin_popcount (b[i]);
+}
+
+/* This function should produce cnt v.16b and uaddlp (Add Long Pairwise). */
+void
+bar1 (unsigned short *__restrict b, unsigned short *__restrict d)
+{
+  for (int i = 0; i < 1024; i++)
+    d[i] = __builtin_popcount (b[i]);
+}
+
+/* This function should produce cnt v.16b and 2 uaddlp (Add Long Pairwise). */
+void
+bar2 (unsigned int *__restrict b, unsigned int *__restrict d)
+{
+  for (int i = 0; i < 1024; i++)
+    d[i] = __builtin_popcount (b[i]);
+}
+
+/* This function should produce cnt v.16b and 3 uaddlp (Add Long Pairwise). */
+void
+bar3 (unsigned long long *__restrict b, unsigned long long *__restrict d)
+{
+  for (int i = 0; i < 1024; i++)
+    d[i] = __builtin_popcountll (b[i]);
+}
+
+/* This function should produce cnt v.8b and uaddlp (Add Long Pairwise). */
+void
+bar4 (unsigned short *__restrict b, unsigned short *__restrict d)
+{
+  for (int i = 0; i < 1028; i++)
+    d[i] = __builtin_popcount (b[i]);
+}
+
+/* This function should produce cnt v.8b and 2 uaddlp (Add Long Pairwise). */
+void
+bar5 (unsigned int *__restrict b, unsigned int *__restrict d)
+{
+  for (int i = 0; i < 1026; i++)
+    d[i] = __builtin_popcount (b[i]);
+}
+
+/* SLP
+ This function should produce cnt v.16b and 3 uaddlp (Add Long Pairwise). */
+void
+bar6 (unsigned long long *__restrict b, unsigned long long *__restrict d)
+{
+  d[0] = __builtin_popcountll (b[0]);
+  d[1] = __builtin_popcountll (b[1]);
+}
+
+/* { dg-final { scan-assembler-not {\tbl\tpopcount} } } */
+/* { dg-final { scan-assembler-times {cnt\t} 7 } } */
+/* { dg-final { scan-assembler-times {uaddlp\t} 12 } } */
+/* { dg-final { scan-assembler-times {ldr\tq} 5 } } */
+/* { dg-final { scan-assembler-times {ldr\td} 2 } } */
-- 
2.17.1

Re: [PATCH v2] aarch64: Add vector popcount besides QImode [PR113859]

[Richard Sandiford]

Pengxuan Zheng <quic_pzheng@quicinc.com> writes:
> This patch improves GCC’s vectorization of __builtin_popcount for aarch64 target
> by adding popcount patterns for vector modes besides QImode, i.e., HImode,
> SImode and DImode.
>
> With this patch, we now generate the following for V8HI:
>   cnt     v1.16b, v.16b
>   uaddlp  v2.8h, v1.16b
>
> For V4HI, we generate:
>   cnt     v1.8b, v.8b
>   uaddlp  v2.4h, v1.8b
>
> For V4SI, we generate:
>   cnt     v1.16b, v.16b
>   uaddlp  v2.8h, v1.16b
>   uaddlp  v3.4s, v2.8h
>
> For V2SI, we generate:
>   cnt     v1.8b, v.8b
>   uaddlp  v2.4h, v1.8b
>   uaddlp  v3.2s, v2.4h
>
> For V2DI, we generate:
>   cnt     v1.16b, v.16b
>   uaddlp  v2.8h, v1.16b
>   uaddlp  v3.4s, v2.8h
>   uaddlp  v4.2d, v3.4s
>
> 	PR target/113859
>
> gcc/ChangeLog:
>
> 	* config/aarch64/aarch64-simd.md (aarch64_<su>addlp<mode>): Rename to...
> 	(@aarch64_<su>addlp<mode>): ... This.
> 	(popcount<mode>2): New define_expand.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.target/aarch64/popcnt-vec.c: New test.
> ---
>  gcc/config/aarch64/aarch64-simd.md            | 28 +++++++-
>  gcc/testsuite/gcc.target/aarch64/popcnt-vec.c | 65 +++++++++++++++++++
>  2 files changed, 92 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
>
> diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
> index 0bb39091a38..38dba285f69 100644
> --- a/gcc/config/aarch64/aarch64-simd.md
> +++ b/gcc/config/aarch64/aarch64-simd.md
> @@ -3461,7 +3461,7 @@ (define_insn "*aarch64_<su>addlv<VDQV_L:mode>_ze<GPI:mode>"
>    [(set_attr "type" "neon_reduc_add<VDQV_L:q>")]
>  )
>  
> -(define_expand "aarch64_<su>addlp<mode>"
> +(define_expand "@aarch64_<su>addlp<mode>"
>    [(set (match_operand:<VDBLW> 0 "register_operand")
>  	(plus:<VDBLW>
>  	  (vec_select:<VDBLW>
> @@ -3517,6 +3517,32 @@ (define_insn "popcount<mode>2<vczle><vczbe>"
>    [(set_attr "type" "neon_cnt<q>")]
>  )
>  
> +(define_expand "popcount<mode>2"
> +  [(set (match_operand:VDQHSD 0 "register_operand")
> +        (popcount:VDQHSD (match_operand:VDQHSD 1 "register_operand")))]
> +  "TARGET_SIMD"
> +  {
> +    /* Generate a byte popcount. */
> +    machine_mode mode = <bitsize> == 64 ? V8QImode : V16QImode;
> +    rtx tmp = gen_reg_rtx (mode);
> +    auto icode = optab_handler (popcount_optab, mode);
> +    emit_insn (GEN_FCN (icode) (tmp, gen_lowpart (mode, operands[1])));
> +
> +    /* Use a sequence of UADDLPs to accumulate the counts. Each step doubles the
> +       element size and halves the number of elements. */

Nit: reflowing this paragraph has made the first line too long.
I think we should stick with the version in the review:

   /* Use a sequence of UADDLPs to accumulate the counts.  Each step doubles
      the element size and halves the number of elements.  */

> +    do
> +      {
> +        auto icode = code_for_aarch64_addlp (ZERO_EXTEND, GET_MODE (tmp));
> +        mode = insn_data[icode].operand[0].mode;
> +        rtx dest = mode == <MODE>mode ? operands[0] : gen_reg_rtx (mode);
> +        emit_insn (GEN_FCN (icode) (dest, tmp));
> +        tmp = dest;
> +      }
> +    while (mode != <MODE>mode);
> +    DONE;
> +  }
> +)
> +
>  ;; 'across lanes' max and min ops.
>  
>  ;; Template for outputting a scalar, so we can create __builtins which can be
> diff --git a/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c b/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
> new file mode 100644
> index 00000000000..89860940296
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
> @@ -0,0 +1,65 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +/* This function should produce cnt v.16b. */
> +void
> +bar (unsigned char *__restrict b, unsigned char *__restrict d)
> +{
> +  for (int i = 0; i < 1024; i++)
> +    d[i] = __builtin_popcount (b[i]);
> +}
> +
> +/* This function should produce cnt v.16b and uaddlp (Add Long Pairwise). */
> +void
> +bar1 (unsigned short *__restrict b, unsigned short *__restrict d)
> +{
> +  for (int i = 0; i < 1024; i++)
> +    d[i] = __builtin_popcount (b[i]);
> +}
> +
> +/* This function should produce cnt v.16b and 2 uaddlp (Add Long Pairwise). */
> +void
> +bar2 (unsigned int *__restrict b, unsigned int *__restrict d)
> +{
> +  for (int i = 0; i < 1024; i++)
> +    d[i] = __builtin_popcount (b[i]);
> +}
> +
> +/* This function should produce cnt v.16b and 3 uaddlp (Add Long Pairwise). */
> +void
> +bar3 (unsigned long long *__restrict b, unsigned long long *__restrict d)
> +{
> +  for (int i = 0; i < 1024; i++)
> +    d[i] = __builtin_popcountll (b[i]);
> +}
> +
> +/* This function should produce cnt v.8b and uaddlp (Add Long Pairwise). */
> +void
> +bar4 (unsigned short *__restrict b, unsigned short *__restrict d)
> +{
> +  for (int i = 0; i < 1028; i++)
> +    d[i] = __builtin_popcount (b[i]);
> +}
> +
> +/* This function should produce cnt v.8b and 2 uaddlp (Add Long Pairwise). */
> +void
> +bar5 (unsigned int *__restrict b, unsigned int *__restrict d)
> +{
> +  for (int i = 0; i < 1026; i++)
> +    d[i] = __builtin_popcount (b[i]);
> +}

It'd probably be safer to use an SLP test for bar4 and bar5, to ensure
that we continue to generate only a single popcount for this function.
In future, even -O2 might use 128-bit vectors for the main loop,
followed by a 64-bit vector epilogue for the remaining elements.
That would then give more 128-bit vector popcounts than the test
is expecting.

Thanks,
Richard

> +
> +/* SLP
> + This function should produce cnt v.16b and 3 uaddlp (Add Long Pairwise). */
> +void
> +bar6 (unsigned long long *__restrict b, unsigned long long *__restrict d)
> +{
> +  d[0] = __builtin_popcountll (b[0]);
> +  d[1] = __builtin_popcountll (b[1]);
> +}
> +
> +/* { dg-final { scan-assembler-not {\tbl\tpopcount} } } */
> +/* { dg-final { scan-assembler-times {cnt\t} 7 } } */
> +/* { dg-final { scan-assembler-times {uaddlp\t} 12 } } */
> +/* { dg-final { scan-assembler-times {ldr\tq} 5 } } */
> +/* { dg-final { scan-assembler-times {ldr\td} 2 } } */

RE: [PATCH v2] aarch64: Add vector popcount besides QImode [PR113859]

[Pengxuan Zheng (QUIC)]

> Pengxuan Zheng <quic_pzheng@quicinc.com> writes:
> > This patch improves GCC’s vectorization of __builtin_popcount for
> > aarch64 target by adding popcount patterns for vector modes besides
> > QImode, i.e., HImode, SImode and DImode.
> >
> > With this patch, we now generate the following for V8HI:
> >   cnt     v1.16b, v.16b
> >   uaddlp  v2.8h, v1.16b
> >
> > For V4HI, we generate:
> >   cnt     v1.8b, v.8b
> >   uaddlp  v2.4h, v1.8b
> >
> > For V4SI, we generate:
> >   cnt     v1.16b, v.16b
> >   uaddlp  v2.8h, v1.16b
> >   uaddlp  v3.4s, v2.8h
> >
> > For V2SI, we generate:
> >   cnt     v1.8b, v.8b
> >   uaddlp  v2.4h, v1.8b
> >   uaddlp  v3.2s, v2.4h
> >
> > For V2DI, we generate:
> >   cnt     v1.16b, v.16b
> >   uaddlp  v2.8h, v1.16b
> >   uaddlp  v3.4s, v2.8h
> >   uaddlp  v4.2d, v3.4s
> >
> > 	PR target/113859
> >
> > gcc/ChangeLog:
> >
> > 	* config/aarch64/aarch64-simd.md (aarch64_<su>addlp<mode>):
> Rename to...
> > 	(@aarch64_<su>addlp<mode>): ... This.
> > 	(popcount<mode>2): New define_expand.
> >
> > gcc/testsuite/ChangeLog:
> >
> > 	* gcc.target/aarch64/popcnt-vec.c: New test.
> > ---
> >  gcc/config/aarch64/aarch64-simd.md            | 28 +++++++-
> >  gcc/testsuite/gcc.target/aarch64/popcnt-vec.c | 65
> > +++++++++++++++++++
> >  2 files changed, 92 insertions(+), 1 deletion(-)  create mode 100644
> > gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
> >
> > diff --git a/gcc/config/aarch64/aarch64-simd.md
> > b/gcc/config/aarch64/aarch64-simd.md
> > index 0bb39091a38..38dba285f69 100644
> > --- a/gcc/config/aarch64/aarch64-simd.md
> > +++ b/gcc/config/aarch64/aarch64-simd.md
> > @@ -3461,7 +3461,7 @@ (define_insn
> "*aarch64_<su>addlv<VDQV_L:mode>_ze<GPI:mode>"
> >    [(set_attr "type" "neon_reduc_add<VDQV_L:q>")]
> >  )
> >
> > -(define_expand "aarch64_<su>addlp<mode>"
> > +(define_expand "@aarch64_<su>addlp<mode>"
> >    [(set (match_operand:<VDBLW> 0 "register_operand")
> >  	(plus:<VDBLW>
> >  	  (vec_select:<VDBLW>
> > @@ -3517,6 +3517,32 @@ (define_insn
> "popcount<mode>2<vczle><vczbe>"
> >    [(set_attr "type" "neon_cnt<q>")]
> >  )
> >
> > +(define_expand "popcount<mode>2"
> > +  [(set (match_operand:VDQHSD 0 "register_operand")
> > +        (popcount:VDQHSD (match_operand:VDQHSD 1
> > +"register_operand")))]
> > +  "TARGET_SIMD"
> > +  {
> > +    /* Generate a byte popcount. */
> > +    machine_mode mode = <bitsize> == 64 ? V8QImode : V16QImode;
> > +    rtx tmp = gen_reg_rtx (mode);
> > +    auto icode = optab_handler (popcount_optab, mode);
> > +    emit_insn (GEN_FCN (icode) (tmp, gen_lowpart (mode,
> > +operands[1])));
> > +
> > +    /* Use a sequence of UADDLPs to accumulate the counts. Each step
> doubles the
> > +       element size and halves the number of elements. */
> 
> Nit: reflowing this paragraph has made the first line too long.
> I think we should stick with the version in the review:
> 
>    /* Use a sequence of UADDLPs to accumulate the counts.  Each step
> doubles
>       the element size and halves the number of elements.  */

Good catch. I've fixed this in the latest version.
https://gcc.gnu.org/pipermail/gcc-patches/2024-June/654601.html

> 
> > +    do
> > +      {
> > +        auto icode = code_for_aarch64_addlp (ZERO_EXTEND, GET_MODE
> (tmp));
> > +        mode = insn_data[icode].operand[0].mode;
> > +        rtx dest = mode == <MODE>mode ? operands[0] : gen_reg_rtx
> (mode);
> > +        emit_insn (GEN_FCN (icode) (dest, tmp));
> > +        tmp = dest;
> > +      }
> > +    while (mode != <MODE>mode);
> > +    DONE;
> > +  }
> > +)
> > +
> >  ;; 'across lanes' max and min ops.
> >
> >  ;; Template for outputting a scalar, so we can create __builtins
> > which can be diff --git
> > a/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
> > b/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
> > new file mode 100644
> > index 00000000000..89860940296
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/popcnt-vec.c
> > @@ -0,0 +1,65 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +
> > +/* This function should produce cnt v.16b. */ void bar (unsigned char
> > +*__restrict b, unsigned char *__restrict d) {
> > +  for (int i = 0; i < 1024; i++)
> > +    d[i] = __builtin_popcount (b[i]); }
> > +
> > +/* This function should produce cnt v.16b and uaddlp (Add Long
> > +Pairwise). */ void
> > +bar1 (unsigned short *__restrict b, unsigned short *__restrict d) {
> > +  for (int i = 0; i < 1024; i++)
> > +    d[i] = __builtin_popcount (b[i]); }
> > +
> > +/* This function should produce cnt v.16b and 2 uaddlp (Add Long
> > +Pairwise). */ void
> > +bar2 (unsigned int *__restrict b, unsigned int *__restrict d) {
> > +  for (int i = 0; i < 1024; i++)
> > +    d[i] = __builtin_popcount (b[i]); }
> > +
> > +/* This function should produce cnt v.16b and 3 uaddlp (Add Long
> > +Pairwise). */ void
> > +bar3 (unsigned long long *__restrict b, unsigned long long
> > +*__restrict d) {
> > +  for (int i = 0; i < 1024; i++)
> > +    d[i] = __builtin_popcountll (b[i]); }
> > +
> > +/* This function should produce cnt v.8b and uaddlp (Add Long
> > +Pairwise). */ void
> > +bar4 (unsigned short *__restrict b, unsigned short *__restrict d) {
> > +  for (int i = 0; i < 1028; i++)
> > +    d[i] = __builtin_popcount (b[i]); }
> > +
> > +/* This function should produce cnt v.8b and 2 uaddlp (Add Long
> > +Pairwise). */ void
> > +bar5 (unsigned int *__restrict b, unsigned int *__restrict d) {
> > +  for (int i = 0; i < 1026; i++)
> > +    d[i] = __builtin_popcount (b[i]); }
> 
> It'd probably be safer to use an SLP test for bar4 and bar5, to ensure that we
> continue to generate only a single popcount for this function.
> In future, even -O2 might use 128-bit vectors for the main loop, followed by a
> 64-bit vector epilogue for the remaining elements.
> That would then give more 128-bit vector popcounts than the test is
> expecting.

That makes sense. I've updated the tests accordingly. However, there seems to be
some issue with the cost model which causes SLP to fail to vectorize bar5.
Therefore, I added -fno-vect-cost-model to work around the issue. Please let me
know if we should do this differently.

https://gcc.gnu.org/pipermail/gcc-patches/2024-June/654601.html

Thanks,
Pengxuan
> 
> Thanks,
> Richard
> 
> > +
> > +/* SLP
> > + This function should produce cnt v.16b and 3 uaddlp (Add Long
> > +Pairwise). */ void
> > +bar6 (unsigned long long *__restrict b, unsigned long long
> > +*__restrict d) {
> > +  d[0] = __builtin_popcountll (b[0]);
> > +  d[1] = __builtin_popcountll (b[1]); }
> > +
> > +/* { dg-final { scan-assembler-not {\tbl\tpopcount} } } */
> > +/* { dg-final { scan-assembler-times {cnt\t} 7 } } */
> > +/* { dg-final { scan-assembler-times {uaddlp\t} 12 } } */
> > +/* { dg-final { scan-assembler-times {ldr\tq} 5 } } */
> > +/* { dg-final { scan-assembler-times {ldr\td} 2 } } */