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Re: [PATCH 1/2] [ARM] PR68532: Fix up vuzp for big endian

From: Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>
To: charles dot baylis at linaro dot org, Ramana dot Radhakrishnan at arm dot com, richard dot earnshaw at arm dot com
Cc: rearnsha at arm dot com, gcc-patches at gcc dot gnu dot org, michael dot collison at linaro dot org
Date: Mon, 08 Feb 2016 11:42:21 +0000
Subject: Re: [PATCH 1/2] [ARM] PR68532: Fix up vuzp for big endian
Authentication-results: sourceware.org; auth=none
References: <1454525947-14690-1-git-send-email-charles dot baylis at linaro dot org> <1454525947-14690-2-git-send-email-charles dot baylis at linaro dot org>

Hi Charles,

On 03/02/16 18:59, charles.baylis@linaro.org wrote:

From: Charles Baylis <charles.baylis@linaro.org>

gcc/ChangeLog:

2016-02-03  Charles Baylis  <charles.baylis@linaro.org>

	PR target/68532
	* config/arm/arm.c (neon_endian_lane_map): New function.
	(neon_vector_pair_endian_lane_map): New function.
	(arm_evpc_neon_vuzp): Allow for big endian lane order.
	* config/arm/arm_neon.h (vuzpq_s8): Adjust shuffle patterns for big
	endian.
	(vuzpq_s16): Likewise.
	(vuzpq_s32): Likewise.
	(vuzpq_f32): Likewise.
	(vuzpq_u8): Likewise.
	(vuzpq_u16): Likewise.
	(vuzpq_u32): Likewise.
	(vuzpq_p8): Likewise.
	(vuzpq_p16): Likewise.

gcc/testsuite/ChangeLog:

2015-12-15  Charles Baylis  <charles.baylis@linaro.org>

	PR target/68532
	* gcc.c-torture/execute/pr68532.c: New test.

Change-Id: Ifd35d79bd42825f05403a1b96d8f34ef0f21dac3

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index d8a2745..e9aa982 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -28208,6 +28208,35 @@ arm_expand_vec_perm (rtx target, rtx op0, rtx op1, rtx sel)
    arm_expand_vec_perm_1 (target, op0, op1, sel);
  }

+/* map lane ordering between architectural lane order, and GCC lane order,

+   taking into account ABI.  See comment above output_move_neon for details.  */
+static int
+neon_endian_lane_map (machine_mode mode, int lane)


s/map/Map/
New line between comment and function signature.

+{
+  if (BYTES_BIG_ENDIAN)
+  {
+    int nelems = GET_MODE_NUNITS (mode);
+    /* Reverse lane order.  */
+    lane = (nelems - 1 - lane);
+    /* Reverse D register order, to match ABI.  */
+    if (GET_MODE_SIZE (mode) == 16)
+      lane = lane ^ (nelems / 2);
+  }
+  return lane;
+}
+
+/* some permutations index into pairs of vectors, this is a helper function
+   to map indexes into those pairs of vectors.  */
+static int
+neon_pair_endian_lane_map (machine_mode mode, int lane)


Similarly, s/some/Some/ and new line after comment.

+{
+  int nelem = GET_MODE_NUNITS (mode);
+  if (BYTES_BIG_ENDIAN)
+    lane =
+      neon_endian_lane_map (mode, lane & (nelem - 1)) + (lane & nelem);
+  return lane;
+}
+
  /* Generate or test for an insn that supports a constant permutation.  */

/* Recognize patterns for the VUZP insns. */

@@ -28218,14 +28247,22 @@ arm_evpc_neon_vuzp (struct expand_vec_perm_d *d)
    unsigned int i, odd, mask, nelt = d->nelt;
    rtx out0, out1, in0, in1;
    rtx (*gen)(rtx, rtx, rtx, rtx);
+  int first_elem;
+  int swap;


Just make this a bool.

    if (GET_MODE_UNIT_SIZE (d->vmode) >= 8)
      return false;

- /* Note that these are little-endian tests. Adjust for big-endian later. */

-  if (d->perm[0] == 0)
+  /* arm_expand_vec_perm_const_1 () helpfully swaps the operands for the
+     big endian pattern on 64 bit vectors, so we correct for that.  */
+  swap = BYTES_BIG_ENDIAN && !d->one_vector_p
+    && GET_MODE_SIZE (d->vmode) == 8 ? d->nelt : 0;
+
+  first_elem = d->perm[neon_endian_lane_map (d->vmode, 0)] ^ swap;
+
+  if (first_elem == neon_endian_lane_map (d->vmode, 0))
      odd = 0;
-  else if (d->perm[0] == 1)
+  else if (first_elem == neon_endian_lane_map (d->vmode, 1))
      odd = 1;
    else
      return false;
@@ -28233,8 +28270,9 @@ arm_evpc_neon_vuzp (struct expand_vec_perm_d *d)

for (i = 0; i < nelt; i++)

      {
-      unsigned elt = (i * 2 + odd) & mask;
-      if (d->perm[i] != elt)
+      unsigned elt =
+	(neon_pair_endian_lane_map (d->vmode, i) * 2 + odd) & mask;
+      if ((d->perm[i] ^ swap) != neon_pair_endian_lane_map (d->vmode, elt))
  	return false;
      }

@@ -28258,10 +28296,9 @@ arm_evpc_neon_vuzp (struct expand_vec_perm_d *d)in0 = d->op0;

    in1 = d->op1;
-  if (BYTES_BIG_ENDIAN)
+  if (swap)
      {
        std::swap (in0, in1);
-      odd = !odd;
      }


remove the braces around the std::swap

out0 = d->target;

diff --git a/gcc/config/arm/arm_neon.h b/gcc/config/arm/arm_neon.h
index 47816d5..2e014b6 100644
--- a/gcc/config/arm/arm_neon.h
+++ b/gcc/config/arm/arm_neon.h
@@ -8741,9 +8741,9 @@ vuzpq_s8 (int8x16_t __a, int8x16_t __b)
    int8x16x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint8x16_t)
-      { 17, 19, 21, 23, 25, 27, 29, 31, 1, 3, 5, 7, 9, 11, 13, 15 });
+      { 9, 11, 13, 15, 1, 3, 5, 7, 25, 27, 29, 31, 17, 19, 21, 23 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint8x16_t)
-      { 16, 18, 20, 22, 24, 26, 28, 30, 0, 2, 4, 6, 8, 10, 12, 14 });
+      { 8, 10, 12, 14, 0, 2, 4, 6, 24, 26, 28, 30, 16, 18, 20, 22 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint8x16_t)
        { 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 });
@@ -8759,9 +8759,9 @@ vuzpq_s16 (int16x8_t __a, int16x8_t __b)
    int16x8x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint16x8_t)
-      { 9, 11, 13, 15, 1, 3, 5, 7 });
+      { 5, 7, 1, 3, 13, 15, 9, 11 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint16x8_t)
-      { 8, 10, 12, 14, 0, 2, 4, 6 });
+      { 4, 6, 0, 2, 12, 14, 8, 10 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint16x8_t)
        { 0, 2, 4, 6, 8, 10, 12, 14 });
@@ -8776,8 +8776,8 @@ vuzpq_s32 (int32x4_t __a, int32x4_t __b)
  {
    int32x4x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
-  __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 5, 7, 1, 3 });
-  __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 4, 6, 0, 2 });
+  __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 3, 1, 7, 5 });
+  __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 2, 0, 6, 4 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 0, 2, 4, 6 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 1, 3, 5, 7 });
@@ -8790,8 +8790,8 @@ vuzpq_f32 (float32x4_t __a, float32x4_t __b)
  {
    float32x4x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
-  __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 5, 7, 1, 3 });
-  __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 4, 6, 0, 2 });
+  __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 3, 1, 7, 5 });
+  __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 2, 0, 6, 4 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 0, 2, 4, 6 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 1, 3, 5, 7 });
@@ -8805,9 +8805,9 @@ vuzpq_u8 (uint8x16_t __a, uint8x16_t __b)
    uint8x16x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint8x16_t)
-      { 17, 19, 21, 23, 25, 27, 29, 31, 1, 3, 5, 7, 9, 11, 13, 15 });
+      { 9, 11, 13, 15, 1, 3, 5, 7, 25, 27, 29, 31, 17, 19, 21, 23 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint8x16_t)
-      { 16, 18, 20, 22, 24, 26, 28, 30, 0, 2, 4, 6, 8, 10, 12, 14 });
+      { 8, 10, 12, 14, 0, 2, 4, 6, 24, 26, 28, 30, 16, 18, 20, 22 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint8x16_t)
        { 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 });
@@ -8823,9 +8823,9 @@ vuzpq_u16 (uint16x8_t __a, uint16x8_t __b)
    uint16x8x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint16x8_t)
-      { 9, 11, 13, 15, 1, 3, 5, 7 });
+      { 5, 7, 1, 3, 13, 15, 9, 11 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint16x8_t)
-      { 8, 10, 12, 14, 0, 2, 4, 6 });
+      { 4, 6, 0, 2, 12, 14, 8, 10 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint16x8_t)
        { 0, 2, 4, 6, 8, 10, 12, 14 });
@@ -8840,8 +8840,8 @@ vuzpq_u32 (uint32x4_t __a, uint32x4_t __b)
  {
    uint32x4x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
-  __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 5, 7, 1, 3 });
-  __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 4, 6, 0, 2 });
+  __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 3, 1, 7, 5 });
+  __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 2, 0, 6, 4 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint32x4_t) { 0, 2, 4, 6 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint32x4_t) { 1, 3, 5, 7 });
@@ -8855,9 +8855,9 @@ vuzpq_p8 (poly8x16_t __a, poly8x16_t __b)
    poly8x16x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint8x16_t)
-      { 17, 19, 21, 23, 25, 27, 29, 31, 1, 3, 5, 7, 9, 11, 13, 15 });
+      { 9, 11, 13, 15, 1, 3, 5, 7, 25, 27, 29, 31, 17, 19, 21, 23 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint8x16_t)
-      { 16, 18, 20, 22, 24, 26, 28, 30, 0, 2, 4, 6, 8, 10, 12, 14 });
+      { 8, 10, 12, 14, 0, 2, 4, 6, 24, 26, 28, 30, 16, 18, 20, 22 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint8x16_t)
        { 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 });
@@ -8873,9 +8873,9 @@ vuzpq_p16 (poly16x8_t __a, poly16x8_t __b)
    poly16x8x2_t __rv;
  #ifdef __ARM_BIG_ENDIAN
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint16x8_t)
-      { 9, 11, 13, 15, 1, 3, 5, 7 });
+      { 5, 7, 1, 3, 13, 15, 9, 11 });
    __rv.val[1] = __builtin_shuffle (__a, __b, (uint16x8_t)
-      { 8, 10, 12, 14, 0, 2, 4, 6 });
+      { 4, 6, 0, 2, 12, 14, 8, 10 });
  #else
    __rv.val[0] = __builtin_shuffle (__a, __b, (uint16x8_t)
        { 0, 2, 4, 6, 8, 10, 12, 14 });
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr68532.c b/gcc/testsuite/gcc.c-torture/execute/pr68532.c
new file mode 100644
index 0000000..3c40aa8
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr68532.c
@@ -0,0 +1,24 @@
+/* { dg-options "-O2 -ftree-vectorize -fno-vect-cost-model" } */
+
+#define SIZE 128
+unsigned short _Alignas (16) in[SIZE];
+
+extern void abort (void);
+
+__attribute__ ((noinline)) int
+test (unsigned short sum, unsigned short *in, int x)
+{
+  for (int j = 0; j < SIZE; j += 8)
+    sum += in[j] * x;
+  return sum;
+}
+
+int
+main ()
+{
+  for (int i = 0; i < SIZE; i++)
+    in[i] = i;
+  if (test (0, in, 1) != 960)
+    abort ();


AFAIK tests here usually prefer __builtin_abort ();
That way you don't have to declare the abort prototype in the beginning.

Ok with those changes.

Thanks,
Kyrill

Follow-Ups:
- Re: [PATCH 1/2] [ARM] PR68532: Fix up vuzp for big endian
  - From: Charles Baylis

References:
- [ARM, PATCH v2 0/2] PR68532: Fix VZIP/VUZP recognition for big endian
  - From: charles . baylis
- [PATCH 1/2] [ARM] PR68532: Fix up vuzp for big endian
  - From: charles . baylis

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