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* [gcc r13-6620] AArch64: Update div-bitmask to implement new optab instead of target hook [PR108583]
@ 2023-03-12 18:44 Tamar Christina
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From: Tamar Christina @ 2023-03-12 18:44 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:f23dc726875c26f2c38dfded453aa9beba0b9be9
commit r13-6620-gf23dc726875c26f2c38dfded453aa9beba0b9be9
Author: Tamar Christina <tamar.christina@arm.com>
Date: Sun Mar 12 18:42:59 2023 +0000
AArch64: Update div-bitmask to implement new optab instead of target hook [PR108583]
This replaces the custom division hook with just an implementation through
add_highpart. For NEON we implement the add highpart (Addition + extraction of
the upper highpart of the register in the same precision) as ADD + LSR.
This representation allows us to easily optimize the sequence using existing
sequences. This gets us a pretty decent sequence using SRA:
umull v1.8h, v0.8b, v3.8b
umull2 v0.8h, v0.16b, v3.16b
add v5.8h, v1.8h, v2.8h
add v4.8h, v0.8h, v2.8h
usra v1.8h, v5.8h, 8
usra v0.8h, v4.8h, 8
uzp2 v1.16b, v1.16b, v0.16b
To get the most optimal sequence however we match (a + ((b + c) >> n)) where n
is half the precision of the mode of the operation into addhn + uaddw which is
a general good optimization on its own and gets us back to:
.L4:
ldr q0, [x3]
umull v1.8h, v0.8b, v5.8b
umull2 v0.8h, v0.16b, v5.16b
addhn v3.8b, v1.8h, v4.8h
addhn v2.8b, v0.8h, v4.8h
uaddw v1.8h, v1.8h, v3.8b
uaddw v0.8h, v0.8h, v2.8b
uzp2 v1.16b, v1.16b, v0.16b
str q1, [x3], 16
cmp x3, x4
bne .L4
For SVE2 we optimize the initial sequence to the same ADD + LSR which gets us:
.L3:
ld1b z0.h, p0/z, [x0, x3]
mul z0.h, p1/m, z0.h, z2.h
add z1.h, z0.h, z3.h
usra z0.h, z1.h, #8
lsr z0.h, z0.h, #8
st1b z0.h, p0, [x0, x3]
inch x3
whilelo p0.h, w3, w2
b.any .L3
.L1:
ret
and to get the most optimal sequence I match (a + b) >> n (same constraint on n)
to addhnb which gets us to:
.L3:
ld1b z0.h, p0/z, [x0, x3]
mul z0.h, p1/m, z0.h, z2.h
addhnb z1.b, z0.h, z3.h
addhnb z0.b, z0.h, z1.h
st1b z0.h, p0, [x0, x3]
inch x3
whilelo p0.h, w3, w2
b.any .L3
There are multiple RTL representations possible for these optimizations, I did
not represent them using a zero_extend because we seem very inconsistent in this
in the backend. Since they are unspecs we won't match them from vector ops
anyway. I figured maintainers would prefer this, but my maintainer ouija board
is still out for repairs :)
There are no new test as new correctness tests were added to the mid-end and
the existing codegen tests for this already exist.
gcc/ChangeLog:
PR target/108583
* config/aarch64/aarch64-simd.md (@aarch64_bitmask_udiv<mode>3): Remove.
(*bitmask_shift_plus<mode>): New.
* config/aarch64/aarch64-sve2.md (*bitmask_shift_plus<mode>): New.
(@aarch64_bitmask_udiv<mode>3): Remove.
* config/aarch64/aarch64.cc
(aarch64_vectorize_can_special_div_by_constant,
TARGET_VECTORIZE_CAN_SPECIAL_DIV_BY_CONST): Removed.
(TARGET_VECTORIZE_PREFERRED_DIV_AS_SHIFTS_OVER_MULT,
aarch64_vectorize_preferred_div_as_shifts_over_mult): New.
Diff:
---
gcc/config/aarch64/aarch64-simd.md | 71 ++++++++++----------------------------
gcc/config/aarch64/aarch64-sve2.md | 57 +++++++++---------------------
gcc/config/aarch64/aarch64.cc | 61 +++++++++-----------------------
3 files changed, 52 insertions(+), 137 deletions(-)
diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
index 772dd7693b3..b63c1fe1543 100644
--- a/gcc/config/aarch64/aarch64-simd.md
+++ b/gcc/config/aarch64/aarch64-simd.md
@@ -4867,60 +4867,27 @@
}
)
-;; div optimizations using narrowings
-;; we can do the division e.g. shorts by 255 faster by calculating it as
-;; (x + ((x + 257) >> 8)) >> 8 assuming the operation is done in
-;; double the precision of x.
-;;
-;; If we imagine a short as being composed of two blocks of bytes then
-;; adding 257 or 0b0000_0001_0000_0001 to the number is equivalent to
-;; adding 1 to each sub component:
-;;
-;; short value of 16-bits
-;; ┌──────────────┬────────────────┐
-;; │ │ │
-;; └──────────────┴────────────────┘
-;; 8-bit part1 ▲ 8-bit part2 ▲
-;; │ │
-;; │ │
-;; +1 +1
-;;
-;; after the first addition, we have to shift right by 8, and narrow the
-;; results back to a byte. Remember that the addition must be done in
-;; double the precision of the input. Since 8 is half the size of a short
-;; we can use a narrowing halfing instruction in AArch64, addhn which also
-;; does the addition in a wider precision and narrows back to a byte. The
-;; shift itself is implicit in the operation as it writes back only the top
-;; half of the result. i.e. bits 2*esize-1:esize.
-;;
-;; Since we have narrowed the result of the first part back to a byte, for
-;; the second addition we can use a widening addition, uaddw.
-;;
-;; For the final shift, since it's unsigned arithmetic we emit an ushr by 8.
-;;
-;; The shift is later optimized by combine to a uzp2 with movi #0.
-(define_expand "@aarch64_bitmask_udiv<mode>3"
- [(match_operand:VQN 0 "register_operand")
- (match_operand:VQN 1 "register_operand")
- (match_operand:VQN 2 "immediate_operand")]
+;; Optimize ((a + b) >> n) + c where n is half the bitsize of the vector
+(define_insn_and_split "*bitmask_shift_plus<mode>"
+ [(set (match_operand:VQN 0 "register_operand" "=&w")
+ (plus:VQN
+ (lshiftrt:VQN
+ (plus:VQN (match_operand:VQN 1 "register_operand" "w")
+ (match_operand:VQN 2 "register_operand" "w"))
+ (match_operand:VQN 3 "aarch64_simd_shift_imm_vec_exact_top" ""))
+ (match_operand:VQN 4 "register_operand" "w")))]
"TARGET_SIMD"
+ "#"
+ "&& true"
+ [(const_int 0)]
{
- unsigned HOST_WIDE_INT size
- = (1ULL << GET_MODE_UNIT_BITSIZE (<VNARROWQ>mode)) - 1;
- rtx elt = unwrap_const_vec_duplicate (operands[2]);
- if (!CONST_INT_P (elt) || UINTVAL (elt) != size)
- FAIL;
-
- rtx addend = gen_reg_rtx (<MODE>mode);
- rtx val = aarch64_simd_gen_const_vector_dup (<VNARROWQ2>mode, 1);
- emit_move_insn (addend, lowpart_subreg (<MODE>mode, val, <VNARROWQ2>mode));
- rtx tmp1 = gen_reg_rtx (<VNARROWQ>mode);
- rtx tmp2 = gen_reg_rtx (<MODE>mode);
- emit_insn (gen_aarch64_addhn<mode> (tmp1, operands[1], addend));
- unsigned bitsize = GET_MODE_UNIT_BITSIZE (<VNARROWQ>mode);
- rtx shift_vector = aarch64_simd_gen_const_vector_dup (<MODE>mode, bitsize);
- emit_insn (gen_aarch64_uaddw<Vnarrowq> (tmp2, operands[1], tmp1));
- emit_insn (gen_aarch64_simd_lshr<mode> (operands[0], tmp2, shift_vector));
+ rtx tmp;
+ if (can_create_pseudo_p ())
+ tmp = gen_reg_rtx (<VNARROWQ>mode);
+ else
+ tmp = gen_rtx_REG (<VNARROWQ>mode, REGNO (operands[0]));
+ emit_insn (gen_aarch64_addhn<mode> (tmp, operands[1], operands[2]));
+ emit_insn (gen_aarch64_uaddw<Vnarrowq> (operands[0], operands[4], tmp));
DONE;
})
diff --git a/gcc/config/aarch64/aarch64-sve2.md b/gcc/config/aarch64/aarch64-sve2.md
index 40c0728a7e6..2346f9f835d 100644
--- a/gcc/config/aarch64/aarch64-sve2.md
+++ b/gcc/config/aarch64/aarch64-sve2.md
@@ -71,7 +71,6 @@
;; ---- [INT] Reciprocal approximation
;; ---- [INT<-FP] Base-2 logarithm
;; ---- [INT] Polynomial multiplication
-;; ---- [INT] Misc optab implementations
;;
;; == Permutation
;; ---- [INT,FP] General permutes
@@ -1600,6 +1599,22 @@
"<sve_int_op>\t%0.<Ventype>, %2.<Vetype>, %3.<Vetype>"
)
+;; Optimize ((a + b) >> n) where n is half the bitsize of the vector
+(define_insn "*bitmask_shift_plus<mode>"
+ [(set (match_operand:SVE_FULL_HSDI 0 "register_operand" "=w")
+ (unspec:SVE_FULL_HSDI
+ [(match_operand:<VPRED> 1)
+ (lshiftrt:SVE_FULL_HSDI
+ (plus:SVE_FULL_HSDI
+ (match_operand:SVE_FULL_HSDI 2 "register_operand" "w")
+ (match_operand:SVE_FULL_HSDI 3 "register_operand" "w"))
+ (match_operand:SVE_FULL_HSDI 4
+ "aarch64_simd_shift_imm_vec_exact_top" ""))]
+ UNSPEC_PRED_X))]
+ "TARGET_SVE2"
+ "addhnb\t%0.<Ventype>, %2.<Vetype>, %3.<Vetype>"
+)
+
;; -------------------------------------------------------------------------
;; ---- [INT] Narrowing right shifts
;; -------------------------------------------------------------------------
@@ -2313,46 +2328,6 @@
"<sve_int_op>\t%0.<Vewtype>, %1.<Vetype>, %2.<Vetype>"
)
-;; -------------------------------------------------------------------------
-;; ---- [INT] Misc optab implementations
-;; -------------------------------------------------------------------------
-;; Includes:
-;; - aarch64_bitmask_udiv
-;; -------------------------------------------------------------------------
-
-;; div optimizations using narrowings
-;; we can do the division e.g. shorts by 255 faster by calculating it as
-;; (x + ((x + 257) >> 8)) >> 8 assuming the operation is done in
-;; double the precision of x.
-;;
-;; See aarch64-simd.md for bigger explanation.
-(define_expand "@aarch64_bitmask_udiv<mode>3"
- [(match_operand:SVE_FULL_HSDI 0 "register_operand")
- (match_operand:SVE_FULL_HSDI 1 "register_operand")
- (match_operand:SVE_FULL_HSDI 2 "immediate_operand")]
- "TARGET_SVE2"
-{
- unsigned HOST_WIDE_INT size
- = (1ULL << GET_MODE_UNIT_BITSIZE (<VNARROW>mode)) - 1;
- rtx elt = unwrap_const_vec_duplicate (operands[2]);
- if (!CONST_INT_P (elt) || UINTVAL (elt) != size)
- FAIL;
-
- rtx addend = gen_reg_rtx (<MODE>mode);
- rtx tmp1 = gen_reg_rtx (<VNARROW>mode);
- rtx tmp2 = gen_reg_rtx (<VNARROW>mode);
- rtx val = aarch64_simd_gen_const_vector_dup (<VNARROW>mode, 1);
- emit_move_insn (addend, lowpart_subreg (<MODE>mode, val, <VNARROW>mode));
- emit_insn (gen_aarch64_sve (UNSPEC_ADDHNB, <MODE>mode, tmp1, operands[1],
- addend));
- emit_insn (gen_aarch64_sve (UNSPEC_ADDHNB, <MODE>mode, tmp2, operands[1],
- lowpart_subreg (<MODE>mode, tmp1,
- <VNARROW>mode)));
- emit_move_insn (operands[0],
- lowpart_subreg (<MODE>mode, tmp2, <VNARROW>mode));
- DONE;
-})
-
;; =========================================================================
;; == Permutation
;; =========================================================================
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 5c40b6ed22a..8a06879e94f 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -3847,6 +3847,19 @@ aarch64_vectorize_related_mode (machine_mode vector_mode,
return default_vectorize_related_mode (vector_mode, element_mode, nunits);
}
+/* Implement TARGET_VECTORIZE_PREFERRED_DIV_AS_SHIFTS_OVER_MULT. */
+
+static bool
+aarch64_vectorize_preferred_div_as_shifts_over_mult (const_tree type)
+{
+ machine_mode mode = TYPE_MODE (type);
+ unsigned int vec_flags = aarch64_classify_vector_mode (mode);
+ bool sve_p = (vec_flags & VEC_ANY_SVE);
+ bool simd_p = (vec_flags & VEC_ADVSIMD);
+
+ return (sve_p && TARGET_SVE2) || (simd_p && TARGET_SIMD);
+}
+
/* Implement TARGET_PREFERRED_ELSE_VALUE. For binary operations,
prefer to use the first arithmetic operand as the else value if
the else value doesn't matter, since that exactly matches the SVE
@@ -24361,46 +24374,6 @@ aarch64_vectorize_vec_perm_const (machine_mode vmode, machine_mode op_mode,
return ret;
}
-
-/* Implement TARGET_VECTORIZE_CAN_SPECIAL_DIV_BY_CONST. */
-
-bool
-aarch64_vectorize_can_special_div_by_constant (enum tree_code code,
- tree vectype, wide_int cst,
- rtx *output, rtx in0, rtx in1)
-{
- if (code != TRUNC_DIV_EXPR
- || !TYPE_UNSIGNED (vectype))
- return false;
-
- machine_mode mode = TYPE_MODE (vectype);
- unsigned int flags = aarch64_classify_vector_mode (mode);
- if ((flags & VEC_ANY_SVE) && !TARGET_SVE2)
- return false;
-
- int pow = wi::exact_log2 (cst + 1);
- auto insn_code = maybe_code_for_aarch64_bitmask_udiv3 (TYPE_MODE (vectype));
- /* SVE actually has a div operator, we may have gotten here through
- that route. */
- if (pow != (int) (element_precision (vectype) / 2)
- || insn_code == CODE_FOR_nothing)
- return false;
-
- /* We can use the optimized pattern. */
- if (in0 == NULL_RTX && in1 == NULL_RTX)
- return true;
-
- gcc_assert (output);
-
- expand_operand ops[3];
- create_output_operand (&ops[0], *output, mode);
- create_input_operand (&ops[1], in0, mode);
- create_fixed_operand (&ops[2], in1);
- expand_insn (insn_code, 3, ops);
- *output = ops[0].value;
- return true;
-}
-
/* Generate a byte permute mask for a register of mode MODE,
which has NUNITS units. */
@@ -27902,13 +27875,13 @@ aarch64_libgcc_floating_mode_supported_p
#undef TARGET_MAX_ANCHOR_OFFSET
#define TARGET_MAX_ANCHOR_OFFSET 4095
+#undef TARGET_VECTORIZE_PREFERRED_DIV_AS_SHIFTS_OVER_MULT
+#define TARGET_VECTORIZE_PREFERRED_DIV_AS_SHIFTS_OVER_MULT \
+ aarch64_vectorize_preferred_div_as_shifts_over_mult
+
#undef TARGET_VECTOR_ALIGNMENT
#define TARGET_VECTOR_ALIGNMENT aarch64_simd_vector_alignment
-#undef TARGET_VECTORIZE_CAN_SPECIAL_DIV_BY_CONST
-#define TARGET_VECTORIZE_CAN_SPECIAL_DIV_BY_CONST \
- aarch64_vectorize_can_special_div_by_constant
-
#undef TARGET_VECTORIZE_PREFERRED_VECTOR_ALIGNMENT
#define TARGET_VECTORIZE_PREFERRED_VECTOR_ALIGNMENT \
aarch64_vectorize_preferred_vector_alignment
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