AArch64: Remove AARCH64_EXTRA_TUNE_USE_NEW_VECTOR_COSTS

AArch64: Remove AARCH64_EXTRA_TUNE_USE_NEW_VECTOR_COSTS

This patch removes the AARCH64_EXTRA_TUNE_USE_NEW_VECTOR_COSTS tunable and
use_new_vector_costs entry in aarch64-tuning-flags.def and makes the
AARCH64_EXTRA_TUNE_USE_NEW_VECTOR_COSTS paths in the backend the
default. To that end, the function aarch64_use_new_vector_costs_p and its uses
were removed. To prevent costing vec_to_scalar operations with 0, as
described in
https://gcc.gnu.org/pipermail/gcc-patches/2024-October/665481.html,
we adjusted vectorizable_store such that the variable n_adjacent_stores
also covers vec_to_scalar operations. This way vec_to_scalar operations
are not costed individually, but as a group.
As suggested by Richard Sandiford, the "known_ne" in the multilane-check
was replaced by "maybe_ne" in order to treat nunits==1+1X as a vector
rather than a scalar.

Two tests were adjusted due to changes in codegen. In both cases, the
old code performed loop unrolling once, but the new code does not:
Example from gcc.target/aarch64/sve/strided_load_2.c (compiled with
-O2 -ftree-vectorize -march=armv8.2-a+sve -mtune=generic -moverride=tune=none):
f_int64_t_32:
        cbz     w3, .L92
        mov     x4, 0
        uxtw    x3, w3
+       cntd    x5
+       whilelo p7.d, xzr, x3
+       mov     z29.s, w5
        mov     z31.s, w2
-       whilelo p6.d, xzr, x3
-       mov     x2, x3
-       index   z30.s, #0, #1
-       uqdecd  x2
-       ptrue   p5.b, all
-       whilelo p7.d, xzr, x2
+       index   z30.d, #0, #1
+       ptrue   p6.b, all
        .p2align 3,,7
 .L94:
-       ld1d    z27.d, p7/z, [x0, #1, mul vl]
-       ld1d    z28.d, p6/z, [x0]
-       movprfx z29, z31
-       mul     z29.s, p5/m, z29.s, z30.s
-       incw    x4
-       uunpklo z0.d, z29.s
-       uunpkhi z29.d, z29.s
-       ld1d    z25.d, p6/z, [x1, z0.d, lsl 3]
-       ld1d    z26.d, p7/z, [x1, z29.d, lsl 3]
-       add     z25.d, z28.d, z25.d
+       ld1d    z27.d, p7/z, [x0, x4, lsl 3]
+       movprfx z28, z31
+       mul     z28.s, p6/m, z28.s, z30.s
+       ld1d    z26.d, p7/z, [x1, z28.d, uxtw 3]
        add     z26.d, z27.d, z26.d
-       st1d    z26.d, p7, [x0, #1, mul vl]
-       whilelo p7.d, x4, x2
-       st1d    z25.d, p6, [x0]
-       incw    z30.s
-       incb    x0, all, mul #2
-       whilelo p6.d, x4, x3
+       st1d    z26.d, p7, [x0, x4, lsl 3]
+       add     z30.s, z30.s, z29.s
+       incd    x4
+       whilelo p7.d, x4, x3
        b.any   .L94
 .L92:
        ret

Example from gcc.target/aarch64/sve/strided_store_2.c (compiled with
-O2 -ftree-vectorize -march=armv8.2-a+sve -mtune=generic -moverride=tune=none):
f_int64_t_32:
        cbz     w3, .L84
-       addvl   x5, x1, #1
        mov     x4, 0
        uxtw    x3, w3
-       mov     z31.s, w2
+       cntd    x5
        whilelo p7.d, xzr, x3
-       mov     x2, x3
-       index   z30.s, #0, #1
-       uqdecd  x2
-       ptrue   p5.b, all
-       whilelo p6.d, xzr, x2
+       mov     z29.s, w5
+       mov     z31.s, w2
+       index   z30.d, #0, #1
+       ptrue   p6.b, all
        .p2align 3,,7
 .L86:
-       ld1d    z28.d, p7/z, [x1, x4, lsl 3]
-       ld1d    z27.d, p6/z, [x5, x4, lsl 3]
-       movprfx z29, z30
-       mul     z29.s, p5/m, z29.s, z31.s
-       add     z28.d, z28.d, #1
-       uunpklo z26.d, z29.s
-       st1d    z28.d, p7, [x0, z26.d, lsl 3]
-       incw    x4
-       uunpkhi z29.d, z29.s
+       ld1d    z27.d, p7/z, [x1, x4, lsl 3]
+       movprfx z28, z30
+       mul     z28.s, p6/m, z28.s, z31.s
        add     z27.d, z27.d, #1
-       whilelo p6.d, x4, x2
-       st1d    z27.d, p7, [x0, z29.d, lsl 3]
-       incw    z30.s
+       st1d    z27.d, p7, [x0, z28.d, uxtw 3]
+       incd    x4
+       add     z30.s, z30.s, z29.s
        whilelo p7.d, x4, x3
        b.any   .L86
 .L84:
	ret

The patch was bootstrapped and tested on aarch64-linux-gnu, no
regression.
OK for mainline?

Signed-off-by: Jennifer Schmitz <jschmitz@nvidia.com>
gcc/
	* tree-vect-stmts.cc (vectorizable_store): Extend the use of
	n_adjacent_stores to also cover vec_to_scalar operations.
	* config/aarch64/aarch64-tuning-flags.def: Remove
	use_new_vector_costs as tuning option.
	* config/aarch64/aarch64.cc (aarch64_use_new_vector_costs_p):
	Remove.
	(aarch64_vector_costs::add_stmt_cost): Remove use of
	aarch64_use_new_vector_costs_p.
	(aarch64_vector_costs::finish_cost): Remove use of
	aarch64_use_new_vector_costs_p.
	* config/aarch64/tuning_models/cortexx925.h: Remove
	AARCH64_EXTRA_TUNE_USE_NEW_VECTOR_COSTS.
	* config/aarch64/tuning_models/fujitsu_monaka.h: Likewise.
	* config/aarch64/tuning_models/generic_armv8_a.h: Likewise.
	* config/aarch64/tuning_models/generic_armv9_a.h: Likewise.
	* config/aarch64/tuning_models/neoverse512tvb.h: Likewise.
	* config/aarch64/tuning_models/neoversen2.h: Likewise.
	* config/aarch64/tuning_models/neoversen3.h: Likewise.
	* config/aarch64/tuning_models/neoversev1.h: Likewise.
	* config/aarch64/tuning_models/neoversev2.h: Likewise.
	* config/aarch64/tuning_models/neoversev3.h: Likewise.
	* config/aarch64/tuning_models/neoversev3ae.h: Likewise.

gcc/testsuite/
	* gcc.target/aarch64/sve/strided_load_2.c: Adjust expected outcome.
	* gcc.target/aarch64/sve/strided_store_2.c: Likewise.