From: James Greenhalgh Date: Thu, 17 May 2018 09:39:02 +0000 (+0000) Subject: [patch AArch64] Do not perform a vector splat for vector initialisation if it is... X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b4e2cd5b9a995e9154b1169e83a0347d257a938c;p=gcc.git [patch AArch64] Do not perform a vector splat for vector initialisation if it is not useful In the testcase in this patch we create an SLP vector with only two elements. Our current vector initialisation code will first duplicate the first element to both lanes, then overwrite the top lane with a new value. This duplication can be clunky and wasteful. Better would be to simply use the fact that we will always be overwriting the remaining bits, and simply move the first element to the corrcet place (implicitly zeroing all other bits). This reduces the code generation for this case, and can allow more efficient addressing modes, and other second order benefits for AArch64 code which has been vectorized to V2DI mode. Note that the change is generic enough to catch the case for any vector mode, but is expected to be most useful for 2x64-bit vectorization. Unfortunately, on its own, this would cause failures in gcc.target/aarch64/load_v2vec_lanes_1.c and gcc.target/aarch64/store_v2vec_lanes.c , which expect to see many more vec_merge and vec_duplicate for their simplifications to apply. To fix this, add a special case to the AArch64 code if we are loading from two memory addresses, and use the load_pair_lanes patterns directly. We also need a new pattern in simplify-rtx.c:simplify_ternary_operation to catch: (vec_merge:OUTER (vec_duplicate:OUTER x:INNER) (subreg:OUTER y:INNER 0) (const_int N)) And simplify it to: (vec_concat:OUTER x:INNER y:INNER) or (vec_concat y x) This is similar to the existing patterns which are tested in this function, without requiring the second operand to also be a vec_duplicate. * config/aarch64/aarch64.c (aarch64_expand_vector_init): Modify code generation for cases where splatting a value is not useful. * simplify-rtx.c (simplify_ternary_operation): Simplify vec_merge across a vec_duplicate and a paradoxical subreg forming a vector mode to a vec_concat. * gcc.target/aarch64/vect-slp-dup.c: New. Co-Authored-By: Kyrylo Tkachov From-SVN: r260309 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index c434149ea37..1a245f78fa4 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,13 @@ +2018-05-17 James Greenhalgh + Kyrylo Tkachov + + * config/aarch64/aarch64.c (aarch64_expand_vector_init): Modify + code generation for cases where splatting a value is not useful. + * simplify-rtx.c (simplify_ternary_operation): Simplify + vec_merge across a vec_duplicate and a paradoxical subreg forming a vector + mode to a vec_concat. + + 2018-05-17 Olga Makhotina * config.gcc: Support "goldmont-plus". diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index a2003fe5287..6bf6c05535b 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -13916,9 +13916,54 @@ aarch64_expand_vector_init (rtx target, rtx vals) maxv = matches[i][1]; } - /* Create a duplicate of the most common element. */ - rtx x = copy_to_mode_reg (inner_mode, XVECEXP (vals, 0, maxelement)); - aarch64_emit_move (target, gen_vec_duplicate (mode, x)); + /* Create a duplicate of the most common element, unless all elements + are equally useless to us, in which case just immediately set the + vector register using the first element. */ + + if (maxv == 1) + { + /* For vectors of two 64-bit elements, we can do even better. */ + if (n_elts == 2 + && (inner_mode == E_DImode + || inner_mode == E_DFmode)) + + { + rtx x0 = XVECEXP (vals, 0, 0); + rtx x1 = XVECEXP (vals, 0, 1); + /* Combine can pick up this case, but handling it directly + here leaves clearer RTL. + + This is load_pair_lanes, and also gives us a clean-up + for store_pair_lanes. */ + if (memory_operand (x0, inner_mode) + && memory_operand (x1, inner_mode) + && !STRICT_ALIGNMENT + && rtx_equal_p (XEXP (x1, 0), + plus_constant (Pmode, + XEXP (x0, 0), + GET_MODE_SIZE (inner_mode)))) + { + rtx t; + if (inner_mode == DFmode) + t = gen_load_pair_lanesdf (target, x0, x1); + else + t = gen_load_pair_lanesdi (target, x0, x1); + emit_insn (t); + return; + } + } + /* The subreg-move sequence below will move into lane zero of the + vector register. For big-endian we want that position to hold + the last element of VALS. */ + maxelement = BYTES_BIG_ENDIAN ? n_elts - 1 : 0; + rtx x = copy_to_mode_reg (inner_mode, XVECEXP (vals, 0, maxelement)); + aarch64_emit_move (target, lowpart_subreg (mode, x, inner_mode)); + } + else + { + rtx x = copy_to_mode_reg (inner_mode, XVECEXP (vals, 0, maxelement)); + aarch64_emit_move (target, gen_vec_duplicate (mode, x)); + } /* Insert the rest. */ for (int i = 0; i < n_elts; i++) diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index e96c9d1b441..d2714db7ae8 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -5891,6 +5891,60 @@ simplify_ternary_operation (enum rtx_code code, machine_mode mode, return simplify_gen_binary (VEC_CONCAT, mode, newop0, newop1); } + /* Replace: + + (vec_merge:outer (vec_duplicate:outer x:inner) + (subreg:outer y:inner 0) + (const_int N)) + + with (vec_concat:outer x:inner y:inner) if N == 1, + or (vec_concat:outer y:inner x:inner) if N == 2. + + Implicitly, this means we have a paradoxical subreg, but such + a check is cheap, so make it anyway. + + Only applies for vectors of two elements. */ + if (GET_CODE (op0) == VEC_DUPLICATE + && GET_CODE (op1) == SUBREG + && GET_MODE (op1) == GET_MODE (op0) + && GET_MODE (SUBREG_REG (op1)) == GET_MODE (XEXP (op0, 0)) + && paradoxical_subreg_p (op1) + && subreg_lowpart_p (op1) + && known_eq (GET_MODE_NUNITS (GET_MODE (op0)), 2) + && known_eq (GET_MODE_NUNITS (GET_MODE (op1)), 2) + && IN_RANGE (sel, 1, 2)) + { + rtx newop0 = XEXP (op0, 0); + rtx newop1 = SUBREG_REG (op1); + if (sel == 2) + std::swap (newop0, newop1); + return simplify_gen_binary (VEC_CONCAT, mode, newop0, newop1); + } + + /* Same as above but with switched operands: + Replace (vec_merge:outer (subreg:outer x:inner 0) + (vec_duplicate:outer y:inner) + (const_int N)) + + with (vec_concat:outer x:inner y:inner) if N == 1, + or (vec_concat:outer y:inner x:inner) if N == 2. */ + if (GET_CODE (op1) == VEC_DUPLICATE + && GET_CODE (op0) == SUBREG + && GET_MODE (op0) == GET_MODE (op1) + && GET_MODE (SUBREG_REG (op0)) == GET_MODE (XEXP (op1, 0)) + && paradoxical_subreg_p (op0) + && subreg_lowpart_p (op0) + && known_eq (GET_MODE_NUNITS (GET_MODE (op1)), 2) + && known_eq (GET_MODE_NUNITS (GET_MODE (op0)), 2) + && IN_RANGE (sel, 1, 2)) + { + rtx newop0 = SUBREG_REG (op0); + rtx newop1 = XEXP (op1, 0); + if (sel == 2) + std::swap (newop0, newop1); + return simplify_gen_binary (VEC_CONCAT, mode, newop0, newop1); + } + /* Replace (vec_merge (vec_duplicate x) (vec_duplicate y) (const_int n)) with (vec_concat x y) or (vec_concat y x) depending on value diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index f36006744f9..fe495f8be7e 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2018-05-17 James Greenhalgh + + * gcc.target/aarch64/vect-slp-dup.c: New. + 2018-05-17 Paolo Carlini PR c++/85713 diff --git a/gcc/testsuite/gcc.target/aarch64/vect-slp-dup.c b/gcc/testsuite/gcc.target/aarch64/vect-slp-dup.c new file mode 100644 index 00000000000..0541e480d1f --- /dev/null +++ b/gcc/testsuite/gcc.target/aarch64/vect-slp-dup.c @@ -0,0 +1,20 @@ +/* { dg-do compile } */ + +/* { dg-options "-O3 -ftree-vectorize -fno-vect-cost-model" } */ + +void bar (double); + +void +foo (double *restrict in, double *restrict in2, + double *restrict out1, double *restrict out2) +{ + for (int i = 0; i < 1024; i++) + { + out1[i] = in[i] + 2.0 * in[i+128]; + out1[i+1] = in[i+1] + 2.0 * in2[i]; + bar (in[i]); + } +} + +/* { dg-final { scan-assembler-not "dup\tv\[0-9\]+.2d, v\[0-9\]+" } } */ +