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From: Richard Sandiford <rsandifo@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2737] vect: Fix missed gather load opportunity Date: Tue, 20 Sep 2022 14:27:58 +0000 (GMT) [thread overview] Message-ID: <20220920142758.5B2D8385803D@sourceware.org> (raw) https://gcc.gnu.org/g:4a773bf2f08656a39ac75cf6b4871c8cec8b5007 commit r13-2737-g4a773bf2f08656a39ac75cf6b4871c8cec8b5007 Author: Richard Sandiford <richard.sandiford@arm.com> Date: Tue Sep 20 15:27:46 2022 +0100 vect: Fix missed gather load opportunity While writing a testcase for PR106794, I noticed that we failed to vectorise the testcase in the patch for SVE. The code that recognises gather loads tries to optimise the point at which the offset is calculated, to avoid unnecessary extensions or truncations: /* Don't include the conversion if the target is happy with the current offset type. */ But breaking only makes sense if we're at an SSA_NAME (which could then be vectorised). We shouldn't break on a conversion embedded in a generic expression. gcc/ * tree-vect-data-refs.cc (vect_check_gather_scatter): Restrict early-out optimisation to SSA_NAMEs. gcc/testsuite/ * gcc.dg/vect/vect-gather-5.c: New test. Diff: --- gcc/testsuite/gcc.dg/vect/vect-gather-5.c | 42 +++++++++++++++++++++++++++++++ gcc/tree-vect-data-refs.cc | 1 + 2 files changed, 43 insertions(+) diff --git a/gcc/testsuite/gcc.dg/vect/vect-gather-5.c b/gcc/testsuite/gcc.dg/vect/vect-gather-5.c new file mode 100644 index 00000000000..8b5074bba88 --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/vect-gather-5.c @@ -0,0 +1,42 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-O3" } */ + +#ifdef __aarch64__ +#pragma GCC target "+sve" +#endif + +long a[100], b[100], c[100]; + +void g1 () +{ + for (int i = 0; i < 100; i += 2) + { + c[i] += a[b[i]] + 1; + c[i + 1] += a[b[i + 1]] + 2; + } +} + +long g2 () +{ + long res = 0; + for (int i = 0; i < 100; i += 2) + { + res += a[b[i + 1]]; + res += a[b[i]]; + } + return res; +} + +long g3 () +{ + long res = 0; + for (int i = 0; i < 100; i += 2) + { + res += a[b[i]]; + res += a[b[i + 1]]; + } + return res; +} + +/* { dg-final { scan-tree-dump-times {add new stmt[^\n]*GATHER_LOAD} 3 "vect" { target aarch64*-*-* } } } */ +/* { dg-final { scan-tree-dump-not {add new stmt[^\n]*VEC_PERM_EXPR} "vect" { target aarch64*-*-* } } } */ diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc index b279a82551e..e03b50498d1 100644 --- a/gcc/tree-vect-data-refs.cc +++ b/gcc/tree-vect-data-refs.cc @@ -4151,6 +4151,7 @@ vect_check_gather_scatter (stmt_vec_info stmt_info, loop_vec_info loop_vinfo, /* Don't include the conversion if the target is happy with the current offset type. */ if (use_ifn_p + && TREE_CODE (off) == SSA_NAME && !POINTER_TYPE_P (TREE_TYPE (off)) && vect_gather_scatter_fn_p (loop_vinfo, DR_IS_READ (dr), masked_p, vectype, memory_type,
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