From 1fd319753c90f05e026e16c2c83af8f1c6687a5f Mon Sep 17 00:00:00 2001 From: Kyrylo Tkachov Date: Mon, 19 Nov 2018 17:58:00 +0000 Subject: [PATCH] Disable unrolling for loops vectorised with non-constant VF This is an alternative to https://gcc.gnu.org/ml/gcc-patches/2018-11/msg00694.html As richi suggested, this disables unrolling of loops vectorised with variable-length SVE in the vectoriser itself through the loop->unroll member. It took me a few tries to get it right, as it needs to be set to '1' to disable unrolling, the rationale for that mechanism is described in the comment in cfgloop.h. * tree-vect-loop.c (vect_transform_loop): Disable further unrolling of the loop if vf is non-constant. * gcc.target/aarch64/sve/unroll-1.c: New test. From-SVN: r266281 --- gcc/ChangeLog | 5 +++++ gcc/testsuite/ChangeLog | 4 ++++ gcc/testsuite/gcc.target/aarch64/sve/unroll-1.c | 13 +++++++++++++ gcc/tree-vect-loop.c | 9 +++++++++ 4 files changed, 31 insertions(+) create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/unroll-1.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 126f168a15d..99968490f63 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2018-11-19 Kyrylo Tkachov + + * tree-vect-loop.c (vect_transform_loop): Disable further unrolling + of the loop if vf is non-constant. + 2018-11-19 David Malcolm PR tree-optimization/87025 diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index cea66a545f1..ba1c5d68aa0 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2018-11-19 Kyrylo Tkachov + + * gcc.target/aarch64/sve/unroll-1.c: New test. + 2018-11-19 David Malcolm PR tree-optimization/87025 diff --git a/gcc/testsuite/gcc.target/aarch64/sve/unroll-1.c b/gcc/testsuite/gcc.target/aarch64/sve/unroll-1.c new file mode 100644 index 00000000000..d4353009e21 --- /dev/null +++ b/gcc/testsuite/gcc.target/aarch64/sve/unroll-1.c @@ -0,0 +1,13 @@ +/* { dg-do compile } */ +/* { dg-options "-O3" } */ + +/* Check that simple loop is not fully unrolled. */ + +void +fully_peel_me (double *x) +{ + for (int i = 0; i < 5; i++) + x[i] = x[i] * 2; +} + +/* { dg-final { scan-assembler-times {b..\t\.L.\n} 1 } } */ diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c index 81d8d466637..07a22d787c4 100644 --- a/gcc/tree-vect-loop.c +++ b/gcc/tree-vect-loop.c @@ -8515,6 +8515,15 @@ vect_transform_loop (loop_vec_info loop_vinfo) } } + /* Loops vectorized with a variable factor won't benefit from + unrolling/peeling. */ + if (!vf.is_constant ()) + { + loop->unroll = 1; + if (dump_enabled_p ()) + dump_printf_loc (MSG_NOTE, vect_location, "Disabling unrolling due to" + " variable-length vectorization factor\n"); + } /* Free SLP instances here because otherwise stmt reference counting won't work. */ slp_instance instance; -- 2.30.2