From 1393938e4c7dab9306cdce5a73d93b242fc246ec Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Wed, 31 Mar 2021 11:26:06 +0100 Subject: [PATCH] aarch64: Fix target alignment for SVE [PR98119] The vectoriser supports peeling for alignment using predication: we move back to the previous aligned boundary and make the skipped elements inactive in the first loop iteration. As it happens, the costs for existing CPUs give an equal cost to aligned and unaligned accesses, so this feature is rarely used. However, the PR shows that when the feature was forced on, we were still trying to align to a full-vector boundary even when using partial vectors. gcc/ PR target/98119 * config/aarch64/aarch64.c (aarch64_vectorize_preferred_vector_alignment): Query the size of the provided SVE vector; do not assume that all SVE vectors have the same size. gcc/testsuite/ PR target/98119 * gcc.target/aarch64/sve/pr98119.c: New test. --- gcc/config/aarch64/aarch64.c | 7 ++++--- gcc/testsuite/gcc.target/aarch64/sve/pr98119.c | 13 +++++++++++++ 2 files changed, 17 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr98119.c diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index 5eda9e8..f878721 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -20275,10 +20275,11 @@ aarch64_vectorize_preferred_vector_alignment (const_tree type) { if (aarch64_sve_data_mode_p (TYPE_MODE (type))) { - /* If the length of the vector is fixed, try to align to that length, - otherwise don't try to align at all. */ + /* If the length of the vector is a fixed power of 2, try to align + to that length, otherwise don't try to align at all. */ HOST_WIDE_INT result; - if (!BITS_PER_SVE_VECTOR.is_constant (&result)) + if (!GET_MODE_BITSIZE (TYPE_MODE (type)).is_constant (&result) + || !pow2p_hwi (result)) result = TYPE_ALIGN (TREE_TYPE (type)); return result; } diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr98119.c b/gcc/testsuite/gcc.target/aarch64/sve/pr98119.c new file mode 100644 index 0000000..da6208c --- /dev/null +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr98119.c @@ -0,0 +1,13 @@ +/* { dg-options "-O3 -msve-vector-bits=512 -mtune=thunderx" } */ + +void +f (unsigned short *x) +{ + for (int i = 0; i < 1000; ++i) + x[i] += x[i - 16]; +} + +/* { dg-final { scan-assembler-not {\tubfx\t[wx][0-9]+, [wx][0-9]+, #?1, #?5\n} } } */ +/* { dg-final { scan-assembler-not {\tand\tx[0-9]+, x[0-9]+, #?-63\n} } } */ +/* { dg-final { scan-assembler {\tubfx\t[wx][0-9]+, [wx][0-9]+, #?1, #?4\n} } } */ +/* { dg-final { scan-assembler {\tand\tx[0-9]+, x[0-9]+, #?-31\n} } } */ -- 2.7.4