Richard Biener <rguent...@suse.de> writes:
> The following fixes a problem with my last attempt of avoiding
> out-of-bound shift values for vectorized right shifts of widened
> operands. Instead of truncating the shift amount with a bitwise
> and we actually need to saturate it to the target precision.
>
> The following does that and adds test coverage for the constant
> and invariant but variable case that would previously have failed.
>
> Bootstrap & regtest on x86_64-unknown-linux-gnu in progress, I plan
> to push this soon, just in case you have any comments here.
LGTM FWIW.
Richard
> Richard.
>
> PR tree-optimization/110838
> * tree-vect-patterns.cc (vect_recog_over_widening_pattern):
> Fix right-shift value sanitizing. Properly emit external
> def mangling in the preheader rather than in the pattern
> def sequence where it will fail vectorizing.
>
> * gcc.dg/vect/pr110838.c: New testcase.
> ---
> gcc/testsuite/gcc.dg/vect/pr110838.c | 31 ++++++++++++++++++++++++++++
> gcc/tree-vect-patterns.cc | 22 +++++++++++++++-----
> 2 files changed, 48 insertions(+), 5 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/pr110838.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/pr110838.c
> b/gcc/testsuite/gcc.dg/vect/pr110838.c
> new file mode 100644
> index 00000000000..cf8765be603
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr110838.c
> @@ -0,0 +1,31 @@
> +/* { dg-do run } */
> +
> +#include "tree-vect.h"
> +
> +short a[32], b[32];
> +
> +void __attribute__((noipa)) foo ()
> +{
> + for (int i = 0; i < 32; ++i)
> + a[i] = b[i] >> 16;
> +}
> +
> +void __attribute__((noipa)) bar (int n)
> +{
> + int np = n & 31;
> + for (int i = 0; i < 32; ++i)
> + a[i] = b[i] >> np;
> +}
> +
> +int main ()
> +{
> + check_vect ();
> + b[0] = -8;
> + foo ();
> + if (a[0] != -1)
> + abort ();
> + bar (16);
> + if (a[0] != -1)
> + abort ();
> + return 0;
> +}
> diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
> index e4ab8c2d65b..2cedf238450 100644
> --- a/gcc/tree-vect-patterns.cc
> +++ b/gcc/tree-vect-patterns.cc
> @@ -3109,8 +3109,8 @@ vect_recog_over_widening_pattern (vec_info *vinfo,
> wide_int min_value, max_value;
> if (TREE_CODE (ops[1]) == INTEGER_CST)
> ops[1] = wide_int_to_tree (op_type,
> - wi::bit_and (wi::to_wide (ops[1]),
> - new_precision - 1));
> + wi::umin (wi::to_wide (ops[1]),
> + new_precision - 1));
> else if (!vect_get_range_info (ops[1], &min_value, &max_value)
> || wi::ge_p (max_value, new_precision, TYPE_SIGN (op_type)))
> {
> @@ -3118,11 +3118,23 @@ vect_recog_over_widening_pattern (vec_info *vinfo,
> same argument widened shifts and it un-CSEs same arguments. */
> tree new_var = vect_recog_temp_ssa_var (op_type, NULL);
> gimple *pattern_stmt
> - = gimple_build_assign (new_var, BIT_AND_EXPR, ops[1],
> + = gimple_build_assign (new_var, MIN_EXPR, ops[1],
> build_int_cst (op_type, new_precision - 1));
> - ops[1] = new_var;
> gimple_set_location (pattern_stmt, gimple_location (last_stmt));
> - append_pattern_def_seq (vinfo, last_stmt_info, pattern_stmt);
> + if (unprom[1].dt == vect_external_def)
> + {
> + if (edge e = vect_get_external_def_edge (vinfo, ops[1]))
> + {
> + basic_block new_bb
> + = gsi_insert_on_edge_immediate (e, pattern_stmt);
> + gcc_assert (!new_bb);
> + }
> + else
> + return NULL;
> + }
> + else
> + append_pattern_def_seq (vinfo, last_stmt_info, pattern_stmt);
> + ops[1] = new_var;
> }
> }
