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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-10012] tree-optimization/111764 - wrong reduction vectorization Date: Mon, 27 Nov 2023 13:09:47 +0000 (GMT) [thread overview] Message-ID: <20231127130947.9C38538582B8@sourceware.org> (raw) https://gcc.gnu.org/g:bd75062cc3fc4abd19c37fae164d9764ffab2407 commit r12-10012-gbd75062cc3fc4abd19c37fae164d9764ffab2407 Author: Richard Biener <rguenther@suse.de> Date: Thu Oct 12 09:09:46 2023 +0200 tree-optimization/111764 - wrong reduction vectorization The following removes a misguided attempt to allow x + x in a reduction path, also allowing x * x which isn't valid. x + x actually never arrives this way but instead is canonicalized to 2 * x. This makes reduction path handling consistent with how we handle the single-stmt reduction case. PR tree-optimization/111764 * tree-vect-loop.cc (check_reduction_path): Remove the attempt to allow x + x via special-casing of assigns. * gcc.dg/vect/pr111764.c: New testcase. (cherry picked from commit 05f98310b54da95e468d799f4a910174320cccbb) Diff: --- gcc/testsuite/gcc.dg/vect/pr111764.c | 16 ++++++++++++++++ gcc/tree-vect-loop.cc | 15 +++------------ 2 files changed, 19 insertions(+), 12 deletions(-) diff --git a/gcc/testsuite/gcc.dg/vect/pr111764.c b/gcc/testsuite/gcc.dg/vect/pr111764.c new file mode 100644 index 00000000000..f4e110f3bbf --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/pr111764.c @@ -0,0 +1,16 @@ +#include "tree-vect.h" + +short b = 2; + +int main() +{ + check_vect (); + + for (int a = 1; a <= 9; a++) + b = b * b; + if (b != 0) + __builtin_abort (); + + return 0; +} + diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc index 9df2d5690b7..e1681047d9d 100644 --- a/gcc/tree-vect-loop.cc +++ b/gcc/tree-vect-loop.cc @@ -3513,24 +3513,15 @@ pop: ??? We could relax this and handle arbitrary live stmts by forcing a scalar epilogue for example. */ imm_use_iterator imm_iter; + use_operand_p use_p; gimple *op_use_stmt; unsigned cnt = 0; FOR_EACH_IMM_USE_STMT (op_use_stmt, imm_iter, op.ops[opi]) if (!is_gimple_debug (op_use_stmt) && (*code != ERROR_MARK || flow_bb_inside_loop_p (loop, gimple_bb (op_use_stmt)))) - { - /* We want to allow x + x but not x < 1 ? x : 2. */ - if (is_gimple_assign (op_use_stmt) - && gimple_assign_rhs_code (op_use_stmt) == COND_EXPR) - { - use_operand_p use_p; - FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter) - cnt++; - } - else - cnt++; - } + FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter) + cnt++; if (cnt != 1) { fail = true;
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