From 6b6bd53619fd11bab3def8dee737711a7ee539ea Mon Sep 17 00:00:00 2001 From: Robin Dapp Date: Thu, 8 Aug 2024 12:54:36 +0200 Subject: [PATCH] tree-ifcvt: Add zero maskload else value. When predicating a load we implicitly assume that the else value is zero. This matters in case the loaded value is padded (like e.g. a Bool) and we must ensure that the padding bytes are zero on targets that don't implicitly zero inactive elements. A former version of this patch still had this handling in ifcvt but the latest version defers it to the vectorizer. gcc/ChangeLog: * tree-if-conv.cc (predicate_load_or_store): Add zero else operand and comment. --- gcc/tree-if-conv.cc | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/gcc/tree-if-conv.cc b/gcc/tree-if-conv.cc index eb981642bae..f1a1f8fd0d3 100644 --- a/gcc/tree-if-conv.cc +++ b/gcc/tree-if-conv.cc @@ -2555,9 +2555,17 @@ predicate_load_or_store (gimple_stmt_iterator *gsi, gassign *stmt, tree mask) ref); if (TREE_CODE (lhs) == SSA_NAME) { + /* Get a zero else value. This might not be what a target actually uses + but we cannot be sure about which vector mode the vectorizer will + choose. Therefore, leave the decision whether we need to force the + inactive elements to zero to the vectorizer. */ + tree els = vect_get_mask_load_else (MASK_LOAD_ELSE_ZERO, + TREE_TYPE (lhs)); + new_stmt - = gimple_build_call_internal (IFN_MASK_LOAD, 3, addr, - ptr, mask); + = gimple_build_call_internal (IFN_MASK_LOAD, 4, addr, + ptr, mask, els); + gimple_call_set_lhs (new_stmt, lhs); gimple_set_vuse (new_stmt, gimple_vuse (stmt)); }