From 6b6bd53619fd11bab3def8dee737711a7ee539ea Mon Sep 17 00:00:00 2001
From: Robin Dapp <rdapp@ventanamicro.com>
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 eb981642bae1..f1a1f8fd0d35 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));
}
--
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