https://gcc.gnu.org/g:94f275432f7ea4781ec7c05fa9d1d81ef6cb3fc1
commit r16-22-g94f275432f7ea4781ec7c05fa9d1d81ef6cb3fc1
Author: Andrew Pinski <quic_apin...@quicinc.com>
Date: Thu Feb 20 16:09:05 2025 -0800
gimple-fold: Improve optimize_memcpy_to_memset to handle STRING_CST
[PR78408]
While looking into PR 118947, I noticed that optimize_memcpy_to_memset
didn't
handle STRING_CST which are also used for a memset of 0 but for char arrays.
This fixes that and improves optimize_memcpy_to_memset to handle that case.
This fixes part of PR 118947 but not the whole thing; we still need to skip
over
vdefs in some cases.
Boostrapped and tested on x86_64-linux-gnu.
PR tree-optimization/78408
PR tree-optimization/118947
gcc/ChangeLog:
* gimple-fold.cc (optimize_memcpy_to_memset): Handle STRING_CST
case too.
gcc/testsuite/ChangeLog:
* gcc.dg/pr78408-3.c: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
Diff:
---
gcc/gimple-fold.cc | 17 +++++++++++++++++
gcc/testsuite/gcc.dg/pr78408-3.c | 14 ++++++++++++++
2 files changed, 31 insertions(+)
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index b64561396874..3e6b53d6a0f1 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -919,6 +919,23 @@ optimize_memcpy_to_memset (gimple_stmt_iterator *gsip,
tree dest, tree src, tree
poly_int64 offset, offset2;
tree val = integer_zero_node;
if (gimple_store_p (defstmt)
+ && gimple_assign_single_p (defstmt)
+ && TREE_CODE (gimple_assign_rhs1 (defstmt)) == STRING_CST
+ && !gimple_clobber_p (defstmt))
+ {
+ tree str = gimple_assign_rhs1 (defstmt);
+ src2 = gimple_assign_lhs (defstmt);
+ /* The string must contain all null char's for now. */
+ for (int i = 0; i < TREE_STRING_LENGTH (str); i++)
+ {
+ if (TREE_STRING_POINTER (str)[i] != 0)
+ {
+ src2 = NULL_TREE;
+ break;
+ }
+ }
+ }
+ else if (gimple_store_p (defstmt)
&& gimple_assign_single_p (defstmt)
&& TREE_CODE (gimple_assign_rhs1 (defstmt)) == CONSTRUCTOR
&& !gimple_clobber_p (defstmt))
diff --git a/gcc/testsuite/gcc.dg/pr78408-3.c b/gcc/testsuite/gcc.dg/pr78408-3.c
new file mode 100644
index 000000000000..3de90d023923
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr78408-3.c
@@ -0,0 +1,14 @@
+/* PR tree-optimization/78408 */
+/* { dg-do compile { target size32plus } } */
+/* { dg-options "-O2 -fdump-tree-forwprop1-details" } */
+/* { dg-final { scan-tree-dump-times "after previous" 1 "forwprop1" } } */
+
+void* aaa();
+void* bbb()
+{
+ void* ret = aaa();
+ char buf[32] = {};
+ __builtin_memcpy(ret, buf, 32);
+ return ret;
+}
+
