From e13f37d9f7600d337f8a4589b5f985ded9e05852 Mon Sep 17 00:00:00 2001
From: Martin Sebor <msebor@redhat.com>
Date: Mon, 13 Jan 2020 13:20:41 +0000
Subject: [PATCH] PR tree-optimization/93213 - wrong code with -Og
-foptimize-strlen
gcc/testsuite/ChangeLog:
PR tree-optimization/93213
* gcc.c-torture/execute/pr93213.c: New test.
gcc/ChangeLog:
PR tree-optimization/93213
* tree-ssa-strlen.c (handle_store): Only allow single-byte nul-over-nul
stores to be eliminated.
---
gcc/ChangeLog | 6 +++
gcc/testsuite/ChangeLog | 5 ++
gcc/testsuite/gcc.c-torture/execute/pr93213.c | 50 +++++++++++++++++++
gcc/tree-ssa-strlen.c | 6 +--
4 files changed, 64 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr93213.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fc25469452c6..2a4b03a32d31 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-01-13 Martin Sebor <msebor@redhat.com>
+
+ PR tree-optimization/93213
+ * tree-ssa-strlen.c (handle_store): Only allow single-byte nul-over-nul
+ stores to be eliminated.
+
2020-01-13 Martin Liska <mliska@suse.cz>
* opts.c (print_help): Do not print CL_PARAM
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index cccc2853ed59..f14638c5079a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-01-13 Martin Sebor <msebor@redhat.com>
+
+ PR tree-optimization/93213
+ * gcc.c-torture/execute/pr93213.c: New test.
+
2020-01-10 Thomas Schwinge <thomas@codesourcery.com>
* c-c++-common/goacc/host_data-1.c: Extend.
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr93213.c b/gcc/testsuite/gcc.c-torture/execute/pr93213.c
new file mode 100644
index 000000000000..86d0465bf67c
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr93213.c
@@ -0,0 +1,50 @@
+/* PR tree-optimization/93213 - wrong code on a multibyte store with
+ -Og -foptimize-strlen
+ { dg-require-effective-target int128 }
+ { dg-additional-options "-Og -foptimize-strlen" } */
+
+typedef unsigned __INT16_TYPE__ u16;
+typedef unsigned __INT32_TYPE__ u32;
+typedef unsigned __int128 u128;
+
+static inline u128
+foo (u16 u16_1, u32 u32_1, u128 u128_1)
+{
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ u128 u128_0 = 0;
+ u128_1 -= __builtin_mul_overflow (u32_1, u16_1, &u32_1);
+ __builtin_memmove (&u16_1, &u128_0, 2);
+ __builtin_memmove (&u16_1, &u128_1, 1);
+ return u16_1;
+#else
+ return 0xff;
+#endif
+}
+
+__attribute__ ((noipa)) void
+bar (void)
+{
+ char a[] = { 1, 2 };
+ const char b[] = { 0, 0 };
+ const char c[] = { 2 };
+ __builtin_memcpy (a, b, 2);
+ // The above is transformed into
+ // MEM <short unsigned int> [(char * {ref-all})&a] = 0;
+ // which was then dropped because of the non-nul store below.
+ __builtin_memcpy (a, c, 1);
+
+ volatile char *p = a;
+ if (p[0] != 2 || p[1] != 0)
+ __builtin_abort ();
+}
+
+int
+main (void)
+{
+ u16 x = foo (-1, -1, 0);
+ if (x != 0xff)
+ __builtin_abort ();
+
+ bar ();
+ return 0;
+}
diff --git a/gcc/tree-ssa-strlen.c b/gcc/tree-ssa-strlen.c
index 4f2a0ad6a198..ad9e98973b12 100644
--- a/gcc/tree-ssa-strlen.c
+++ b/gcc/tree-ssa-strlen.c
@@ -5239,10 +5239,10 @@ handle_store (gimple_stmt_iterator *gsi, bool *zero_write,
}
}
- if (si != NULL && offset == 0 && storing_all_zeros_p)
+ if (si != NULL && offset == 0 && storing_all_zeros_p && lenrange[2] == 1)
{
- /* Allow adjust_last_stmt to remove it if the stored '\0'
- is immediately overwritten. */
+ /* For single-byte stores only, allow adjust_last_stmt to remove
+ the statement if the stored '\0' is immediately overwritten. */
laststmt.stmt = stmt;
laststmt.len = build_int_cst (size_type_node, 1);
laststmt.stridx = si->idx;
--
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