tree-optimization: Fix tree dse of __*_chk PR93262

The following testcase shows that GCC trunk mishandles DSE of __*_chk
calls.  Tail trimming of the calls is fine, we want to just decrease the
third argument and keep the first two and last arguments unmodified.
But for head trimming, we currently increment the two by head_trim and
decrease the third by head_trim, so
  __builtin___memcpy_chk (&a, b_2(D), 48, 32);
  __builtin_memset (&a, 32, 16);
into:
  _5 = b_2(D) + 16;
  __builtin___memcpy_chk (&MEM <char> [(void *)&a + 16B], _5, 32, 32);
  __builtin_memset (&a, 32, 16);
This is wrong, because the 32 was the determined (maximum) size of the
destination (char a[32]), but &a[16] has maximum size of 16, not 32.
The __builtin___memcpy_chk (&MEM <char> [(void *)&a + 16B], _5, 32, 32);
call is just folded later into
__builtin_memcpy (&MEM <char> [(void *)&a + 16B], _5, 32);
because it says that it copies as many bytes into destination as the
destination has.  We need:
  __builtin___memcpy_chk (&MEM <char> [(void *)&a + 16B], _5, 32, 16);
instead, which will terminate the program instead of letting it silently
overflow the buffer.
The patch just punts if we'd need to decrease the last argument below 0.

Fortunately, release branches are unaffected.
P.S. it was quite hard to make the runtime test working, in builtins.exp
neither dg-options nor dg-additional-options work and builtins.exp adds
-fno-tree-dse among several other -fno-* options.  Fortunately optimize
attribute works.

2020-01-15  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/93262
	* tree-ssa-dse.c (maybe_trim_memstar_call): For *_chk builtins,
	perform head trimming only if the last argument is constant,
	either all ones, or larger or equal to head trim, in the latter
	case decrease the last argument by head_trim.

	* gcc.c-torture/execute/builtins/pr93262-chk.c: New test.
	* gcc.c-torture/execute/builtins/pr93262-chk-lib.c: New file.
	* gcc.c-torture/execute/builtins/pr93262-chk.x: New file.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8f4382030b94ca82d613eb1b2580f41b94374631..56e7995305ee4c9e63e2c6ac620b26de7cfdda75 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,11 @@
 2020-01-15  Jakub Jelinek  <jakub@redhat.com>
 
+       PR tree-optimization/93262
+       * tree-ssa-dse.c (maybe_trim_memstar_call): For *_chk builtins,
+       perform head trimming only if the last argument is constant,
+       either all ones, or larger or equal to head trim, in the latter
+       case decrease the last argument by head_trim.
+
        PR tree-optimization/93249
        * tree-ssa-dse.c: Include builtins.h and gimple-fold.h.
        (maybe_trim_memstar_call): Move head_trim and tail_trim vars to

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 77d573fed2873d23dbbc794e9cc346f72e8e8378..2e59f2861c83cad391a31e3a6dce85e65c92eeb3 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2020-01-15  Jakub Jelinek  <jakub@redhat.com>
 
+       PR tree-optimization/93262
+       * gcc.c-torture/execute/builtins/pr93262-chk.c: New test.
+       * gcc.c-torture/execute/builtins/pr93262-chk-lib.c: New file.
+       * gcc.c-torture/execute/builtins/pr93262-chk.x: New file.
+
        PR tree-optimization/93249
        * gcc.c-torture/execute/pr93249.c: New test.
 

diff --git a/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk-lib.c b/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk-lib.c
new file mode 100644 (file)
index 0000000..9daf13e
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk-lib.c
@@ -0,0 +1 @@
+#include "lib/chk.c"

diff --git a/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk.c b/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk.c
new file mode 100644 (file)
index 0000000..66d86b4
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk.c
@@ -0,0 +1,55 @@
+/* PR tree-optimization/93262 */
+
+extern void abort (void);
+typedef __SIZE_TYPE__ size_t;
+extern void *memcpy (void *, const void *, size_t);
+extern void *memset (void *, int, size_t);
+
+#include "chk.h"
+
+char b[32] = "def";
+char a[32] = "abc";
+char c[32] = "ghi";
+int l1;
+
+__attribute__((noipa, noinline, noclone, optimize ("tree-dse"))) void
+foo (char *b)
+{
+  memcpy (a, b, 48);
+  memset (a, ' ', 16);
+}
+
+__attribute__((noipa, noinline, noclone, optimize ("tree-dse"))) void
+bar (void)
+{
+  memset (a, ' ', 48);
+  memset (a, '0', 16);
+}
+
+void
+main_test (void)
+{
+#ifndef __OPTIMIZE__
+  /* Object size checking is only intended for -O[s123].  */
+  return;
+#endif
+  __asm ("" : "=r" (l1) : "0" (l1));
+  chk_calls = 0;
+  chk_fail_allowed = 1;
+  /* Runtime checks.  */
+  if (__builtin_setjmp (chk_fail_buf) == 0)
+    {
+      foo ("0123456789abcdeffedcba9876543210ghijklmnopqrstuv");
+      if (!l1)
+       abort ();
+    }
+  if (__builtin_setjmp (chk_fail_buf) == 0)
+    {
+      bar ();
+      if (!l1)
+       abort ();
+    }
+  if (chk_calls != 2)
+    abort ();
+  return 0;
+}

diff --git a/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk.x b/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk.x
new file mode 100644 (file)
index 0000000..6f4746d
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/builtins/pr93262-chk.x
@@ -0,0 +1,7 @@
+load_lib target-supports.exp
+
+if { ! [check_effective_target_nonlocal_goto] } {
+    return 1
+}
+
+return 0

diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c
index cb64d6fe83a64efa5ac3d3d022a4b14d3b661501..374143e5785e10b15f0e53c8910bde5ba701dbc3 100644 (file)
--- a/gcc/tree-ssa-dse.c
+++ b/gcc/tree-ssa-dse.c
@@ -508,6 +508,22 @@ maybe_trim_memstar_call (ao_ref *ref, sbitmap live, gimple *stmt)
       /* Head trimming requires adjusting all the arguments.  */
       if (head_trim)
        {
+         /* For __*_chk need to adjust also the last argument.  */
+         if (gimple_call_num_args (stmt) == 4)
+           {
+             tree size = gimple_call_arg (stmt, 3);
+             if (!tree_fits_uhwi_p (size))
+               break;
+             if (!integer_all_onesp (size))
+               {
+                 unsigned HOST_WIDE_INT sz = tree_to_uhwi (size);
+                 if (sz < (unsigned) head_trim)
+                   break;
+                 tree arg = wide_int_to_tree (TREE_TYPE (size),
+                                              sz - head_trim);
+                 gimple_call_set_arg (stmt, 3, arg);
+               }
+           }
          tree *dst = gimple_call_arg_ptr (stmt, 0);
          increment_start_addr (stmt, dst, head_trim);
          tree *src = gimple_call_arg_ptr (stmt, 1);
@@ -527,6 +543,22 @@ maybe_trim_memstar_call (ao_ref *ref, sbitmap live, gimple *stmt)
       /* Head trimming requires adjusting all the arguments.  */
       if (head_trim)
        {
+         /* For __*_chk need to adjust also the last argument.  */
+         if (gimple_call_num_args (stmt) == 4)
+           {
+             tree size = gimple_call_arg (stmt, 3);
+             if (!tree_fits_uhwi_p (size))
+               break;
+             if (!integer_all_onesp (size))
+               {
+                 unsigned HOST_WIDE_INT sz = tree_to_uhwi (size);
+                 if (sz < (unsigned) head_trim)
+                   break;
+                 tree arg = wide_int_to_tree (TREE_TYPE (size),
+                                              sz - head_trim);
+                 gimple_call_set_arg (stmt, 3, arg);
+               }
+           }
          tree *dst = gimple_call_arg_ptr (stmt, 0);
          increment_start_addr (stmt, dst, head_trim);
          decrement_count (stmt, head_trim);