Make tree-ssa-strlen.c handle partial unterminated strings

tree-ssa-strlen.c looks for cases in which a string is built up using
operations like:

    memcpy (a, "foo", 4);
    memcpy (a + 3, "bar", 4);
    int x = strlen (a);

As a side-effect, it optimises the non-final memcpys so that they don't
include the nul terminator.

However, after removing some "& ~0x1"s from tree-ssa-dse.c, the DSE pass
does this optimisation itself (because it can tell that later memcpys
overwrite the terminators).  The strlen pass wasn't able to handle these
pre-optimised calls in the same way as the unoptimised ones.

This patch adds support for tracking unterminated strings.

[Based on the code ARM contributed in branches/ARM/sve-branch@246236]

2017-07-02  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* tree-ssa-strlen.c (strinfo): Rename the length field to
	nonzero_chars.  Add a full_string_p field.
	(compare_nonzero_chars, zero_length_string_p): New functions.
	(get_addr_stridx): Add an offset_out parameter.
	Use compare_nonzero_chars.
	(get_stridx): Update accordingly.  Use compare_nonzero_chars.
	(new_strinfo): Update after above changes to strinfo.
	(set_endptr_and_length): Set full_string_p.
	(get_string_length): Update after above changes to strinfo.
	(unshare_strinfo): Update call to new_strinfo.
	(maybe_invalidate): Likewise.
	(get_stridx_plus_constant): Change off to unsigned HOST_WIDE_INT.
	Use compare_nonzero_chars and zero_string_p.  Treat nonzero_chars
	as a uhwi instead of an shwi.  Update after above changes to
	strinfo and new_strinfo.
	(zero_length_string): Assert that chainsi contains full strings.
	Use zero_length_string_p.  Update call to new_strinfo.
	(adjust_related_strinfos): Update after above changes to strinfo.
	Copy full_string_p from origsi.
	(adjust_last_stmt): Use zero_length_string_p.
	(handle_builtin_strlen): Update after above changes to strinfo and
	new_strinfo.  Install the lhs as the string length if the previous
	entry didn't describe a full string.
	(handle_builtin_strchr): Update after above changes to strinfo
	and new_strinfo.
	(handle_builtin_strcpy): Likewise.
	(handle_builtin_strcat): Likewise.
	(handle_builtin_malloc): Likewise.
	(handle_pointer_plus): Likewise.
	(handle_builtin_memcpy): Likewise.  Track nonzero characters
	that aren't necessarily followed by a nul terminator.
	(handle_char_store): Likewise.

gcc/testsuite/
	* gcc.dg/strlenopt-32.c: New testcase.
	* gcc.dg/strlenopt-33.c: Likewise.
	* gcc.dg/strlenopt-33g.c: Likewise.
	* gcc.dg/strlenopt-34.c: Likewise.
	* gcc.dg/strlenopt-35.c: Likewise.

From-SVN: r249880

gcc/ChangeLog

 2017-07-02  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	* tree-ssa-strlen.c (strinfo): Rename the length field to
+	nonzero_chars.  Add a full_string_p field.
+	(compare_nonzero_chars, zero_length_string_p): New functions.
+	(get_addr_stridx): Add an offset_out parameter.
+	Use compare_nonzero_chars.
+	(get_stridx): Update accordingly.  Use compare_nonzero_chars.
+	(new_strinfo): Update after above changes to strinfo.
+	(set_endptr_and_length): Set full_string_p.
+	(get_string_length): Update after above changes to strinfo.
+	(unshare_strinfo): Update call to new_strinfo.
+	(maybe_invalidate): Likewise.
+	(get_stridx_plus_constant): Change off to unsigned HOST_WIDE_INT.
+	Use compare_nonzero_chars and zero_string_p.  Treat nonzero_chars
+	as a uhwi instead of an shwi.  Update after above changes to
+	strinfo and new_strinfo.
+	(zero_length_string): Assert that chainsi contains full strings.
+	Use zero_length_string_p.  Update call to new_strinfo.
+	(adjust_related_strinfos): Update after above changes to strinfo.
+	Copy full_string_p from origsi.
+	(adjust_last_stmt): Use zero_length_string_p.
+	(handle_builtin_strlen): Update after above changes to strinfo and
+	new_strinfo.  Install the lhs as the string length if the previous
+	entry didn't describe a full string.
+	(handle_builtin_strchr): Update after above changes to strinfo
+	and new_strinfo.
+	(handle_builtin_strcpy): Likewise.
+	(handle_builtin_strcat): Likewise.
+	(handle_builtin_malloc): Likewise.
+	(handle_pointer_plus): Likewise.
+	(handle_builtin_memcpy): Likewise.  Track nonzero characters
+	that aren't necessarily followed by a nul terminator.
+	(handle_char_store): Likewise.
+
+2017-07-02  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	PR tree-optimization/80769
 	* tree-ssa-strlen.c (strinfo): Document that "stmt" is also used
 	for malloc and calloc.  Document the new invariant that all related

gcc/testsuite/ChangeLog

 2017-07-02  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	* gcc.dg/strlenopt-32.c: New testcase.
+	* gcc.dg/strlenopt-33.c: Likewise.
+	* gcc.dg/strlenopt-33g.c: Likewise.
+	* gcc.dg/strlenopt-34.c: Likewise.
+	* gcc.dg/strlenopt-35.c: Likewise.
+
+2017-07-02  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	PR tree-optimization/80769
 	* gcc.dg/strlenopt-31.c: New test.
 	* gcc.dg/strlenopt-31g.c: Likewise.

gcc/testsuite/gcc.dg/strlenopt-32.c

+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+char temp[30];
+volatile int v;
+
+size_t __attribute__ ((noinline, noclone))
+f1 (void)
+{
+  char a[30];
+  v += 1;
+  memcpy (a, "1234567", 7);
+  memcpy (a + 7, "89abcdefg", 9);
+  memcpy (a + 16, "h", 2);
+  return strlen (a);	// This strlen should be optimized into 17.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f2 (char *a)
+{
+  v += 2;
+  memcpy (a, "1234567", 7);
+  memcpy (a + 7, "89abcdefg", 9);
+  memcpy (a + 16, "h", 2);
+  return strlen (a);	// This strlen should be optimized into 17.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f3 (void)
+{
+  char a[30];
+  v += 3;
+  a[0] = '1';
+  memcpy (a + 1, "2345678", 8);
+  return strlen (a);	// This strlen should be optimized into 8.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f4 (char *a)
+{
+  v += 4;
+  a[0] = '1';
+  memcpy (a + 1, "2345678", 8);
+  return strlen (a);	// This strlen should be optimized into 8.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f5 (void)
+{
+  char a[30];
+  v += 5;
+  a[0] = '1';
+  a[1] = '2';
+  a[2] = '3';
+  memcpy (a + 3, "456", 3);
+  a[6] = '7';
+  a[7] = 0;
+  return strlen (a);	// This strlen should be optimized into 7.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f6 (char *a)
+{
+  v += 6;
+  a[0] = '1';
+  a[1] = '2';
+  a[2] = '3';
+  memcpy (a + 3, "456", 3);
+  a[6] = '7';
+  a[7] = 0;
+  return strlen (a);	// This strlen should be optimized into 7.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f7 (void)
+{
+  char a[30];
+  v += 7;
+  strcpy (a, "abcde");
+  int len1 = strlen (a);
+  a[2] = '_';
+  int len2 = strlen (a);
+  return len1 + len2;	// This should be optimized into 10.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f8 (char *a)
+{
+  v += 8;
+  strcpy (a, "abcde");
+  int len1 = strlen (a);
+  a[2] = '_';
+  int len2 = strlen (a);
+  return len1 + len2;	// This should be optimized into 10.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f9 (char b)
+{
+  char a[30];
+  v += 9;
+  strcpy (a, "foo.bar");
+  a[4] = b;
+  a[3] = 0;
+  return strlen (a);	// This should be optimized into 3.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f10 (char *a, char b)
+{
+  v += 10;
+  strcpy (a, "foo.bar");
+  a[4] = b;
+  a[3] = 0;
+  return strlen (a);	// This should be optimized into 3.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f11 (void)
+{
+  char a[30];
+  v += 11;
+  strcpy (temp, "123456");
+  memcpy (a, temp, 7);
+  return strlen (a);	// This should be optimized into 6.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f12 (char *a)
+{
+  v += 12;
+  strcpy (temp, "123456");
+  memcpy (a, temp, 7);
+  return strlen (a);	// This should be optimized into 6.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f13 (void)
+{
+  char a[30];
+  v += 13;
+  strcpy (temp, "1234567");
+  memcpy (a, temp, 7);
+  a[7] = 0;
+  return strlen (a);	// This should be optimized into 7.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f14 (char *a)
+{
+  v += 14;
+  strcpy (temp, "1234567");
+  memcpy (a, temp, 7);
+  a[7] = 0;
+  return strlen (a);	// This should be optimized into 7.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f15 (void)
+{
+  char a[30];
+  v += 15;
+  strcpy (temp, "12345679");
+  memcpy (a, temp, 7);
+  a[7] = 0;
+  return strlen (a);	// This should be optimized into 7.
+}
+
+size_t __attribute__ ((noinline, noclone))
+f16 (char *a)
+{
+  v += 16;
+  strcpy (temp, "123456789");
+  memcpy (a, temp, 7);
+  a[7] = 0;
+  return strlen (a);	// This should be optimized into 7.
+}
+
+int
+main ()
+{
+  char a[30];
+  if (f1 () != 17 || f2 (a) != 17 || f3 () != 8 || f4 (a) != 8
+      || f5 () != 7 || f6 (a) != 7 || f7 () != 10 || f8 (a) != 10
+      || f9 ('_') != 3 || f10 (a, '_') != 3 || f11 () != 6 || f12 (a) != 6
+      || f13 () != 7 || f14 (a) != 7 || f15 () != 7 || f16 (a) != 7)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 0 "strlen" } } */

gcc/testsuite/gcc.dg/strlenopt-33.c

+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+volatile int v;
+
+size_t __attribute__ ((noinline, noclone))
+f1 (char *b)
+{
+  char a[30];
+  v += 1;
+  strcpy (a, b);
+  // This needs to stay.
+  int len1 = strlen (a);
+  a[0] = '_';
+  a[1] = 0;
+  return len1 + strlen (a);
+}
+
+size_t __attribute__ ((noinline, noclone))
+f2 (char *a, char *b)
+{
+  v += 2;
+  strcpy (a, b);
+  // This needs to stay.
+  int len1 = strlen (a);
+  a[0] = '_';
+  a[1] = 0;
+  return len1 + strlen (a);
+}
+
+int
+main ()
+{
+  char a[30];
+  if (f1 ("foo") != 4 || f2 (a, "foobar") != 7)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */

gcc/testsuite/gcc.dg/strlenopt-33g.c

+/* { dg-do run { target *-*-linux* *-*-gnu* } } */
+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#define USE_GNU
+#include "strlenopt.h"
+
+volatile int v;
+
+size_t __attribute__ ((noinline, noclone))
+f1 (char *b)
+{
+  char a[30];
+  v += 1;
+  // Should be converted to stpcpy.
+  strcpy (a, b);
+  int len1 = strlen (a);
+  a[0] = '_';
+  a[1] = 0;
+  return len1 + strlen (a);
+}
+
+size_t __attribute__ ((noinline, noclone))
+f2 (char *a, char *b)
+{
+  v += 2;
+  // Should be converted to stpcpy.
+  strcpy (a, b);
+  int len1 = strlen (a);
+  a[0] = '_';
+  a[1] = 0;
+  return len1 + strlen (a);
+}
+
+int
+main ()
+{
+  char a[30];
+  if (f1 ("foo") != 4 || f2 (a, "foobar") != 7)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 0 "strlen" } } */
+/* { dg-final { scan-tree-dump-times "stpcpy \\(" 2 "strlen" } } */

gcc/testsuite/gcc.dg/strlenopt-34.c

+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+volatile int v;
+
+size_t __attribute__ ((noinline, noclone))
+f1 (char b)
+{
+  char a[30];
+  v += 1;
+  strcpy (a, "foo.bar");
+  a[3] = b;
+  a[4] = 0;
+  return strlen (a);
+}
+
+size_t __attribute__ ((noinline, noclone))
+f2 (char *a, char b)
+{
+  v += 2;
+  strcpy (a, "foo.bar");
+  a[3] = b;
+  a[4] = 0;
+  return strlen (a);
+}
+
+int
+main ()
+{
+  char a[30];
+  if (f1 ('_') != 4 || f1 (0) != 3 || f2 (a, '_') != 4 || f2 (a, 0) != 3)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */

gcc/testsuite/gcc.dg/strlenopt-35.c

+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+volatile int v;
+
+size_t
+f1 (char *a1)
+{
+  v += 1;
+  size_t x = strlen (a1);
+  char *a2 = a1 + x;
+  a2[0] = '1';
+  a2[1] = '2';
+  a2[2] = '3';
+  a2[3] = 0;
+  return strlen (a1);
+}
+
+int
+main ()
+{
+  char a[30];
+  strcpy (a, "abcd");
+  if (f1 (a) != 7)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 1 "strlen" } } */