PR tree-optimization/92683 - strncmp incorrect result with equal substrings and non-const bound

gcc/testsuite/ChangeLog:

	PR tree-optimization/92683
	* gcc.dg/strcmpopt_8.c: New test.
	* gcc.dg/strcmpopt_9.c: New test.

gcc/ChangeLog:

	PR tree-optimization/92683
	* gimple-fold.c (gimple_fold_builtin_string_compare): Restore a test
	inadvertently removed in a previous change.  Rename local variable
	for clarity.

From-SVN: r278742

5 files changed, 233 insertions, 5 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 35dcc4e..205c489 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2019-11-26  Martin Sebor  <msebor@redhat.com>
+
+	PR tree-optimization/92683
+	* gimple-fold.c (gimple_fold_builtin_string_compare): Restore a test
+	inadvertently removed in a previous change.  Rename local variable
+	for clarity.
+
 2019-11-26  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/92669
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index fadc422..849bee2 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -2346,18 +2346,19 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi)
   tree str1 = gimple_call_arg (stmt, 0);
   tree str2 = gimple_call_arg (stmt, 1);
   tree lhs = gimple_call_lhs (stmt);
-  tree len = NULL_TREE;
+
+  tree bound_node = NULL_TREE;
   unsigned HOST_WIDE_INT bound = HOST_WIDE_INT_M1U;
 
   /* Handle strncmp and strncasecmp functions.  */
   if (gimple_call_num_args (stmt) == 3)
     {
-      len = gimple_call_arg (stmt, 2);
-      if (tree_fits_uhwi_p (len))
-	bound = tree_to_uhwi (len);
+      bound_node = gimple_call_arg (stmt, 2);
+      if (tree_fits_uhwi_p (bound_node))
+	bound = tree_to_uhwi (bound_node);
     }
 
-  /* If the LEN parameter is zero, return zero.  */
+  /* If the BOUND parameter is zero, return zero.  */
   if (bound == 0)
     {
       replace_call_with_value (gsi, integer_zero_node);
@@ -2418,6 +2419,9 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi)
 	case BUILT_IN_STRNCMP:
 	case BUILT_IN_STRNCMP_EQ:
 	  {
+	    if (bound == HOST_WIDE_INT_M1U)
+	      break;
+
 	    /* Reduce the bound to be no more than the length
 	       of the shorter of the two strings, or the sizes
 	       of the unterminated arrays.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a8926cc..4dd9b7f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2019-11-26  Martin Sebor  <msebor@redhat.com>
+
+	PR tree-optimization/92683
+	* gcc.dg/strcmpopt_8.c: New test.
+	* gcc.dg/strcmpopt_9.c: New test.
+
 2019-11-26  Joel Hutton  <Joel.Hutton@arm.com>
 
 	PR testsuite/92391
diff --git a/gcc/testsuite/gcc.dg/strcmpopt_8.c b/gcc/testsuite/gcc.dg/strcmpopt_8.c
new file mode 100644
index 0000000..a90c0d3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/strcmpopt_8.c
@@ -0,0 +1,177 @@
+/* PR tree-optimization/92683 - strncmp incorrect result with equal substrings
+   and nonconst bound
+   { dg-do compile }
+   { dg-options "-O1 -Wall -fdump-tree-forwprop1" } */
+
+#define SIZE_MAX  __SIZE_MAX__
+
+#define S123  "123"
+#define S1234 "1234"
+
+typedef __SIZE_TYPE__ size_t;
+
+#ifndef ident
+#  define ident(n) n
+#endif
+
+extern void failure_on_line (int);
+
+/* Verify that the test in 'if (EQL strncmp (S, T, N))' is folded.  */
+#define T(eql, s, t, n) do {			\
+    max = ident (n);				\
+    if (!(eql __builtin_strncmp (s, t, max)))	\
+      failure_on_line (__LINE__);		\
+  } while (0)
+
+void test_literal (void)
+{
+  size_t max;
+
+  T (0 ==, S123, S1234, 0);
+  T (0 ==, S123, S1234, 1);
+  T (0 ==, S123, S1234, 2);
+  T (0 ==, S123, S1234, 3);
+  T (0 >,  S123, S1234, 4);
+  T (0 >,  S123, S1234, 5);
+  T (0 >,  S123, S1234, SIZE_MAX - 2);
+  T (0 >,  S123, S1234, SIZE_MAX - 1);
+  T (0 >,  S123, S1234, SIZE_MAX);
+
+  T (0 ==, S123 + 1, S1234, 0);
+  T (0 <,  S123 + 1, S1234, 1);
+  T (0 <,  S123 + 1, S1234, 2);
+  T (0 <,  S123 + 1, S1234, 3);
+  T (0 <,  S123 + 1, S1234, 4);
+  T (0 <,  S123 + 1, S1234, SIZE_MAX - 2);
+  T (0 <,  S123 + 1, S1234, SIZE_MAX - 1);
+  T (0 <,  S123 + 1, S1234, SIZE_MAX);
+
+  T (0 ==, S123 + 1, S1234 + 1, 0);
+  T (0 ==, S123 + 1, S1234 + 1, 1);
+  T (0 ==, S123 + 1, S1234 + 1, 2);
+  T (0 >,  S123 + 1, S1234 + 1, 3);
+  T (0 >,  S123 + 1, S1234 + 1, SIZE_MAX - 1);
+  T (0 >,  S123 + 1, S1234 + 1, SIZE_MAX);
+
+  T (0 ==, S123 + 3, S1234 + 1, 0);
+  T (0 >,  S123 + 3, S1234 + 1, 1);
+  T (0 >,  S123 + 3, S1234 + 1, 2);
+  T (0 >,  S123 + 3, S1234 + 1, 3);
+  T (0 >,  S123 + 3, S1234 + 1, SIZE_MAX - 1);
+  T (0 >,  S123 + 3, S1234 + 1, SIZE_MAX);
+
+  int zero = 0;
+
+  T (zero ==, S123, S1234, 0);
+  T (zero ==, S123, S1234, 1);
+  T (zero ==, S123, S1234, 2);
+  T (zero ==, S123, S1234, 3);
+  T (zero >,  S123, S1234, 4);
+  T (zero >,  S123, S1234, 5);
+  T (zero >,  S123, S1234, SIZE_MAX - 2);
+  T (zero >,  S123, S1234, SIZE_MAX - 1);
+  T (zero >,  S123, S1234, SIZE_MAX);
+
+  T (zero ==, S123 + 1, S1234, 0);
+  T (zero <,  S123 + 1, S1234, 1);
+  T (zero <,  S123 + 1, S1234, 2);
+  T (zero <,  S123 + 1, S1234, 3);
+  T (zero <,  S123 + 1, S1234, 4);
+  T (zero <,  S123 + 1, S1234, SIZE_MAX - 2);
+  T (zero <,  S123 + 1, S1234, SIZE_MAX - 1);
+  T (zero <,  S123 + 1, S1234, SIZE_MAX);
+
+  T (zero ==, S123 + 1, S1234 + 1, 0);
+  T (zero ==, S123 + 1, S1234 + 1, 1);
+  T (zero ==, S123 + 1, S1234 + 1, 2);
+  T (zero >,  S123 + 1, S1234 + 1, 3);
+  T (zero >,  S123 + 1, S1234 + 1, SIZE_MAX - 1);
+  T (zero >,  S123 + 1, S1234 + 1, SIZE_MAX);
+
+  T (zero ==, S123 + 3, S1234 + 1, 0);
+  T (zero >,  S123 + 3, S1234 + 1, 1);
+  T (zero >,  S123 + 3, S1234 + 1, 2);
+  T (zero >,  S123 + 3, S1234 + 1, 3);
+  T (zero >,  S123 + 3, S1234 + 1, SIZE_MAX - 1);
+  T (zero >,  S123 + 3, S1234 + 1, SIZE_MAX);
+}
+
+const char s123[] = S123;
+const char s1234[] = S1234;
+
+void test_cst_array (void)
+{
+  size_t max;
+
+  T (0 ==, s123, s1234, 0);
+  T (0 ==, s123, s1234, 1);
+  T (0 ==, s123, s1234, 2);
+  T (0 ==, s123, s1234, 3);
+  T (0 >,  s123, s1234, 4);
+  T (0 >,  s123, s1234, 5);
+  T (0 >,  s123, s1234, SIZE_MAX - 2);
+  T (0 >,  s123, s1234, SIZE_MAX - 1);
+  T (0 >,  s123, s1234, SIZE_MAX);
+
+  T (0 ==, s123 + 1, s1234, 0);
+  T (0 <,  s123 + 1, s1234, 1);
+  T (0 <,  s123 + 1, s1234, 2);
+  T (0 <,  s123 + 1, s1234, 3);
+  T (0 <,  s123 + 1, s1234, 4);
+  T (0 <,  s123 + 1, s1234, SIZE_MAX - 2);
+  T (0 <,  s123 + 1, s1234, SIZE_MAX - 1);
+  T (0 <,  s123 + 1, s1234, SIZE_MAX);
+
+  T (0 ==, s123 + 1, s1234 + 1, 0);
+  T (0 ==, s123 + 1, s1234 + 1, 1);
+  T (0 ==, s123 + 1, s1234 + 1, 2);
+  T (0 >,  s123 + 1, s1234 + 1, 3);
+  T (0 >,  s123 + 1, s1234 + 1, SIZE_MAX - 1);
+  T (0 >,  s123 + 1, s1234 + 1, SIZE_MAX);
+
+  T (0 ==, s123 + 3, s1234 + 1, 0);
+  T (0 >,  s123 + 3, s1234 + 1, 1);
+  T (0 >,  s123 + 3, s1234 + 1, 2);
+  T (0 >,  s123 + 3, s1234 + 1, 3);
+  T (0 >,  s123 + 3, s1234 + 1, SIZE_MAX - 1);
+  T (0 >,  s123 + 3, s1234 + 1, SIZE_MAX);
+
+  int zero = 0;
+
+  T (zero ==, s123, s1234, 0);
+  T (zero ==, s123, s1234, 1);
+  T (zero ==, s123, s1234, 2);
+  T (zero ==, s123, s1234, 3);
+  T (zero >,  s123, s1234, 4);
+  T (zero >,  s123, s1234, 5);
+  T (zero >,  s123, s1234, SIZE_MAX - 2);
+  T (zero >,  s123, s1234, SIZE_MAX - 1);
+  T (zero >,  s123, s1234, SIZE_MAX);
+
+  T (zero ==, s123 + 1, s1234, 0);
+  T (zero <,  s123 + 1, s1234, 1);
+  T (zero <,  s123 + 1, s1234, 2);
+  T (zero <,  s123 + 1, s1234, 3);
+  T (zero <,  s123 + 1, s1234, 4);
+  T (zero <,  s123 + 1, s1234, SIZE_MAX - 2);
+  T (zero <,  s123 + 1, s1234, SIZE_MAX - 1);
+  T (zero <,  s123 + 1, s1234, SIZE_MAX);
+
+  T (zero ==, s123 + 1, s1234 + 1, 0);
+  T (zero ==, s123 + 1, s1234 + 1, 1);
+  T (zero ==, s123 + 1, s1234 + 1, 2);
+  T (zero >,  s123 + 1, s1234 + 1, 3);
+  T (zero >,  s123 + 1, s1234 + 1, SIZE_MAX - 1);
+  T (zero >,  s123 + 1, s1234 + 1, SIZE_MAX);
+
+  T (zero ==, s123 + 3, s1234 + 1, 0);
+  T (zero >,  s123 + 3, s1234 + 1, 1);
+  T (zero >,  s123 + 3, s1234 + 1, 2);
+  T (zero >,  s123 + 3, s1234 + 1, 3);
+  T (zero >,  s123 + 3, s1234 + 1, SIZE_MAX - 1);
+  T (zero >,  s123 + 3, s1234 + 1, SIZE_MAX);
+}
+
+/* { dg-final { scan-tree-dump-not "strcmp" "forwprop1" } }
+   { dg-final { scan-tree-dump-not "strncmp" "forwprop1" } }
+   { dg-final { scan-tree-dump-not "failure_on_line_" "forwprop1" } } */
diff --git a/gcc/testsuite/gcc.dg/strcmpopt_9.c b/gcc/testsuite/gcc.dg/strcmpopt_9.c
new file mode 100644
index 0000000..15f6b63
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/strcmpopt_9.c
@@ -0,0 +1,34 @@
+/* PR tree-optimization/92683 - strncmp incorrect result with equal substrings
+   and nonconst bound
+   { dg-do run }
+   { dg-options "-O2 -Wall" } */
+
+#include "strlenopt.h"
+
+#define ident(n) ident (n)
+
+__attribute__ ((noclone, noinline, noipa)) size_t
+ident (size_t x)
+{
+  return x;
+}
+
+int nfails;
+
+__attribute__ ((noclone, noinline, noipa)) void
+failure_on_line (int line)
+{
+  __builtin_printf ("failure on line %i\n", line);
+  ++nfails;
+}
+
+#include "strcmpopt_8.c"
+
+int main (void)
+{
+  test_literal ();
+  test_cst_array ();
+
+  if (nfails)
+    __builtin_abort ();
+}