gimple-fold: Use ranges to simplify strncat and snprintf

Use ranges for lengths and object sizes in strncat and snprintf to
determine if they can be transformed into simpler operations.

gcc/ChangeLog:

	* gimple-fold.c (gimple_fold_builtin_strncat): Use ranges to
	determine if it is safe to transform to strcat.
	(gimple_fold_builtin_snprintf): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.dg/fold-stringops-2.c: Define size_t.
	(safe1): Adjust.
	(safe4): New test.
	* gcc.dg/fold-stringops-3.c: New test.

Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>

2 files changed, 33 insertions, 1 deletions

diff --git a/gcc/testsuite/gcc.dg/fold-stringops-2.c b/gcc/testsuite/gcc.dg/fold-stringops-2.c
index 0b415df..ac7d29e 100644
--- a/gcc/testsuite/gcc.dg/fold-stringops-2.c
+++ b/gcc/testsuite/gcc.dg/fold-stringops-2.c
@@ -1,10 +1,12 @@
 /* { dg-do compile } */
 /* { dg-options "-O2" } */
 
+typedef __SIZE_TYPE__ size_t;
+
 #define bos(__d) __builtin_object_size ((__d), 0)
 
 char *
-safe1 (const char *src, int cond, __SIZE_TYPE__ len)
+safe1 (const char *src, int cond, size_t len)
 {
   char *dst;
 
@@ -44,6 +46,18 @@ safe3 (const char *src, int cond, unsigned char len)
   return __builtin___snprintf_chk (dst, len, 0, bos (dst), "%s", src);
 }
 
+char dst[1024];
+
+void
+safe4 (size_t len)
+{
+  len = len > sizeof (dst) - 1 ? sizeof (dst) - 1 : len;
+  len = len < sizeof (dst) / 2 ? sizeof (dst) / 2 : len;
+
+  __builtin_strncat (dst, "hello", len);
+}
+
 /* { dg-final { scan-assembler-not "__memcpy_chk" } } */
 /* { dg-final { scan-assembler-not "__strncpy_chk" } } */
 /* { dg-final { scan-assembler-not "__snprintf_chk" } } */
+/* { dg-final { scan-assembler-not "strncat" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-stringops-3.c b/gcc/testsuite/gcc.dg/fold-stringops-3.c
new file mode 100644
index 0000000..ae2efbf
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-stringops-3.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+char dst[1024];
+
+void
+safe1 (size_t len)
+{
+  len = len > sizeof (dst) ? sizeof (dst) : len;
+  len = len < sizeof (dst) / 2 ? sizeof (dst) / 2 : len;
+
+  __builtin_snprintf (dst, len, "hello");
+  __builtin_snprintf (dst + 5, len, "%s", " world");
+}
+
+/* { dg-final { scan-assembler-not "snprintf" } } */