Disable strcmp/strncmp/memcmp inlining when optimization

level is lower than 2 or Os

From-SVN: r263028

gcc/ChangeLog

+2018-07-26  Qing Zhao  <qing.zhao@oracle.com>
+
+	* builtins.c (inline_expand_builtin_string_cmp): Disable inlining
+	when optimization level is lower than 2 or optimize for size.
+
 2018-07-26  Martin Sebor  <msebor@redhat.com>
 
 	PR tree-optimization/86043

gcc/builtins.c

@@ -6854,6 +6854,11 @@ inline_expand_builtin_string_cmp (tree exp, rtx target)
   unsigned HOST_WIDE_INT length = 0;
   bool is_ncmp = (fcode == BUILT_IN_STRNCMP || fcode == BUILT_IN_MEMCMP);
 
+  /* Do NOT apply this inlining expansion when optimizing for size or 
+     optimization level below 2.  */
+  if (optimize < 2 || optimize_insn_for_size_p ())
+    return NULL_RTX;
+
   gcc_checking_assert (fcode == BUILT_IN_STRCMP
 		       || fcode == BUILT_IN_STRNCMP
 		       || fcode == BUILT_IN_MEMCMP);

gcc/testsuite/ChangeLog

+2018-07-26  Qing Zhao  <qing.zhao@oracle.com>
+
+	* gcc.dg/strcmpopt_5.c: Change to O2 to enable the transformation.
+	* gcc.dg/strcmpopt_6.c: Likewise.
+
 2018-07-26  Pat Haugen  <pthaugen@us.ibm.com>
 
 	PR target/86612

gcc/testsuite/gcc.dg/strcmpopt_5.c

 /* { dg-do run } */
-/* { dg-options "-O -fdump-rtl-expand" } */
+/* { dg-options "-O2 -fdump-rtl-expand" } */
 
 typedef struct { char s[8]; int x; } S;
 __attribute__ ((noinline)) int

gcc/testsuite/gcc.dg/strcmpopt_6.c

 /* When the specified length exceeds one of the arguments of the call to memcmp, 
    the call to memcmp should NOT be inlined.  */
 /* { dg-do run } */
-/* { dg-options "-O -fdump-rtl-expand -Wno-stringop-overflow" } */
+/* { dg-options "-O2 -fdump-rtl-expand -Wno-stringop-overflow" } */
 
 typedef struct { char s[8]; int x; } S;
 
@@ -33,4 +33,4 @@ int main (void)
 
 }
 
-/* { dg-final { scan-rtl-dump-times "__builtin_memcmp" 4 "expand" } } */
+/* { dg-final { scan-rtl-dump-times "__builtin_memcmp" 6 "expand" } } */