[Patch, rs6000] Call library for block memory compare when optimizing for size

[HAO CHEN GUI]

Hi,
  This patch call library function for block memory compare when it's
optimized for size.

  Bootstrapped and tested on x86 and powerpc64-linux BE and LE with no
regressions. Is this OK for trunk?

Thanks
Gui Haochen

ChangeLog
rs6000: Call library for block memory compare when optimizing for size

gcc/
        * config/rs6000/rs6000-string.cc (expand_block_compare): Return
        false when optimizing for size.

gcc/testsuite/
        * gcc.target/powerpc/block-cm-3.c: New.

patch.diff
diff --git a/gcc/config/rs6000/rs6000-string.cc 
b/gcc/config/rs6000/rs6000-string.cc
index 05dc41622f4..5149273b80e 100644
--- a/gcc/config/rs6000/rs6000-string.cc
+++ b/gcc/config/rs6000/rs6000-string.cc
@@ -1947,6 +1947,9 @@ expand_block_compare_gpr(unsigned HOST_WIDE_INT bytes, 
unsigned int base_align,
 bool
 expand_block_compare (rtx operands[])
 {
+  if (optimize_insn_for_size_p ())
+    return false;
+
   rtx target = operands[0];
   rtx orig_src1 = operands[1];
   rtx orig_src2 = operands[2];
diff --git a/gcc/testsuite/gcc.target/powerpc/block-cmp-3.c 
b/gcc/testsuite/gcc.target/powerpc/block-cmp-3.c
new file mode 100644
index 00000000000..c7e853ad593
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/block-cmp-3.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-final { scan-assembler-times {\mb[l]? memcmp\M} 1 } }  */
+
+int foo (const char* s1, const char* s2)
+{
+  return __builtin_memcmp (s1, s2, 4);
+}