cfgcleanup: Ignore clobbers in bb_is_just_return

The function bb_is_just_return finds if the BB it is asked about does
just a return and nothing else.  It currently does not allow clobbers
in the block either, which we of course can allow just fine.

This patch changes that.


	* cfgcleanup.c (bb_is_just_return): Allow CLOBBERs.

gcc/testsuite/

From-SVN: r248351

gcc/ChangeLog

+2017-05-22  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* cfgcleanup.c (bb_is_just_return): Allow CLOBBERs.
+
 2017-05-22  Jakub Jelinek  <jakub@redhat.com>
 
 	PR middle-end/80809

gcc/cfgcleanup.c

@@ -2666,7 +2666,7 @@ trivially_empty_bb_p (basic_block bb)
 
 /* Return true if BB contains just a return and possibly a USE of the
    return value.  Fill in *RET and *USE with the return and use insns
-   if any found, otherwise NULL.  */
+   if any found, otherwise NULL.  All CLOBBERs are ignored.  */
 
 static bool
 bb_is_just_return (basic_block bb, rtx_insn **ret, rtx_insn **use)
@@ -2680,13 +2680,15 @@ bb_is_just_return (basic_block bb, rtx_insn **ret, rtx_insn **use)
   FOR_BB_INSNS (bb, insn)
     if (NONDEBUG_INSN_P (insn))
       {
-	if (!*ret && ANY_RETURN_P (PATTERN (insn)))
+	rtx pat = PATTERN (insn);
+
+	if (!*ret && ANY_RETURN_P (pat))
 	  *ret = insn;
-	else if (!*ret && !*use && GET_CODE (PATTERN (insn)) == USE
-	    && REG_P (XEXP (PATTERN (insn), 0))
-	    && REG_FUNCTION_VALUE_P (XEXP (PATTERN (insn), 0)))
+	else if (!*ret && !*use && GET_CODE (pat) == USE
+	    && REG_P (XEXP (pat, 0))
+	    && REG_FUNCTION_VALUE_P (XEXP (pat, 0)))
 	  *use = insn;
-	else
+	else if (GET_CODE (pat) != CLOBBER)
 	  return false;
       }
 

gcc/testsuite/ChangeLog

+2017-05-22  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* gcc.target/powerpc/conditional-return.c: New testcase.
+
 2017-05-22  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
 
 	* gcc.target/powerpc/p8-vec-xl-xst.c: Fix target string to

gcc/testsuite/gcc.target/powerpc/conditional-return.c

+/* Check that a conditional return is used.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -w" } */
+
+/* { dg-final { scan-assembler {\mbeqlr\M} } } */
+
+
+int f(int x)
+{
+	if (x)
+		return x + 31;
+
+	return;
+}