var-tracking.c (vt_stack_adjustments): Don't require stack_adjusts to match for the exit block.

gcc/
	* var-tracking.c (vt_stack_adjustments): Don't require stack_adjusts
	to match for the exit block.

From-SVN: r207602

2 files changed, 24 insertions, 2 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 13fac24..f6e3143 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2014-02-07  Richard Sandiford  <rsandifo@linux.vnet.ibm.com>
+
+	* var-tracking.c (vt_stack_adjustments): Don't require stack_adjusts
+	to match for the exit block.
+
 2014-02-07  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
 
 	* config/s390/s390.md ("atomic_load<mode>", "atomic_store<mode>")
diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c
index a13cac7..c5ce1dd 100644
--- a/gcc/var-tracking.c
+++ b/gcc/var-tracking.c
@@ -886,8 +886,25 @@ vt_stack_adjustments (void)
 	}
       else
 	{
-	  /* Check whether the adjustments on the edges are the same.  */
-	  if (VTI (dest)->in.stack_adjust != VTI (src)->out.stack_adjust)
+	  /* We can end up with different stack adjustments for the exit block
+	     of a shrink-wrapped function if stack_adjust_offset_pre_post
+	     doesn't understand the rtx pattern used to restore the stack
+	     pointer in the epilogue.  For example, on s390(x), the stack
+	     pointer is often restored via a load-multiple instruction
+	     and so no stack_adjust offset is recorded for it.  This means
+	     that the stack offset at the end of the epilogue block is the
+	     the same as the offset before the epilogue, whereas other paths
+	     to the exit block will have the correct stack_adjust.
+
+	     It is safe to ignore these differences because (a) we never
+	     use the stack_adjust for the exit block in this pass and
+	     (b) dwarf2cfi checks whether the CFA notes in a shrink-wrapped
+	     function are correct.
+
+	     We must check whether the adjustments on other edges are
+	     the same though.  */
+	  if (dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
+	      && VTI (dest)->in.stack_adjust != VTI (src)->out.stack_adjust)
 	    {
 	      free (stack);
 	      return false;