* combine.c (reg_nonzero_bits_for_combine): Apply mask transformation

	as applied to nonzero_sign_valid when last_set_mode has less precision
	than mode.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@205550 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 8 insertions, 1 deletions

diff --git a/gcc/combine.c b/gcc/combine.c
index d685a7f6a66..25cf273f808 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -9472,7 +9472,13 @@ reg_nonzero_bits_for_combine (const_rtx x, enum machine_mode mode,
 		  (DF_LR_IN (ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb),
 		   REGNO (x)))))
     {
-      *nonzero &= rsp->last_set_nonzero_bits;
+      unsigned HOST_WIDE_INT mask = rsp->last_set_nonzero_bits;
+
+      if (GET_MODE_PRECISION (rsp->last_set_mode) < GET_MODE_PRECISION (mode))
+	/* We don't know anything about the upper bits.  */
+	mask |= GET_MODE_MASK (mode) ^ GET_MODE_MASK (rsp->last_set_mode);
+
+      *nonzero &= mask;
       return NULL;
     }
 
@@ -9505,6 +9511,7 @@ reg_nonzero_bits_for_combine (const_rtx x, enum machine_mode mode,
       if (GET_MODE_PRECISION (GET_MODE (x)) < GET_MODE_PRECISION (mode))
 	/* We don't know anything about the upper bits.  */
 	mask |= GET_MODE_MASK (mode) ^ GET_MODE_MASK (GET_MODE (x));
+
       *nonzero &= mask;
     }