[gcc r13-2258] middle-end: intialize regnum in store_bit_field_1

[Tamar Christina <tnfchris@gcc.gnu.org>]

https://gcc.gnu.org/g:368dbb23c5efaf86b2b18945508d379713c0d12c

commit r13-2258-g368dbb23c5efaf86b2b18945508d379713c0d12c
Author: Tamar Christina <tamar.christina@arm.com>
Date:   Tue Aug 30 07:48:21 2022 +0100

    middle-end: intialize regnum in store_bit_field_1
    
    This initializes regnum to 0 for when undefined_p.
    0 is the right default as it's supposed to get the lowpart
    when undefined.
    
    gcc/ChangeLog:
    
            * expmed.cc (store_bit_field_1): Initialize regnum to 0.

Diff:
---
 gcc/expmed.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/expmed.cc b/gcc/expmed.cc
index 8d7418be418..cdc0adb3892 100644
--- a/gcc/expmed.cc
+++ b/gcc/expmed.cc
@@ -794,7 +794,7 @@ store_bit_field_1 (rtx str_rtx, poly_uint64 bitsize, poly_uint64 bitnum,
 	 words or to cope with mode punning between equal-sized modes.
 	 In the latter case, use subreg on the rhs side, not lhs.  */
       rtx sub;
-      HOST_WIDE_INT regnum;
+      HOST_WIDE_INT regnum = 0;
       poly_uint64 regsize = REGMODE_NATURAL_SIZE (GET_MODE (op0));
       if (known_eq (bitnum, 0U)
 	  && known_eq (bitsize, GET_MODE_BITSIZE (GET_MODE (op0))))