[gcc(refs/users/guojiufu/heads/guojiufu-branch)] tree-optimization: Fix use of uninitialized variables warnings [PR94952]

[Jiu Fu Guo]

https://gcc.gnu.org/g:2c832ffedf06ff614fc36c44ab6c892d84075e08

commit 2c832ffedf06ff614fc36c44ab6c892d84075e08
Author: Stefan Schulze Frielinghaus <stefansf@linux.ibm.com>
Date:   Tue May 5 19:44:19 2020 +0200

    tree-optimization: Fix use of uninitialized variables warnings [PR94952]
    
    While bootstrapping GCC on S/390 with --enable-checking=release several
    warnings about use of uninitialized variables bitpos, bitregion_start, and
    bitregion_end of function pass_store_merging::process_store are raised.
    According to PR94952 these seem to be false positives which are silenced by
    initialising the mentioned variables.
    
    Bootstrapped on S/390.  Ok for master and releases/gcc-10 assuming that
    regtest succeeds (still running but I don't see a reason why it
    should fail)?
    
    gcc/ChangeLog:
    
    2020-05-18  Stefan Schulze Frielinghaus  <stefansf@linux.ibm.com>
    
            PR tree-optimization/94952
            * gimple-ssa-store-merging.c (pass_store_merging::process_store):
            Initialize variables bitpos, bitregion_start, and bitregion_end in
            order to silence warnings about use of uninitialized variables.

Diff:
---
 gcc/ChangeLog                  | 7 +++++++
 gcc/gimple-ssa-store-merging.c | 4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 51b5b6c908d..0a1ff053ffa 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2020-05-18  Stefan Schulze Frielinghaus  <stefansf@linux.ibm.com>
+
+	PR tree-optimization/94952
+	* gimple-ssa-store-merging.c (pass_store_merging::process_store):
+	Initialize variables bitpos, bitregion_start, and bitregion_end in
+	order to silence warnings about use of uninitialized variables.
+
 2020-05-18  Carl Love  <cel@us.ibm.com>
 
 	PR target/94833
diff --git a/gcc/gimple-ssa-store-merging.c b/gcc/gimple-ssa-store-merging.c
index 25753517cc6..c8e1877f540 100644
--- a/gcc/gimple-ssa-store-merging.c
+++ b/gcc/gimple-ssa-store-merging.c
@@ -4668,8 +4668,8 @@ pass_store_merging::process_store (gimple *stmt)
 {
   tree lhs = gimple_assign_lhs (stmt);
   tree rhs = gimple_assign_rhs1 (stmt);
-  poly_uint64 bitsize, bitpos;
-  poly_uint64 bitregion_start, bitregion_end;
+  poly_uint64 bitsize, bitpos = 0;
+  poly_uint64 bitregion_start = 0, bitregion_end = 0;
   tree base_addr
     = mem_valid_for_store_merging (lhs, &bitsize, &bitpos,
 				   &bitregion_start, &bitregion_end);