[PATCH] PR91195: fix -Wmaybe-uninitialized warning for conditional store optimization

[JiangNing OS]

This patch is to fix PR91195. Is it OK for trunk?

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 711a31ea597..4db36644160 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2019-07-22  Jiangning Liu  <jiangning....@amperecomputing.com>
+
+       PR middle-end/91195
+       * tree-ssa-phiopt.c (cond_store_replacement): Work around
+       -Wmaybe-uninitialized warning.
+
 2019-07-22  Stafford Horne  <sho...@gmail.com>
 
        * config/or1k/or1k.c (or1k_expand_compare): Check for int before
diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
index b64bde695f4..7a86007d087 100644
--- a/gcc/tree-ssa-phiopt.c
+++ b/gcc/tree-ssa-phiopt.c
@@ -2240,6 +2240,14 @@ cond_store_replacement (basic_block middle_bb, 
basic_block join_bb,
       tree base = get_base_address (lhs);
       if (!auto_var_p (base) || TREE_ADDRESSABLE (base))
        return false;
+
+      /* The transformation below will inherently introduce a memory load,
+        for which LHS may not be initialized yet if it is not in NOTRAP,
+        so a -Wmaybe-uninitialized warning message could be triggered.
+        Since it's a bit hard to have a very accurate uninitialization
+        analysis to memory reference, we disable the warning here to avoid
+        confusion.  */
+      TREE_NO_WARNING (lhs) = 1;
     }
 
   /* Now we've checked the constraints, so do the transformation:

Thanks,
-Jiangning