1 files changed, 15 insertions, 7 deletions

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index 3c6bf725e1c..020847afdce 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -167,7 +167,7 @@ static GTY ((if_marked ("ggc_marked_p"), param_is (struct rtx_def)))
 
 static rtx make_call_insn_raw (rtx);
 static rtx change_address_1 (rtx, enum machine_mode, rtx, int);
-static void reset_used_decls (tree);
+static void set_used_decls (tree);
 static void mark_label_nuses (rtx);
 static hashval_t const_int_htab_hash (const void *);
 static int const_int_htab_eq (const void *, const void *);
@@ -2160,11 +2160,11 @@ unshare_all_rtl_again (rtx insn)
       }
 
   /* Make sure that virtual stack slots are not shared.  */
-  reset_used_decls (DECL_INITIAL (cfun->decl));
+  set_used_decls (DECL_INITIAL (cfun->decl));
 
   /* Make sure that virtual parameters are not shared.  */
   for (decl = DECL_ARGUMENTS (cfun->decl); decl; decl = TREE_CHAIN (decl))
-    reset_used_flags (DECL_RTL (decl));
+    set_used_flags (DECL_RTL (decl));
 
   reset_used_flags (stack_slot_list);
 
@@ -2353,20 +2353,28 @@ unshare_all_rtl_in_chain (rtx insn)
 }
 
 /* Go through all virtual stack slots of a function and mark them as
-   not shared.  */
+   shared.  We never replace the DECL_RTLs themselves with a copy,
+   but expressions mentioned into a DECL_RTL cannot be shared with
+   expressions in the instruction stream.
+
+   Note that reload may convert pseudo registers into memories in-place.
+   Pseudo registers are always shared, but MEMs never are.  Thus if we
+   reset the used flags on MEMs in the instruction stream, we must set
+   them again on MEMs that appear in DECL_RTLs.  */
+
 static void
-reset_used_decls (tree blk)
+set_used_decls (tree blk)
 {
   tree t;
 
   /* Mark decls.  */
   for (t = BLOCK_VARS (blk); t; t = TREE_CHAIN (t))
     if (DECL_RTL_SET_P (t))
-      reset_used_flags (DECL_RTL (t));
+      set_used_flags (DECL_RTL (t));
 
   /* Now process sub-blocks.  */
   for (t = BLOCK_SUBBLOCKS (blk); t; t = TREE_CHAIN (t))
-    reset_used_decls (t);
+    set_used_decls (t);
 }
 
 /* Mark ORIG as in use, and return a copy of it if it was already in use.