Uninitialized padding in struct _dep.

In struct _dep, there is an implicit padding of 4bits.  This
bit-field padding is uninitialized when init_dep_1 is being called.
This means we access uninitialized memory but never use it for
anything.  Adding an unused bit-field field and initializing it
in init_dep_1 will improve code generation also as we initialize
the whole 32bits now rather than just part of it.

ChangeLog:
* sched-int.h (_dep): Add unused bit-field field for the padding.
* sched-deps.c (init_dep_1): Init unused field.

gcc/ChangeLog

@@ -1,3 +1,8 @@
+2020-01-16  Andrew Pinski  <apinski@marvell.com>
+
+	* sched-int.h (_dep): Add unused bit-field field for the padding.
+	* sched-deps.c (init_dep_1): Init unused field.
+
 2020-01-16  Andrew Pinski  <apinski@marvell.com>
 
 	* optabs.h (create_expand_operand): Initialize target field also.

gcc/sched-deps.c

@@ -101,6 +101,7 @@ init_dep_1 (dep_t dep, rtx_insn *pro, rtx_insn *con, enum reg_note type, ds_t ds
   DEP_NONREG (dep) = 0;
   DEP_MULTIPLE (dep) = 0;
   DEP_REPLACE (dep) = NULL;
+  dep->unused = 0;
 }
 
 /* Init DEP with the arguments.

gcc/sched-int.h

@@ -238,6 +238,8 @@ struct _dep
   /* Cached cost of the dependency.  Make sure to update UNKNOWN_DEP_COST
      when changing the size of this field.  */
   int cost:20;
+
+  unsigned unused:4;
 };
 
 #define UNKNOWN_DEP_COST ((int) ((unsigned int) -1 << 19))