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.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4196998ff69bf4c190c7dab09927de0529e3700b..bbb7e06c7fb36f51f6ed3f58ac53183e08e6bac9 100644 (file)
--- a/gcc/ChangeLog
+++ b/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.

diff --git a/gcc/sched-deps.c b/gcc/sched-deps.c
index 9182aba5588cbe5df8848eca2dfdfa33e87e8e7b..331af5ffdb3b6d06d8dd05a68c28ad16d917b32b 100644 (file)
--- a/gcc/sched-deps.c
+++ b/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.

diff --git a/gcc/sched-int.h b/gcc/sched-int.h
index 833b552a340a393f68a1f03cfc20735e0ee3a091..a847f876e65915ca9a7a5d6a2c304b0381471e02 100644 (file)
--- a/gcc/sched-int.h
+++ b/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))