[gcc r10-6000] Uninitialized padding in struct _dep.

[Andrew Pinski]

https://gcc.gnu.org/g:7c6056d52ef7ea43b503b11a571b316d55f392c7

commit r10-6000-g7c6056d52ef7ea43b503b11a571b316d55f392c7
Author: Andrew Pinski <apinski@marvell.com>
Date:   Thu Jan 16 02:07:28 2020 +0000

    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:
---
 gcc/ChangeLog    | 5 +++++
 gcc/sched-deps.c | 1 +
 gcc/sched-int.h  | 2 ++
 3 files changed, 8 insertions(+)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4196998..bbb7e06 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,10 @@
 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.
 
 2020-01-16  Andre Vieira  <andre.simoesdiasvieira@arm.com>
diff --git a/gcc/sched-deps.c b/gcc/sched-deps.c
index 9182aba..331af5f 100644
--- 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 833b552..a847f87 100644
--- 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))