0001-Add-TARGET_CLEAR_BY_PIECES.patch

From e45326a4d5c2ea5d60077ac61458c13e5535b76d Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 15 Jul 2021 09:09:15 -0700
Subject: [PATCH] Add TARGET_CLEAR_BY_PIECES

---
 gcc/config/i386/i386.c |  3 +++
 gcc/doc/tm.texi        |  5 +++++
 gcc/doc/tm.texi.in     |  2 ++
 gcc/expr.c             | 12 ++----------
 gcc/target.def         |  7 +++++++
 gcc/targhooks.c        |  8 ++++++++
 gcc/targhooks.h        |  2 ++
 7 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index c0559d50021..d0f53e98acd 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -23729,6 +23729,9 @@ ix86_run_selftests (void)
 #undef TARGET_OVERLAP_OP_BY_PIECES_P
 #define TARGET_OVERLAP_OP_BY_PIECES_P hook_bool_void_true
 
+#undef TARGET_CLEAR_BY_PIECES
+#define TARGET_CLEAR_BY_PIECES builtin_memset_read_str
+
 #undef TARGET_FLAGS_REGNUM
 #define TARGET_FLAGS_REGNUM FLAGS_REG
 #undef TARGET_FIXED_CONDITION_CODE_REGS
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index c1995270720..ad0158c003e 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -6872,6 +6872,11 @@ in the smallest integer mode for the last piece operation of a memory
 region can be generated to avoid doing more than one smaller operations.
 @end deftypefn
 
+@deftypefn {Target Hook} rtx TARGET_CLEAR_BY_PIECES (void *@var{}, void *@var{}, @var{HOST_WIDE_INT}, @var{scalar_int_mode})
+This target hook should return an rtx that is used to clear memory.
+The default returns @code{const0_rtx}.
+@end deftypefn
+
 @deftypefn {Target Hook} int TARGET_COMPARE_BY_PIECES_BRANCH_RATIO (machine_mode @var{mode})
 When expanding a block comparison in MODE, gcc can try to reduce the
 number of branches at the expense of more memory operations.  This hook
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index a6bbf4f2667..b229d49c0d4 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4517,6 +4517,8 @@ If you don't define this, a reasonable default is used.
 
 @hook TARGET_OVERLAP_OP_BY_PIECES_P
 
+@hook TARGET_CLEAR_BY_PIECES
+
 @hook TARGET_COMPARE_BY_PIECES_BRANCH_RATIO
 
 @defmac MOVE_MAX_PIECES
diff --git a/gcc/expr.c b/gcc/expr.c
index 6a4368113c4..68effd3114b 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -1513,15 +1513,6 @@ store_by_pieces (rtx to, unsigned HOST_WIDE_INT len,
     return to;
 }
 
-/* Callback routine for clear_by_pieces.
-   Return const0_rtx unconditionally.  */
-
-static rtx
-clear_by_pieces_1 (void *, void *, HOST_WIDE_INT, scalar_int_mode)
-{
-  return const0_rtx;
-}
-
 /* Generate several move instructions to clear LEN bytes of block TO.  (A MEM
    rtx with BLKmode).  ALIGN is maximum alignment we can assume.  */
 
@@ -1531,7 +1522,8 @@ clear_by_pieces (rtx to, unsigned HOST_WIDE_INT len, unsigned int align)
   if (len == 0)
     return;
 
-  store_by_pieces_d data (to, clear_by_pieces_1, NULL, len, align);
+  char c = 0;
+  store_by_pieces_d data (to, targetm.clear_by_pieces, &c, len, align);
   data.run ();
 }
 
diff --git a/gcc/target.def b/gcc/target.def
index cc4aa3a4212..019e2fa595d 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -3692,6 +3692,13 @@ region can be generated to avoid doing more than one smaller operations.",
  bool, (void),
  hook_bool_void_false)
 
+DEFHOOK
+(clear_by_pieces,
+ "This target hook should return an rtx that is used to clear memory.\n\
+The default returns @code{const0_rtx}.",
+ rtx, (void *, void *, HOST_WIDE_INT, scalar_int_mode),
+ default_clear_by_pieces)
+
 DEFHOOK
 (compare_by_pieces_branch_ratio,
  "When expanding a block comparison in MODE, gcc can try to reduce the\n\
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 44a1facedcf..ca2f21941e2 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1921,6 +1921,14 @@ default_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT size,
   return by_pieces_ninsns (size, alignment, max_size + 1, op) < ratio;
 }
 
+/* This hook returns an rtx that is used to clear memory.  */
+
+rtx
+default_clear_by_pieces (void *, void *, HOST_WIDE_INT, scalar_int_mode)
+{
+  return const0_rtx;
+}
+
 /* This hook controls code generation for expanding a memcmp operation by
    pieces.  Return 1 for the normal pattern of compare/jump after each pair
    of loads, or a higher number to reduce the number of branches.  */
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index f70a307d26c..fe0e85e9f1f 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -229,6 +229,8 @@ extern bool default_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT,
 						    unsigned int,
 						    enum by_pieces_operation,
 						    bool);
+extern rtx default_clear_by_pieces (void *, void *, HOST_WIDE_INT,
+				    scalar_int_mode);
 extern int default_compare_by_pieces_branch_ratio (machine_mode);
 
 extern void default_print_patchable_function_entry_1 (FILE *,
-- 
2.31.1