Some target like RISC-V allow to group vector register as a whole,
and only operate part of it in fact, but the 'init-regs' pass will add
initialization
for uninitialized registers. Add this hook to reject this action for reducing
instruction.
gcc/
* init-regs.c (initialize_uninitialized_regs): Call
register_reject_init_p.
* target.def (register_reject_init_p): New hook.
* doc/tm.texi.in: Add TARGET_REGISTER_REJECT_INIT_P.
* doc/tm.texi: Regenerated.
---
gcc/doc/tm.texi | 6 ++++++
gcc/doc/tm.texi.in | 2 ++
gcc/init-regs.c | 5 +++++
gcc/target.def | 8 ++++++++
4 files changed, 21 insertions(+)
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index a30fdcbbf3d6..83fd5496ca3f 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -12588,3 +12588,9 @@ Return an RTX representing @var{tagged_pointer} with
its tag set to zero.
Store the result in @var{target} if convenient.
The default clears the top byte of the original pointer.
@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_REGISTER_REJECT_INIT_P (rtx @var{reg})
+This target hook should return @code{true} if reject initialization for a
uninitialized @var{reg}.
+
+The default value of this hook is @code{NULL}.
+@end deftypefn
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 611fc500ac86..13174ce66d59 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -8180,3 +8180,5 @@ maintainer is familiar with.
@hook TARGET_MEMTAG_EXTRACT_TAG
@hook TARGET_MEMTAG_UNTAGGED_POINTER
+
+@hook TARGET_REGISTER_REJECT_INIT_P
diff --git a/gcc/init-regs.c b/gcc/init-regs.c
index 72e898f3e334..51c0d669d30b 100644
--- a/gcc/init-regs.c
+++ b/gcc/init-regs.c
@@ -21,6 +21,7 @@ along with GCC; see the file COPYING3. If not see
#include "system.h"
#include "coretypes.h"
#include "backend.h"
+#include "target.h"
#include "rtl.h"
#include "tree.h"
#include "df.h"
@@ -101,6 +102,10 @@ initialize_uninitialized_regs (void)
rtx_insn *move_insn;
rtx reg = DF_REF_REAL_REG (use);
+ if (targetm.register_reject_init_p
+ && targetm.register_reject_init_p (reg))
+ continue;
+
bitmap_set_bit (already_genned, regno);
start_sequence ();
diff --git a/gcc/target.def b/gcc/target.def
index 7676d5e626e3..c2b54421618d 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -4545,6 +4545,14 @@ by a subtarget.",
unsigned HOST_WIDE_INT, (void),
NULL)
+/* Return true if reject initialization for a uninitialized register. */
+DEFHOOK
+(register_reject_init_p,
+ "This target hook should return @code{true} if reject initialization for a
uninitialized @var{reg}.\n\
+\n\
+The default value of this hook is @code{NULL}.",
+ bool, (rtx reg), NULL)
+
/* Functions relating to calls - argument passing, returns, etc. */
/* Members of struct call have no special macro prefix. */
HOOK_VECTOR (TARGET_CALLS, calls)
--
2.24.3 (Apple Git-128)
