The following adds a target hook to specify whether regs of MODE can be
used to transfer bits. The hook is supposed to be used for value-numbering
to decide whether a value loaded in such mode can be punned to another
mode instead of re-loading the value in the other mode and for SRA to
decide whether MODE is suitable as container holding a value to be
used in different modes.
Bootstrapped and tested on x86_64-unknown-linux-gnu, OK this way?
Thanks,
Richard.
* target.def (mode_can_transfer_bits): New target hook.
* target.h (mode_can_transfer_bits): New function wrapping the
hook and providing default behavior.
* doc/tm.texi.in: Update.
* doc/tm.texi: Re-generate.
---
gcc/doc/tm.texi | 6 ++++++
gcc/doc/tm.texi.in | 2 ++
gcc/target.def | 8 ++++++++
gcc/target.h | 16 ++++++++++++++++
4 files changed, 32 insertions(+)
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index c7535d07f4d..fa53c23f1de 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -4545,6 +4545,12 @@ is either a declaration of type int or accessed by
dereferencing
a pointer to int.
@end deftypefn
+@deftypefn {Target Hook} bool TARGET_MODE_CAN_TRANSFER_BITS (machine_mode
@var{mode})
+Define this to return false if the mode @var{mode} cannot be used
+for memory copying. The default is to assume modes with the same
+precision as size are fine to be used.
+@end deftypefn
+
@deftypefn {Target Hook} machine_mode TARGET_TRANSLATE_MODE_ATTRIBUTE
(machine_mode @var{mode})
Define this hook if during mode attribute processing, the port should
translate machine_mode @var{mode} to another mode. For example, rs6000's
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 64cea3b1eda..8af3f414505 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -3455,6 +3455,8 @@ stack.
@hook TARGET_REF_MAY_ALIAS_ERRNO
+@hook TARGET_MODE_CAN_TRANSFER_BITS
+
@hook TARGET_TRANSLATE_MODE_ATTRIBUTE
@hook TARGET_SCALAR_MODE_SUPPORTED_P
diff --git a/gcc/target.def b/gcc/target.def
index 3de1aad4c84..4356ef2f974 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -3363,6 +3363,14 @@ a pointer to int.",
bool, (ao_ref *ref),
default_ref_may_alias_errno)
+DEFHOOK
+(mode_can_transfer_bits,
+ "Define this to return false if the mode @var{mode} cannot be used\n\
+for memory copying. The default is to assume modes with the same\n\
+precision as size are fine to be used.",
+ bool, (machine_mode mode),
+ NULL)
+
/* Support for named address spaces. */
#undef HOOK_PREFIX
#define HOOK_PREFIX "TARGET_ADDR_SPACE_"
diff --git a/gcc/target.h b/gcc/target.h
index c1f99b97b86..837651d273a 100644
--- a/gcc/target.h
+++ b/gcc/target.h
@@ -312,6 +312,22 @@ estimated_poly_value (poly_int64 x,
return targetm.estimated_poly_value (x, kind);
}
+/* Return true when MODE can be used to copy GET_MODE_BITSIZE bits
+ unchanged. */
+
+inline bool
+mode_can_transfer_bits (machine_mode mode)
+{
+ if (mode == BLKmode)
+ return true;
+ if (maybe_ne (GET_MODE_BITSIZE (mode),
+ GET_MODE_UNIT_PRECISION (mode) * GET_MODE_NUNITS (mode)))
+ return false;
+ if (targetm.mode_can_transfer_bits)
+ return targetm.mode_can_transfer_bits (mode);
+ return true;
+}
+
#ifdef GCC_TM_H
#ifndef CUMULATIVE_ARGS_MAGIC
--
2.43.0
