https://gcc.gnu.org/g:b33e9eb8d404475a45a53afa3e3cc0ff742d75ec
commit r14-11631-gb33e9eb8d404475a45a53afa3e3cc0ff742d75ec
Author: Richard Sandiford <richard.sandif...@arm.com>
Date: Wed Apr 16 13:20:26 2025 +0100
Add force_lowpart_subreg
optabs had a local function called lowpart_subreg_maybe_copy
that is very similar to the lowpart version of force_subreg.
This patch adds a force_lowpart_subreg wrapper around
force_subreg.
The only difference between the old and new functions is that
the old one asserted success while the new one doesn't.
It's common not to assert elsewhere when taking subregs;
normally a null result is enough.
Later patches will make more use of the new function.
gcc/
* explow.h (force_lowpart_subreg): Declare.
* explow.cc (force_lowpart_subreg): New function.
(cherry picked from commit 5f40d1c0cc6ce91ef28d326b8707b3f05e6f239c)
Diff:
---
gcc/explow.cc | 14 ++++++++++++++
gcc/explow.h | 1 +
2 files changed, 15 insertions(+)
diff --git a/gcc/explow.cc b/gcc/explow.cc
index bd93c8780649..2a91cf76ea62 100644
--- a/gcc/explow.cc
+++ b/gcc/explow.cc
@@ -764,6 +764,20 @@ force_subreg (machine_mode outermode, rtx op,
return res;
}
+/* Try to return an rvalue expression for the OUTERMODE lowpart of OP,
+ which has mode INNERMODE. Allow OP to be forced into a new register
+ if necessary.
+
+ Return null on failure. */
+
+rtx
+force_lowpart_subreg (machine_mode outermode, rtx op,
+ machine_mode innermode)
+{
+ auto byte = subreg_lowpart_offset (outermode, innermode);
+ return force_subreg (outermode, op, innermode, byte);
+}
+
/* If X is a memory ref, copy its contents to a new temp reg and return
that reg. Otherwise, return X. */
diff --git a/gcc/explow.h b/gcc/explow.h
index cbd1fcb7eb34..dd654649b068 100644
--- a/gcc/explow.h
+++ b/gcc/explow.h
@@ -43,6 +43,7 @@ extern rtx copy_to_suggested_reg (rtx, rtx, machine_mode);
extern rtx force_reg (machine_mode, rtx);
extern rtx force_subreg (machine_mode, rtx, machine_mode, poly_uint64);
+extern rtx force_lowpart_subreg (machine_mode, rtx, machine_mode);
/* Return given rtx, copied into a new temp reg if it was in memory. */
extern rtx force_not_mem (rtx);
