From: "Roger Sayle" <roger@nextmovesoftware.com>
To: "'GCC Patches'" <gcc-patches@gcc.gnu.org>
Subject: [xstormy16 PATCH] Efficient HImode rotate left by a single bit.
Date: Sat, 29 Apr 2023 17:25:48 +0100 [thread overview]
Message-ID: <004a01d97ab7$42722140$c75663c0$@nextmovesoftware.com> (raw)
[-- Attachment #1: Type: text/plain, Size: 1270 bytes --]
This patch contains some minor tweak to xstormy16's machine description
most significantly providing a pattern for HImode rotate left by a single
bit that requires only two instructions.
unsigned short foo(unsigned short x)
{
return (x << 1) | (x >> 15);
}
currently with -O2 generates:
foo: mov r7,r2
shr r7,#15
shl r2,#1
or r2,r7
ret
with this patch, GCC now generates:
foo: shl r2,#1 | adc r2,#0
ret
Additionally neghi2 is converted to a define_insn (so that the RTL
optimizers see the negation semantics), and HImode rotations by
8-bits can now be recognized and implemented using swpb.
This patch has been tested by building a cross-compiler to xstormy16-elf
from x86_64-pc-linux-gnu and confirming the new test cases pass.
Ok for mainline?
2023-04-29 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
* config/stormy16/stormy16.md (neghi2): Convert from a define_expand
to a define_insn.
(*rotatehi_1): New define_insn for efficient 2 insn sequence.
(*rotatehi_8, *rotaterthi_8): New define_insn to emit a swpb.
gcc/testsuite/ChangeLog
* gcc.target/xstormy16/neghi2.c: New test case.
* gcc.target/rotatehi-1.c: Likewise.
Thanks in advance,
Roger
--
[-- Attachment #2: patchxs2.txt --]
[-- Type: text/plain, Size: 2283 bytes --]
diff --git a/gcc/config/stormy16/stormy16.md b/gcc/config/stormy16/stormy16.md
index b2e86ee..be1ee04 100644
--- a/gcc/config/stormy16/stormy16.md
+++ b/gcc/config/stormy16/stormy16.md
@@ -514,13 +518,13 @@
;; Negation
-(define_expand "neghi2"
- [(set (match_operand:HI 0 "register_operand" "")
- (not:HI (match_operand:HI 1 "register_operand" "")))
- (parallel [(set (match_dup 0) (plus:HI (match_dup 0) (const_int 1)))
+(define_insn "neghi2"
+ [(parallel [(set (match_operand:HI 0 "register_operand" "=r")
+ (neg:HI (match_operand:HI 1 "register_operand" "0")))
(clobber (reg:BI CARRY_REG))])]
""
- "")
+ "not %0 | add %0,#1"
+ [(set_attr "length" "4")])
\f
;; ::::::::::::::::::::
;; ::
@@ -554,6 +558,24 @@
(clobber (reg:BI CARRY_REG))]
""
"shr %0,%2")
+
+;; HImode rotate left by 1 bit
+(define_insn "*rotatehi_1"
+ [(set (match_operand:HI 0 "register_operand" "=r")
+ (rotate:HI (match_operand:HI 1 "register_operand" "0")
+ (const_int 1)))
+ (clobber (reg:BI CARRY_REG))]
+ ""
+ "shl %0,#1 | adc %0,#0"
+ [(set_attr "length" "4")])
+
+;; HImode rotate left by 8 bits
+(define_insn "*<code>hi_8"
+ [(set (match_operand:HI 0 "register_operand" "=r")
+ (any_rotate:HI (match_operand:HI 1 "register_operand" "0")
+ (const_int 8)))]
+ ""
+ "swpb %0")
\f
;; ::::::::::::::::::::
;; ::
diff --git a/gcc/testsuite/gcc.target/xstormy16/neghi2.c b/gcc/testsuite/gcc.target/xstormy16/neghi2.c
new file mode 100644
index 0000000..dd3dd1e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xstormy16/neghi2.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+short neg(short x)
+{
+ return -x;
+}
+/* { dg-final { scan-assembler "not r2 | add r2,#1" } } */
diff --git a/gcc/testsuite/gcc.target/xstormy16/rotatehi-1.c b/gcc/testsuite/gcc.target/xstormy16/rotatehi-1.c
new file mode 100644
index 0000000..586e7dc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xstormy16/rotatehi-1.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned short foo(unsigned short x)
+{
+ return (x << 1) | (x >> 15);
+}
+
+/* { dg-final { scan-assembler "shl r2,#1" } } */
+/* { dg-final { scan-assembler "adc r2,#0" } } */
next reply other threads:[~2023-04-29 16:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-29 16:25 Roger Sayle [this message]
2023-04-29 16:42 ` Jeff Law
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='004a01d97ab7$42722140$c75663c0$@nextmovesoftware.com' \
--to=roger@nextmovesoftware.com \
--cc=gcc-patches@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).