From: Roger Sayle <roger@nextmovesoftware.com>
Date: Sun, 30 Apr 2023 22:47:13 +0000 (+0100)
Subject: [Committed] Update xstormy16's neghi2 pattern to not clobber the carry flag.
X-Git-Tag: basepoints/gcc-15~9774
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b159026b739f46e6d552bb23e8f51f03e291f51e;p=thirdparty%2Fgcc.git

[Committed] Update xstormy16's neghi2 pattern to not clobber the carry flag.

When I converted xstormy's neghi2 pattern from a define_expand to a
define_insn, I forgot that define_expand implicitly produces a
sequence of instructions, but a define_insn is an implicit parallel,
thereby messing up the clobber (reg:BI CARRY_REG), which can then cause
an ICE in the auto-generated added_clobbers_hard_reg_p.  Whilst stripping
the superfluous PARALLEL resolves this issue, an even better fix is to
use xstormy16's INC instruction, that (like NOT) doesn't affect the carry
flag, resulting in a neghi2 implementation that can more easily be CSE'd
and scheduled.

Many thanks (again) to Jeff Law for testing/reporting this issue.

2024-04-30  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/stormy16/stormy16.md (neghi2): Rewrite pattern using
	inc to avoid clobbering the carry flag.

gcc/testsuite/ChangeLog
	* gcc.target/xstormy16/neghi2.c: Update expected implementation.
---

diff --git a/gcc/config/stormy16/stormy16.md b/gcc/config/stormy16/stormy16.md
index be1ee04e5b58..91e4bb1cff7f 100644
--- a/gcc/config/stormy16/stormy16.md
+++ b/gcc/config/stormy16/stormy16.md
@@ -519,11 +519,10 @@
 ;; Negation
 
 (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))])]
+  [(set (match_operand:HI 0 "register_operand" "=r")
+	(neg:HI (match_operand:HI 1 "register_operand" "0")))]
   ""
-  "not %0 | add %0,#1"
+  "not %0 | inc %0"
   [(set_attr "length" "4")])
 
 ;; ::::::::::::::::::::
diff --git a/gcc/testsuite/gcc.target/xstormy16/neghi2.c b/gcc/testsuite/gcc.target/xstormy16/neghi2.c
index dd3dd1e60fb9..101c6da279f8 100644
--- a/gcc/testsuite/gcc.target/xstormy16/neghi2.c
+++ b/gcc/testsuite/gcc.target/xstormy16/neghi2.c
@@ -5,4 +5,4 @@ short neg(short x)
 {
   return -x;
 }
-/* { dg-final { scan-assembler "not r2 | add r2,#1" } } */
+/* { dg-final { scan-assembler "not r2 | inc r2" } } */