When I converted xstormy16'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.
This patch has been tested by building a cross compiler to xstormy16-elf
from x86_64-pc-linux-gnu. Committed as obvious (in hindsight).
2023-04-30 Roger Sayle <ro...@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.
Sorry for any inconvenience.
Roger
--
diff --git a/gcc/config/stormy16/stormy16.md b/gcc/config/stormy16/stormy16.md
index be1ee04..91e4bb1 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 dd3dd1e..101c6da 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" } } */
