Bootstrapped and regtested on x86_64-redhat-linux. Ok for master?
The following s390 rtx is errneously considered a no-op:
(set (subreg:DF (reg:TF %f0) 8) (subreg:DF (reg:V1TF %f0) 8))
Here, SET_DEST is a second register in a floating-point register pair,
and SET_SRC is the second half of a vector register, so they refer to
different bits.
Fix by treating subregs of registers in different modes conservatively.
gcc/ChangeLog:
2020-09-11 Ilya Leoshkevich <i...@linux.ibm.com>
* rtlanal.c (set_noop_p): Treat subregs of registers in
different modes conservatively.
---
gcc/rtlanal.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
index 5ae38b7966d..ed3360562d5 100644
--- a/gcc/rtlanal.c
+++ b/gcc/rtlanal.c
@@ -1619,6 +1619,10 @@ set_noop_p (const_rtx set)
return 0;
src = SUBREG_REG (src);
dst = SUBREG_REG (dst);
+ if (GET_MODE (src) != GET_MODE (dst))
+ /* It is hard to tell whether subregs refers to the same bits, so act
+ * conservatively and return 0. */
+ return 0;
}
/* It is a NOOP if destination overlaps with selected src vector
--
2.25.4
