On Fri, May 08, 2015 at 10:18:46AM -0400, David Edelsohn wrote:
> > 2015-05-08 Segher Boessenkool <seg...@kernel.crashing.org>
> >
> > * config/rs6000/rs6000.md: Require operand inequality in one
> > of the peepholes.
>
> Okay.
>
> Is there an artificial testcase?
I don't have one. Peepholes require optimisation the be enabled, and
it is hard to get stupid code like this then (a compare of X with X).
But it did trigger a few times in the testsuite with this patch:
diff --git a/gcc/combine.c b/gcc/combine.c
index 46cd6db..8ba14cc 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -3892,8 +3892,8 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
rtx_insn *i0,
&& XVECLEN (newpat, 0) == 2
&& GET_CODE (XVECEXP (newpat, 0, 0)) == SET
&& GET_CODE (XVECEXP (newpat, 0, 1)) == SET
- && (i1 || set_noop_p (XVECEXP (newpat, 0, 0))
- || set_noop_p (XVECEXP (newpat, 0, 1)))
&& GET_CODE (SET_DEST (XVECEXP (newpat, 0, 0))) != ZERO_EXTRACT
&& GET_CODE (SET_DEST (XVECEXP (newpat, 0, 0))) != STRICT_LOW_PART
&& GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != ZERO_EXTRACT
