On Mon, 27 Jan 2025, Jakub Jelinek wrote: > On Mon, Jan 27, 2025 at 11:09:38AM +0100, Richard Biener wrote: > > PR rtl-optimization/118662 > > * combine.cc (try_combine): When re-materializing a load > > from an extended reg by a lowpart subreg make sure we're > > dealing with single-component modes. > > > > * gcc.dg/torture/pr118662.c: New testcase. > > --- > > gcc/combine.cc | 5 +++++ > > gcc/testsuite/gcc.dg/torture/pr118662.c | 18 ++++++++++++++++++ > > 2 files changed, 23 insertions(+) > > create mode 100644 gcc/testsuite/gcc.dg/torture/pr118662.c > > > > diff --git a/gcc/combine.cc b/gcc/combine.cc > > index a2d4387cebe..4849603ba5e 100644 > > --- a/gcc/combine.cc > > +++ b/gcc/combine.cc > > @@ -3904,6 +3904,9 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn > > *i1, rtx_insn *i0, > > copy. This saves at least one insn, more if register allocation can > > eliminate the copy. > > > > + We cannot do this if the involved modes have more than one elements, > > + like for vector or complex modes. > > + > > We cannot do this if the destination of the first assignment is a > > condition code register. We eliminate this case by making sure > > the SET_DEST and SET_SRC have the same mode. > > @@ -3919,6 +3922,8 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn > > *i1, rtx_insn *i0, > > && GET_CODE (SET_SRC (XVECEXP (newpat, 0, 0))) == SIGN_EXTEND > > && (GET_MODE (SET_DEST (XVECEXP (newpat, 0, 0))) > > == GET_MODE (SET_SRC (XVECEXP (newpat, 0, 0)))) > > + && known_eq (GET_MODE_NUNITS > > + (GET_MODE (SET_DEST (XVECEXP (newpat, 0, 0)))), 1) > > If you want to rule this out for vector/complex modes, then the above > doesn't do that, all the V1??mode will still be optimized, and I think > that is undesirable.
If you think so (I think it should work fine for V1??mode). > So, either && !VECTOR_MODE_P (GET_MODE (...)) > && !COMPLEX_MODE_P (GET_MODE (...)) > or perhaps as less expensive but less readable check > && GET_MODE_INNER (GET_MODE (...)) == GET_MODE (...) Had the latter before figuring the GET_MODE_NUNITS variant. I do prefer a "positive" check, rtl.texi says sign_extend applies to all fixed-point modes but ALL_SCALAR_FIXED_POINT_MODE_P doesn't include regular MODE_INT. I guess I'll go with !VECTOR_MODE_P && !COMPLEX_MODE_P, while SCALAR_INT_MODE_P looks safe it might cause regressions. Thanks, Richard. > with a comment. > > Jakub > > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
