https://gcc.gnu.org/bugzilla/show_bug.cgi?id=7061
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:1ad584d538d349db13cfa8440222d91d5e9aff3f commit r13-859-g1ad584d538d349db13cfa8440222d91d5e9aff3f Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Mon May 30 21:32:58 2022 +0100 Allow SCmode and DImode to be tieable with TARGET_64BIT on x86_64. This patch is a form of insurance policy in case my patch for PR 7061 runs into problems on non-x86 targets; the middle-end can add an extra check that the backend is happy placing SCmode and DImode values in the same register, before creating a SUBREG. Unfortunately, ix86_modes_tieable_p currently claims this is not allowed(?), even though the default target hook for modes_tieable_p is to always return true [i.e. false can be used to specifically prohibit bad combinations], and the x86_64 ABI passes SCmode values in DImode registers!. This makes the backend's modes_tiable_p hook a little more forgiving, and additionally enables interconversion between SCmode and V2SFmode, and between DCmode and VD2Fmode, which opens interesting opporutunities in the future. 2022-05-30 Roger Sayle <ro...@nextmovesoftware.com> gcc/ChangeLog * config/i386/i386.cc (ix86_modes_tieable_p): Allow SCmode to be tieable with DImode on TARGET_64BIT, and SCmode tieable with V2SFmode, and DCmode with V2DFmode.
