From 1ad584d538d349db13cfa8440222d91d5e9aff3f Mon Sep 17 00:00:00 2001 From: Roger Sayle Date: Mon, 30 May 2022 21:32:58 +0100 Subject: [PATCH] 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 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. --- gcc/config/i386/i386.cc | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index daa60ac..df5c80d 100644 --- a/gcc/config/i386/i386.cc +++ b/gcc/config/i386/i386.cc @@ -20141,6 +20141,18 @@ ix86_modes_tieable_p (machine_mode mode1, machine_mode mode2) return (GET_MODE_SIZE (mode1) == 8 && ix86_hard_regno_mode_ok (FIRST_MMX_REG, mode1)); + /* SCmode and DImode can be tied. */ + if ((mode1 == E_SCmode && mode2 == E_DImode) + || (mode1 == E_DImode && mode2 == E_SCmode)) + return TARGET_64BIT; + + /* [SD]Cmode and V2[SD]Fmode modes can be tied. */ + if ((mode1 == E_SCmode && mode2 == E_V2SFmode) + || (mode1 == E_V2SFmode && mode2 == E_SCmode) + || (mode1 == E_DCmode && mode2 == E_V2DFmode) + || (mode1 == E_V2DFmode && mode2 == E_DCmode)) + return true; + return false; } -- 2.7.4