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* [gcc r13-859] Allow SCmode and DImode to be tieable with TARGET_64BIT on x86_64.
@ 2022-05-30 20:40 Roger Sayle
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From: Roger Sayle @ 2022-05-30 20:40 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:1ad584d538d349db13cfa8440222d91d5e9aff3f
commit r13-859-g1ad584d538d349db13cfa8440222d91d5e9aff3f
Author: Roger Sayle <roger@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 <roger@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.
Diff:
---
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 daa60acdc05..df5c80dc0e7 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;
}
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