Richard Henderson <r...@redhat.com> writes:
> @@ -10808,6 +10808,13 @@ mips_cannot_change_mode_class (enum machine_mode
> from ATTRIBUTE_UNUSED,
> format.
>
> We therefore disallow all mode changes involving FPRs. */
> +
> + /* Except for Loongson and its integral vectors. We need to be able
> + to change between those modes easily. */
> + if (GET_MODE_SIZE (from) == 8 && GET_MODE_SIZE (to) == 8
> + && INTEGRAL_MODE_P (from) && INTEGRAL_MODE_P (to))
> + return false;
> +
> return reg_classes_intersect_p (FP_REGS, rclass);
> }
I'm lumbering you with a private hobby horse, but would you mind using
the attached instead? I just want to avoid the "Here's a long explanation
of why we must do X. Oh, but don't do X in this one case." style of comment.
Richard
Index: gcc/config/mips/mips.c
===================================================================
--- gcc/config/mips/mips.c 2011-12-22 18:29:39.000000000 +0000
+++ gcc/config/mips/mips.c 2011-12-22 18:31:24.000000000 +0000
@@ -10782,12 +10782,18 @@ mips_class_max_nregs (enum reg_class rcl
/* Implement CANNOT_CHANGE_MODE_CLASS. */
bool
-mips_cannot_change_mode_class (enum machine_mode from ATTRIBUTE_UNUSED,
- enum machine_mode to ATTRIBUTE_UNUSED,
+mips_cannot_change_mode_class (enum machine_mode from,
+ enum machine_mode to,
enum reg_class rclass)
{
- /* There are several problems with changing the modes of values in
- floating-point registers:
+ /* Allow conversions between different Loongson integer vectors,
+ and between those vectors and DImode. */
+ if (GET_MODE_SIZE (from) == 8 && GET_MODE_SIZE (to) == 8
+ && INTEGRAL_MODE_P (from) && INTEGRAL_MODE_P (to))
+ return false;
+
+ /* Otherwise, there are several problems with changing the modes of
+ values in floating-point registers:
- When a multi-word value is stored in paired floating-point
registers, the first register always holds the low word. We
