Hi!
On Sat, Oct 08, 2016 at 07:53:42PM +0200, Eric Botcazou wrote:
> this fixes reload failures in 64-bit mode with -mcmodel=medium for targets
> that define ASM_OUTPUT_SPECIAL_POOL_ENTRY_P to 0; that's the case for the
> VxWorks port we'll submit because of the compatibility with the system
> linker,
> which rejects .got sections in object files.
>
> When reload ends up calling rs6000_emit_move on a register on the LHS and
> (const (symbol_ref) (const_int)) on the RHS, the function invokes:
>
> operands[1] = force_const_mem (mode, operands[1]);
>
> creating (mem (symbol_ref)), which then needs to be legitimized on TARGET_TOC
> targets. That's done by the immediately following block:
>
> if (TARGET_TOC
> && GET_CODE (XEXP (operands[1], 0)) == SYMBOL_REF
> && constant_pool_expr_p (XEXP (operands[1], 0))
> && ASM_OUTPUT_SPECIAL_POOL_ENTRY_P (
> get_pool_constant (XEXP (operands[1], 0)),
> get_pool_mode (XEXP (operands[1], 0))))
> {
> rtx tocref = create_TOC_reference (XEXP (operands[1], 0),
> operands[0]);
> operands[1] = gen_const_mem (mode, tocref);
> set_mem_alias_set (operands[1], get_TOC_alias_set ());
> }
>
> on most targets, but is disabled if ASM_OUTPUT_SPECIAL_POOL_ENTRY_P is 0.
Why does this not fail on darwin? It can reach this code afaics, and
it has ASM_OUTPUT_SPECIAL_POOL_ENTRY_P always 0.
> Now you don't need to have a special pool to call create_TOC_reference, you
> can call it for regular TOC references as well, as done a few lines above:
>
> /* If this is a SYMBOL_REF that refers to a constant pool entry,
> and we have put it in the TOC, we just need to make a TOC-relative
> reference to it. */
> if (TARGET_TOC
> && GET_CODE (operands[1]) == SYMBOL_REF
> && use_toc_relative_ref (operands[1], mode))
> operands[1] = create_TOC_reference (operands[1], operands[0]);
>
> So the attached patch does it there too.
>
> Tested on PowerPC64/Linux (LRA) and VxWorks (reload), OK for the mainline?
Not sure yet, will get back to you. One comment in the meantime...
> --- config/rs6000/rs6000.c (revision 240888)
> +++ config/rs6000/rs6000.c (working copy)
> @@ -10590,10 +10590,7 @@ rs6000_emit_move (rtx dest, rtx source,
>
> if (TARGET_TOC
> && GET_CODE (XEXP (operands[1], 0)) == SYMBOL_REF
> - && constant_pool_expr_p (XEXP (operands[1], 0))
> - && ASM_OUTPUT_SPECIAL_POOL_ENTRY_P (
> - get_pool_constant (XEXP (operands[1], 0)),
> - get_pool_mode (XEXP (operands[1], 0))))
> + && use_toc_relative_ref (XEXP (operands[1], 0), Pmode))
Use "mode" instead of "Pmode" here?
Segher
