[ARM] Fix -mpure-code for v6m

[Christophe Lyon]

On Fri, 7 Feb 2020 at 14:49, Richard Earnshaw (lists)
<Richard.Earnshaw@arm.com> wrote:
>
> On 07/02/2020 13:19, Christophe Lyon wrote:
> > When running the testsuite with -fdisable-rtl-fwprop2 and -mpure-code
> > for cortex-m0, I noticed that some testcases were failing because we
> > still generate "ldr rX, .LCY", which is what we want to avoid with
> > -mpure-code. This is latent since a recent improvement in fwprop
> > (PR88833).
> >
> > In this patch I change the thumb1_movsi_insn pattern so that it emits
> > the desired instruction sequence when arm_disable_literal_pool is set.
> >
> > I tried to add a define_split instead, but couldn't make it work: the
> > compiler then complains it cannot split the instruction, while my new
> > define_split accepts the same operand types as thumb1_movsi_insn:
> >
> > c-c++-common/torture/complex-sign-mixed-add.c:41:1: error: could not split insn
> > (insn 2989 425 4844 (set (reg/f:SI 3 r3 [1342])
> >          (symbol_ref/u:SI ("*.LC6") [flags 0x2])) 836 {*thumb1_movsi_insn}
> >       (expr_list:REG_EQUIV (symbol_ref/u:SI ("*.LC6") [flags 0x2])
> >          (nil)))
> > during RTL pass: final
> >
> > (define_split
> >    [(set (match_operand:SI 0 "register_operand" "")
> >          (match_operand:SI 1 "general_operand" ""))]
> >    "TARGET_THUMB1
> >     && arm_disable_literal_pool
> >     && GET_CODE (operands[1]) == SYMBOL_REF"
> >    [(clobber (const_int 0))]
> >    "
> >      gen_thumb1_movsi_symbol_ref(operands[0], operands[1]);
> >      DONE;
> >    "
> > )
> > and I put this in thumb1_movsi_insn:
> > if (GET_CODE (operands[1]) == SYMBOL_REF && arm_disable_literal_pool)
> >    {
> >      return \"#\";
> >    }
> >    return \"ldr\\t%0, %1\";
> >
> > 2020-02-07  Christophe Lyon  <christophe.lyon@linaro.org>
> >
> >          * config/arm/thumb1.md (thumb1_movsi_insn): Fix ldr alternative to
> >          work with -mpure-code.
> >
>
> +    case 0:
> +    case 1:
> +      return \"movs    %0, %1\";
> +    case 2:
> +      return \"movw    %0, %1\";
>
> This is OK, but please replace the hard tab in the strings for MOVS/MOVW
> with \\t.
>

OK that was merely a cut & paste from the existing code.

I'm concerned that the length attribute is becoming wrong with my
patch, isn't this a problem?

Thanks,

Christophe

> R.