[PATCH] arm: Fix -mpure-code support/-mslow-flash-data for armv8-m.base [PR94538]

Christophe Lyon christophe.lyon@linaro.org
Mon Aug 24 09:09:38 GMT 2020


On Sat, 22 Aug 2020 at 00:44, Ramana Radhakrishnan
<ramana.gcc@googlemail.com> wrote:
>
> On Wed, Aug 19, 2020 at 10:32 AM Christophe Lyon via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > armv8-m.base (cortex-m23) has the movt instruction, so we need to
> > disable the define_split to generate a constant in this case,
> > otherwise we get incorrect insn constraints as described in PR94538.
> >
> > We also need to fix the pure-code alternative for thumb1_movsi_insn
> > because the assembler complains with instructions like
> > movs r0, #:upper8_15:1234
> > (Internal error in md_apply_fix)
> > We now generate movs r0, 4 instead.
> >
> > 2020-08-19  Christophe Lyon  <christophe.lyon@linaro.org>
> > gcc/ChangeLog:
> >
> >         * config/arm/thumb1.md: Disable set-constant splitter when
> >         TARGET_HAVE_MOVT.
> >         (thumb1_movsi_insn): Fix -mpure-code
> >         alternative.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * gcc.target/arm/pure-code/pr94538-1.c: New test.
> >         * gcc.target/arm/pure-code/pr94538-2.c: New test.
>

Hi Ramana,

>  I take it that this fixes the ICE rather than addressing the code
> generation / performance bits that Wilco was referring to ? Really the
> other code quality / performance issues listed in the PR should really
> be broken down into separate PRs while we take this as a fix for
> fixing the ICE,
>
> Under that assumption OK.
>

Yes, that's correct, this patch just fixes the ICE, as it is cleaner
to handle perf issues in a different patch.

I'll open a new PR to track the perf issue.

Thanks


> Ramana
>
> > ---
> >  gcc/config/arm/thumb1.md                           | 66 ++++++++++++++++++----
> >  gcc/testsuite/gcc.target/arm/pure-code/pr94538-1.c | 13 +++++
> >  gcc/testsuite/gcc.target/arm/pure-code/pr94538-2.c | 12 ++++
> >  3 files changed, 79 insertions(+), 12 deletions(-)
> >  create mode 100644 gcc/testsuite/gcc.target/arm/pure-code/pr94538-1.c
> >  create mode 100644 gcc/testsuite/gcc.target/arm/pure-code/pr94538-2.c
> >
> > diff --git a/gcc/config/arm/thumb1.md b/gcc/config/arm/thumb1.md
> > index 0ff8190..f0129db 100644
> > --- a/gcc/config/arm/thumb1.md
> > +++ b/gcc/config/arm/thumb1.md
> > @@ -70,6 +70,7 @@ (define_split
> >    "TARGET_THUMB1
> >     && arm_disable_literal_pool
> >     && GET_CODE (operands[1]) == CONST_INT
> > +   && !TARGET_HAVE_MOVT
> >     && !satisfies_constraint_I (operands[1])"
> >    [(clobber (const_int 0))]
> >    "
> > @@ -696,18 +697,59 @@ (define_insn "*thumb1_movsi_insn"
> >    "TARGET_THUMB1
> >     && (   register_operand (operands[0], SImode)
> >         || register_operand (operands[1], SImode))"
> > -  "@
> > -   movs        %0, %1
> > -   movs        %0, %1
> > -   movw        %0, %1
> > -   #
> > -   #
> > -   ldmia\\t%1, {%0}
> > -   stmia\\t%0, {%1}
> > -   movs\\t%0, #:upper8_15:%1; lsls\\t%0, #8; adds\\t%0, #:upper0_7:%1; lsls\\t%0, #8; adds\\t%0, #:lower8_15:%1; lsls\\t%0, #8; adds\\t%0, #:lower0_7:%1
> > -   ldr\\t%0, %1
> > -   str\\t%1, %0
> > -   mov\\t%0, %1"
> > +{
> > +  switch (which_alternative)
> > +    {
> > +      default:
> > +      case 0: return "movs\t%0, %1";
> > +      case 1: return "movs\t%0, %1";
> > +      case 2: return "movw\t%0, %1";
> > +      case 3: return "#";
> > +      case 4: return "#";
> > +      case 5: return "ldmia\t%1, {%0}";
> > +      case 6: return "stmia\t%0, {%1}";
> > +      case 7:
> > +      /* pure-code alternative: build the constant byte by byte,
> > +        instead of loading it from a constant pool.  */
> > +       {
> > +         int i;
> > +         HOST_WIDE_INT op1 = INTVAL (operands[1]);
> > +         bool mov_done_p = false;
> > +         rtx ops[2];
> > +         ops[0] = operands[0];
> > +
> > +         /* Emit upper 3 bytes if needed.  */
> > +         for (i = 0; i < 3; i++)
> > +           {
> > +              int byte = (op1 >> (8 * (3 - i))) & 0xff;
> > +
> > +             if (byte)
> > +               {
> > +                 ops[1] = GEN_INT (byte);
> > +                 if (mov_done_p)
> > +                   output_asm_insn ("adds\t%0, %1", ops);
> > +                 else
> > +                   output_asm_insn ("movs\t%0, %1", ops);
> > +                 mov_done_p = true;
> > +               }
> > +
> > +             if (mov_done_p)
> > +               output_asm_insn ("lsls\t%0, #8", ops);
> > +           }
> > +
> > +         /* Emit lower byte if needed.  */
> > +         ops[1] = GEN_INT (op1 & 0xff);
> > +         if (!mov_done_p)
> > +           output_asm_insn ("movs\t%0, %1", ops);
> > +         else if (op1 & 0xff)
> > +           output_asm_insn ("adds\t%0, %1", ops);
> > +         return "";
> > +       }
> > +      case 8: return "ldr\t%0, %1";
> > +      case 9: return "str\t%1, %0";
> > +      case 10: return "mov\t%0, %1";
> > +    }
> > +}
> >    [(set_attr "length" "2,2,4,4,4,2,2,14,2,2,2")
> >     (set_attr "type" "mov_reg,mov_imm,mov_imm,multiple,multiple,load_4,store_4,alu_sreg,load_4,store_4,mov_reg")
> >     (set_attr "pool_range" "*,*,*,*,*,*,*, *,1018,*,*")
> > diff --git a/gcc/testsuite/gcc.target/arm/pure-code/pr94538-1.c b/gcc/testsuite/gcc.target/arm/pure-code/pr94538-1.c
> > new file mode 100644
> > index 0000000..31061d5
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pure-code/pr94538-1.c
> > @@ -0,0 +1,13 @@
> > +/* { dg-do compile } */
> > +/* { dg-skip-if "skip override" { *-*-* } { "-mfloat-abi=hard" } { "" } } */
> > +/* { dg-options "-mpure-code -mcpu=cortex-m23 -march=armv8-m.base -mthumb -mfloat-abi=soft" } */
> > +
> > +typedef int __attribute__ ((__vector_size__ (16))) V;
> > +
> > +V v;
> > +
> > +void
> > +foo (void)
> > +{
> > +  v += (V){4095};
> > +}
> > diff --git a/gcc/testsuite/gcc.target/arm/pure-code/pr94538-2.c b/gcc/testsuite/gcc.target/arm/pure-code/pr94538-2.c
> > new file mode 100644
> > index 0000000..c1789da
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pure-code/pr94538-2.c
> > @@ -0,0 +1,12 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-mpure-code" } */
> > +
> > +typedef int __attribute__ ((__vector_size__ (16))) V;
> > +
> > +V v;
> > +
> > +void
> > +foo (void)
> > +{
> > +  v += (V){4095};
> > +}
> > --
> > 2.7.4
> >


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