Re: [PATCH] LoongArch: Fix infinite secondary reloading of FCCmode [PR113148]

[chenglulu <chenglulu@loongson.cn>]

在 2023/12/27 上午6:37, Xi Ruoyao 写道:
> The GCC internal doc says:
>
>       X might be a pseudo-register or a 'subreg' of a pseudo-register,
>       which could either be in a hard register or in memory.  Use
>       'true_regnum' to find out; it will return -1 if the pseudo is in
>       memory and the hard register number if it is in a register.
>
> So "MEM_P (x)" is not enough for checking if we are reloading from/to
> the memory.  This bug has caused reload pass to stall and finally ICE
> complaining with "maximum number of generated reload insns per insn
> achieved", since r14-6814.
>
> Check if "true_regnum (x)" is -1 besides "MEM_P (x)" to fix the issue.
>
> gcc/ChangeLog:
>
> 	PR target/113148
> 	* config/loongarch/loongarch.cc (loongarch_secondary_reload):
> 	Check if regno == -1 besides MEM_P (x) for reloading FCCmode
> 	from/to FPR to/from memory.
>
> gcc/testsuite/ChangeLog:
>
> 	PR target/113148
> 	* gcc.target/loongarch/pr113148.c: New test.
> ---
>
> Bootstrapped & regtested on loongarch64-linux-gnu.  Ok for trunk?

LGTM!

Thanks!

>
>   gcc/config/loongarch/loongarch.cc             |  3 +-
>   gcc/testsuite/gcc.target/loongarch/pr113148.c | 44 +++++++++++++++++++
>   2 files changed, 46 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/gcc.target/loongarch/pr113148.c
>
> diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
> index 5ffd06ce9be..c0a0af3dda5 100644
> --- a/gcc/config/loongarch/loongarch.cc
> +++ b/gcc/config/loongarch/loongarch.cc
> @@ -6951,7 +6951,8 @@ loongarch_secondary_reload (bool in_p ATTRIBUTE_UNUSED, rtx x,
>   	  return NO_REGS;
>   	}
>   
> -      if (reg_class_subset_p (rclass, FP_REGS) && MEM_P (x))
> +      if (reg_class_subset_p (rclass, FP_REGS)
> +	  && (regno == -1 || MEM_P (x)))
>   	return GR_REGS;
>   
>         return NO_REGS;
> diff --git a/gcc/testsuite/gcc.target/loongarch/pr113148.c b/gcc/testsuite/gcc.target/loongarch/pr113148.c
> new file mode 100644
> index 00000000000..cf48e552053
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/loongarch/pr113148.c
> @@ -0,0 +1,44 @@
> +/* PR 113148: ICE caused by infinite reloading */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -march=la464 -mfpu=64 -mabi=lp64d" } */
> +
> +struct bound
> +{
> +  double max;
> +} drawQuadrant_bound;
> +double w4, innerXfromXY_y, computeBound_right_0;
> +struct arc_def
> +{
> +  double w, h;
> +  double a0, a1;
> +};
> +static void drawQuadrant (struct arc_def *);
> +static void
> +computeBound (struct arc_def *def, struct bound *bound)
> +{
> +  double ellipsex_1, ellipsex_0;
> +  bound->max = def->a1 ?: __builtin_sin (w4) * def->h;
> +  if (def->a0 == 5 && def->w == def->h)
> +    ;
> +  else
> +    ellipsex_0 = def->a0 == 0.0 ?: __builtin_cos (w4);
> +  if (def->a1 == 5 && def->w == def->h)
> +    ellipsex_1 = bound->max;
> +  __builtin_sqrt (ellipsex_1 * innerXfromXY_y * innerXfromXY_y * w4);
> +  computeBound_right_0 = ellipsex_0;
> +}
> +void
> +drawArc ()
> +{
> +  struct arc_def foo;
> +  for (;;)
> +    drawQuadrant (&foo);
> +}
> +void
> +drawQuadrant (struct arc_def *def)
> +{
> +  int y, miny;
> +  computeBound (def, &drawQuadrant_bound);
> +  while (y >= miny)
> +    ;
> +}