RE: [PATCH][ARM] Fix -fcall-saved-rX for X > 7 with -Os -mthumb

["Thomas Preud'homme" <thomas dot preudhomme at arm dot com>]

Ping?

> -----Original Message-----
> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> owner@gcc.gnu.org] On Behalf Of Thomas Preud'homme
> Sent: Wednesday, August 20, 2014 9:28 AM
> To: gcc-patches@gcc.gnu.org
> Subject: [PATCH][ARM] Fix -fcall-saved-rX for X > 7
> 
> This patch makes -fcall-saved-rX for X > 7 on Thumb target when
> optimizing for size. It works by adding a new field
> x_user_set_call_save_regs in struct target_hard_regs to track whether
> an entry in fields x_fixed_regs, x_call_used_regs and
> x_call_really_used_regs was user set or is in its default value. Then it can
> decide whether to set a given high register as caller saved or not when
> optimizing for size based on this information.
> 
> ChangeLog are as follows:
> 
> *** gcc/ChangeLog ***
> 
> 2014-08-15  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
>         * config/arm/arm.c (arm_conditional_register_usage): Only set high
>         registers as caller saved when optimizing for size *and* the user did
>         not asked otherwise through -fcall-saved-* switch.
>         * hard-reg-set.h (x_user_set_call_save_regs): New.
>         (user_set_call_save_regs): Define.
>         * reginfo.c (init_reg_sets): Initialize user_set_call_save_regs.
>         (fix_register): Indicate in user_set_call_save_regs that the value set
>         in call_save_regs and fixed_regs is user set.
> 
> 
> *** gcc/testsuite/ChangeLog ***
> 
> 2014-08-15  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
>         * gcc.target/arm/fcall-save-rhigh.c: New.
> 
> 
> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> index 2f8d327..8324fa3 100644
> --- a/gcc/config/arm/arm.c
> +++ b/gcc/config/arm/arm.c
> @@ -30084,7 +30084,8 @@ arm_conditional_register_usage (void)
>          stacking them.  */
>        for (regno = FIRST_HI_REGNUM;
>  	   regno <= LAST_HI_REGNUM; ++regno)
> -	fixed_regs[regno] = call_used_regs[regno] = 1;
> +	if (!user_set_call_save_regs[regno])
> +	  fixed_regs[regno] = call_used_regs[regno] = 1;
>      }
> 
>    /* The link register can be clobbered by any branch insn,
> diff --git a/gcc/hard-reg-set.h b/gcc/hard-reg-set.h
> index b8ab3df..b523637 100644
> --- a/gcc/hard-reg-set.h
> +++ b/gcc/hard-reg-set.h
> @@ -614,6 +614,11 @@ struct target_hard_regs {
> 
>    char x_call_really_used_regs[FIRST_PSEUDO_REGISTER];
> 
> +  /* Indexed by hard register number, contains 1 for registers
> +     whose saving at function call was decided by the user
> +     with -fcall-saved-*, -fcall-used-* or -ffixed-*.  */
> +  char x_user_set_call_save_regs[FIRST_PSEUDO_REGISTER];
> +
>    /* The same info as a HARD_REG_SET.  */
>    HARD_REG_SET x_call_used_reg_set;
> 
> @@ -685,6 +690,8 @@ extern struct target_hard_regs
> *this_target_hard_regs;
>    (this_target_hard_regs->x_call_used_regs)
>  #define call_really_used_regs \
>    (this_target_hard_regs->x_call_really_used_regs)
> +#define user_set_call_save_regs \
> +  (this_target_hard_regs->x_user_set_call_save_regs)
>  #define call_used_reg_set \
>    (this_target_hard_regs->x_call_used_reg_set)
>  #define call_fixed_reg_set \
> diff --git a/gcc/reginfo.c b/gcc/reginfo.c
> index 7668be0..0b35f7f 100644
> --- a/gcc/reginfo.c
> +++ b/gcc/reginfo.c
> @@ -183,6 +183,7 @@ init_reg_sets (void)
>    memcpy (call_really_used_regs, initial_call_really_used_regs,
>  	  sizeof call_really_used_regs);
>  #endif
> +  memset (user_set_call_save_regs, 0, sizeof user_set_call_save_regs);
>  #ifdef REG_ALLOC_ORDER
>    memcpy (reg_alloc_order, initial_reg_alloc_order, sizeof
> reg_alloc_order);
>  #endif
> @@ -742,6 +743,7 @@ fix_register (const char *name, int fixed, int
> call_used)
>  	      if (fixed == 0)
>  		call_really_used_regs[i] = call_used;
>  #endif
> +	      user_set_call_save_regs[i] = 1;
>  	    }
>  	}
>      }
> diff --git a/gcc/testsuite/gcc.target/arm/fcall-save-rhigh.c
> b/gcc/testsuite/gcc.target/arm/fcall-save-rhigh.c
> new file mode 100644
> index 0000000..a321a2b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/arm/fcall-save-rhigh.c
> @@ -0,0 +1,10 @@
> +/* { dg-do compile } */
> +/* { dg-final { scan-assembler "mov\\s+r.\\s*,\\s*r8" } } */
> +/* { dg-require-effective-target arm_thumb1_ok } */
> +/* { dg-options "-Os -mthumb -mcpu=cortex-m0 -fcall-saved-r8" } */
> +
> +void
> +save_regs (void)
> +{
> +  asm volatile ("" ::: "r7", "r8");
> +}
> 
> Ok for trunk?
> 
> Best regards,
> 
> Thomas
> 
>