Re: [11/32] Remove global call sets: cse.c

[Jeff Law <law@redhat.com>]

On 9/25/19 9:57 AM, Richard Sandiford wrote:
> Richard Sandiford <richard.sandiford@arm.com> writes:
>> Like with the combine.c patch, this one keeps things simple by
>> invalidating values in partially-clobbered registers, rather than
>> trying to tell whether the value in a partially-clobbered register
>> is actually clobbered or not.  Again, this is in principle a bug fix,
>> but probably never matters in practice.
> 
> Similary to the combine patch, I've updated this to avoid the
> short "abi" name and use a temporary HARD_REG_SET instead.
> 
> Richard
> 
> 
> 2019-09-25  Richard Sandiford  <richard.sandiford@arm.com>
> 
> gcc/
> 	* cse.c: Include regs.h and function-abi.h.
> 	(invalidate_for_call): Take the call insn as an argument.
> 	Use insn_callee_abi to get the ABI of the call and invalidate
> 	partially clobbered registers as well as fully clobbered ones.
> 	(cse_insn): Update call accordingly.
> 
> Index: gcc/cse.c
> ===================================================================
> --- gcc/cse.c	2019-09-17 15:27:11.338066929 +0100
> +++ gcc/cse.c	2019-09-25 16:55:31.202641509 +0100
> @@ -42,6 +42,8 @@ Software Foundation; either version 3, o
>  #include "tree-pass.h"
>  #include "dbgcnt.h"
>  #include "rtl-iter.h"
> +#include "regs.h"
> +#include "function-abi.h"
>  
>  /* The basic idea of common subexpression elimination is to go
>     through the code, keeping a record of expressions that would
> @@ -566,7 +568,6 @@ static void remove_invalid_subreg_refs (
>  					machine_mode);
>  static void rehash_using_reg (rtx);
>  static void invalidate_memory (void);
> -static void invalidate_for_call (void);
>  static rtx use_related_value (rtx, struct table_elt *);
>  
>  static inline unsigned canon_hash (rtx, machine_mode);
> @@ -2091,23 +2092,29 @@ rehash_using_reg (rtx x)
>  }
>  \f
>  /* Remove from the hash table any expression that is a call-clobbered
> -   register.  Also update their TICK values.  */
> +   register in INSN.  Also update their TICK values.  */
>  
>  static void
> -invalidate_for_call (void)
> +invalidate_for_call (rtx_insn *insn)
>  {
> -  unsigned int regno, endregno;
> -  unsigned int i;
> +  unsigned int regno;
>    unsigned hash;
>    struct table_elt *p, *next;
>    int in_table = 0;
>    hard_reg_set_iterator hrsi;
>  
> -  /* Go through all the hard registers.  For each that is clobbered in
> -     a CALL_INSN, remove the register from quantity chains and update
> +  /* Go through all the hard registers.  For each that might be clobbered
> +     in call insn INSN, remove the register from quantity chains and update
>       reg_tick if defined.  Also see if any of these registers is currently
> -     in the table.  */
> -  EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call, 0, regno, hrsi)
> +     in the table.
> +
> +     ??? We could be more precise for partially-clobbered registers,
> +     and only invalidate values that actually occupy the clobbered part
> +     of the registers.  It doesn't seem worth the effort though, since
> +     we shouldn't see this situation much before RA.  */
> +  HARD_REG_SET callee_clobbers
> +    = insn_callee_abi (insn).full_and_partial_reg_clobbers ();
> +  EXECUTE_IF_SET_IN_HARD_REG_SET (callee_clobbers, 0, regno, hrsi)
>      {
>        delete_reg_equiv (regno);
>        if (REG_TICK (regno) >= 0)
> @@ -2132,15 +2139,11 @@ invalidate_for_call (void)
>  	      || REGNO (p->exp) >= FIRST_PSEUDO_REGISTER)
>  	    continue;
>  
> -	  regno = REGNO (p->exp);
> -	  endregno = END_REGNO (p->exp);
> -
> -	  for (i = regno; i < endregno; i++)
> -	    if (TEST_HARD_REG_BIT (regs_invalidated_by_call, i))
> -	      {
> -		remove_from_table (p, hash);
> -		break;
> -	      }
> +	  /* This must use the same test as above rather than the
> +	     more accurate clobbers_reg_p.  */
> +	  if (overlaps_hard_reg_set_p (callee_clobbers, GET_MODE (p->exp),
> +				       REGNO (p->exp)))
Is it worth putting a forward comment to the earlier test to the later
one to help ensure they're kept in sync?

OK with or without that comment update.