[PATCH] rtl-optimization/110587 - remove quadratic regno_in_use_p

[PATCH] rtl-optimization/110587 - remove quadratic regno_in_use_p

[Richard Biener]

The following removes the code checking whether a noop copy
is between something involved in the return sequence composed
of a SET and USE.  Instead of checking for this special-case
the following makes us only ever remove noop copies between
pseudos - which is the case that is necessary for IRA/LRA
interfacing to function according to the comment.  That makes
looking for the return reg special case unnecessary, reducing
the compile-time in LRA non-specific to zero for the testcase.

Bootstrapped and tested on x86_64-unknown-linux-gnu with
all languages and {,-m32}.

OK?

Thanks,
Richard.

	PR rtl-optimization/110587
	* lra-spills.cc (return_regno_p): Remove.
	(regno_in_use_p): Likewise.
	(lra_final_code_change): Do not remove noop moves
	between hard registers.
---
 gcc/lra-spills.cc | 69 +----------------------------------------------
 1 file changed, 1 insertion(+), 68 deletions(-)

diff --git a/gcc/lra-spills.cc b/gcc/lra-spills.cc
index 3a7bb7e8cd9..fe58f162d05 100644
--- a/gcc/lra-spills.cc
+++ b/gcc/lra-spills.cc
@@ -705,72 +705,6 @@ alter_subregs (rtx *loc, bool final_p)
   return res;
 }
 
-/* Return true if REGNO is used for return in the current
-   function.  */
-static bool
-return_regno_p (unsigned int regno)
-{
-  rtx outgoing = crtl->return_rtx;
-
-  if (! outgoing)
-    return false;
-
-  if (REG_P (outgoing))
-    return REGNO (outgoing) == regno;
-  else if (GET_CODE (outgoing) == PARALLEL)
-    {
-      int i;
-
-      for (i = 0; i < XVECLEN (outgoing, 0); i++)
-	{
-	  rtx x = XEXP (XVECEXP (outgoing, 0, i), 0);
-
-	  if (REG_P (x) && REGNO (x) == regno)
-	    return true;
-	}
-    }
-  return false;
-}
-
-/* Return true if REGNO is in one of subsequent USE after INSN in the
-   same BB.  */
-static bool
-regno_in_use_p (rtx_insn *insn, unsigned int regno)
-{
-  static lra_insn_recog_data_t id;
-  static struct lra_static_insn_data *static_id;
-  struct lra_insn_reg *reg;
-  int i, arg_regno;
-  basic_block bb = BLOCK_FOR_INSN (insn);
-
-  while ((insn = next_nondebug_insn (insn)) != NULL_RTX)
-    {
-      if (BARRIER_P (insn) || bb != BLOCK_FOR_INSN (insn))
-	return false;
-      if (! INSN_P (insn))
-	continue;
-      if (GET_CODE (PATTERN (insn)) == USE
-	  && REG_P (XEXP (PATTERN (insn), 0))
-	  && regno == REGNO (XEXP (PATTERN (insn), 0)))
-	return true;
-      /* Check that the regno is not modified.  */
-      id = lra_get_insn_recog_data (insn);
-      for (reg = id->regs; reg != NULL; reg = reg->next)
-	if (reg->type != OP_IN && reg->regno == (int) regno)
-	  return false;
-      static_id = id->insn_static_data;
-      for (reg = static_id->hard_regs; reg != NULL; reg = reg->next)
-	if (reg->type != OP_IN && reg->regno == (int) regno)
-	  return false;
-      if (id->arg_hard_regs != NULL)
-	for (i = 0; (arg_regno = id->arg_hard_regs[i]) >= 0; i++)
-	  if ((int) regno == (arg_regno >= FIRST_PSEUDO_REGISTER
-			      ? arg_regno : arg_regno - FIRST_PSEUDO_REGISTER))
-	    return false;
-    }
-  return false;
-}
-
 /* Final change of pseudos got hard registers into the corresponding
    hard registers and removing temporary clobbers.  */
 void
@@ -821,8 +755,7 @@ lra_final_code_change (void)
 	  if (NONJUMP_INSN_P (insn) && GET_CODE (pat) == SET
 	      && REG_P (SET_SRC (pat)) && REG_P (SET_DEST (pat))
 	      && REGNO (SET_SRC (pat)) == REGNO (SET_DEST (pat))
-	      && (! return_regno_p (REGNO (SET_SRC (pat)))
-		  || ! regno_in_use_p (insn, REGNO (SET_SRC (pat)))))
+	      && REGNO (SET_SRC (pat)) >= FIRST_PSEUDO_REGISTER)
 	    {
 	      lra_invalidate_insn_data (insn);
 	      delete_insn (insn);
-- 
2.35.3

Re: [PATCH] rtl-optimization/110587 - remove quadratic regno_in_use_p

[Vladimir Makarov]

On 7/25/23 09:40, Richard Biener wrote:
> The following removes the code checking whether a noop copy
> is between something involved in the return sequence composed
> of a SET and USE.  Instead of checking for this special-case
> the following makes us only ever remove noop copies between
> pseudos - which is the case that is necessary for IRA/LRA
> interfacing to function according to the comment.  That makes
> looking for the return reg special case unnecessary, reducing
> the compile-time in LRA non-specific to zero for the testcase.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu with
> all languages and {,-m32}.
>
> OK?
>
Richard, sorry for the delay with the answer.  I was on vacation.

There is a lot of history of changes of the code.  I believe your change 
is right.  I don't think that RTL will ever contain noop return move 
insn involving the return hard register especially after removing hard 
reg propagation couple years ago, at least IRA/LRA do not generate such 
insns during its work.

So the patch is OK for me.  I specially like that the big part of code 
is removed.  No code, no problem (including performance one).  Thank you 
for the patch.

> 	PR rtl-optimization/110587
> 	* lra-spills.cc (return_regno_p): Remove.
> 	(regno_in_use_p): Likewise.
> 	(lra_final_code_change): Do not remove noop moves
> 	between hard registers.
> ---
>   gcc/lra-spills.cc | 69 +----------------------------------------------
>   1 file changed, 1 insertion(+), 68 deletions(-)
>
> diff --git a/gcc/lra-spills.cc b/gcc/lra-spills.cc
> index 3a7bb7e8cd9..fe58f162d05 100644
> --- a/gcc/lra-spills.cc
> +++ b/gcc/lra-spills.cc
> @@ -705,72 +705,6 @@ alter_subregs (rtx *loc, bool final_p)
>     return res;
>   }

Re: [PATCH] rtl-optimization/110587 - remove quadratic regno_in_use_p

[Jeff Law]

On 7/31/23 04:53, Richard Biener via Gcc-patches wrote:
> On Tue, 25 Jul 2023, Richard Biener wrote:
> 
>> The following removes the code checking whether a noop copy
>> is between something involved in the return sequence composed
>> of a SET and USE.  Instead of checking for this special-case
>> the following makes us only ever remove noop copies between
>> pseudos - which is the case that is necessary for IRA/LRA
>> interfacing to function according to the comment.  That makes
>> looking for the return reg special case unnecessary, reducing
>> the compile-time in LRA non-specific to zero for the testcase.
>>
>> Bootstrapped and tested on x86_64-unknown-linux-gnu with
>> all languages and {,-m32}.
>>
>> OK?
> 
> Ping.
> 
>> Thanks,
>> Richard.
>>
>> 	PR rtl-optimization/110587
>> 	* lra-spills.cc (return_regno_p): Remove.
>> 	(regno_in_use_p): Likewise.
>> 	(lra_final_code_change): Do not remove noop moves
>> 	between hard registers.
OK
jeff

Re: [PATCH] rtl-optimization/110587 - remove quadratic regno_in_use_p

[Richard Biener]

On Tue, 25 Jul 2023, Richard Biener wrote:

> The following removes the code checking whether a noop copy
> is between something involved in the return sequence composed
> of a SET and USE.  Instead of checking for this special-case
> the following makes us only ever remove noop copies between
> pseudos - which is the case that is necessary for IRA/LRA
> interfacing to function according to the comment.  That makes
> looking for the return reg special case unnecessary, reducing
> the compile-time in LRA non-specific to zero for the testcase.
> 
> Bootstrapped and tested on x86_64-unknown-linux-gnu with
> all languages and {,-m32}.
> 
> OK?

Ping.

> Thanks,
> Richard.
> 
> 	PR rtl-optimization/110587
> 	* lra-spills.cc (return_regno_p): Remove.
> 	(regno_in_use_p): Likewise.
> 	(lra_final_code_change): Do not remove noop moves
> 	between hard registers.
> ---
>  gcc/lra-spills.cc | 69 +----------------------------------------------
>  1 file changed, 1 insertion(+), 68 deletions(-)
> 
> diff --git a/gcc/lra-spills.cc b/gcc/lra-spills.cc
> index 3a7bb7e8cd9..fe58f162d05 100644
> --- a/gcc/lra-spills.cc
> +++ b/gcc/lra-spills.cc
> @@ -705,72 +705,6 @@ alter_subregs (rtx *loc, bool final_p)
>    return res;
>  }
>  
> -/* Return true if REGNO is used for return in the current
> -   function.  */
> -static bool
> -return_regno_p (unsigned int regno)
> -{
> -  rtx outgoing = crtl->return_rtx;
> -
> -  if (! outgoing)
> -    return false;
> -
> -  if (REG_P (outgoing))
> -    return REGNO (outgoing) == regno;
> -  else if (GET_CODE (outgoing) == PARALLEL)
> -    {
> -      int i;
> -
> -      for (i = 0; i < XVECLEN (outgoing, 0); i++)
> -	{
> -	  rtx x = XEXP (XVECEXP (outgoing, 0, i), 0);
> -
> -	  if (REG_P (x) && REGNO (x) == regno)
> -	    return true;
> -	}
> -    }
> -  return false;
> -}
> -
> -/* Return true if REGNO is in one of subsequent USE after INSN in the
> -   same BB.  */
> -static bool
> -regno_in_use_p (rtx_insn *insn, unsigned int regno)
> -{
> -  static lra_insn_recog_data_t id;
> -  static struct lra_static_insn_data *static_id;
> -  struct lra_insn_reg *reg;
> -  int i, arg_regno;
> -  basic_block bb = BLOCK_FOR_INSN (insn);
> -
> -  while ((insn = next_nondebug_insn (insn)) != NULL_RTX)
> -    {
> -      if (BARRIER_P (insn) || bb != BLOCK_FOR_INSN (insn))
> -	return false;
> -      if (! INSN_P (insn))
> -	continue;
> -      if (GET_CODE (PATTERN (insn)) == USE
> -	  && REG_P (XEXP (PATTERN (insn), 0))
> -	  && regno == REGNO (XEXP (PATTERN (insn), 0)))
> -	return true;
> -      /* Check that the regno is not modified.  */
> -      id = lra_get_insn_recog_data (insn);
> -      for (reg = id->regs; reg != NULL; reg = reg->next)
> -	if (reg->type != OP_IN && reg->regno == (int) regno)
> -	  return false;
> -      static_id = id->insn_static_data;
> -      for (reg = static_id->hard_regs; reg != NULL; reg = reg->next)
> -	if (reg->type != OP_IN && reg->regno == (int) regno)
> -	  return false;
> -      if (id->arg_hard_regs != NULL)
> -	for (i = 0; (arg_regno = id->arg_hard_regs[i]) >= 0; i++)
> -	  if ((int) regno == (arg_regno >= FIRST_PSEUDO_REGISTER
> -			      ? arg_regno : arg_regno - FIRST_PSEUDO_REGISTER))
> -	    return false;
> -    }
> -  return false;
> -}
> -
>  /* Final change of pseudos got hard registers into the corresponding
>     hard registers and removing temporary clobbers.  */
>  void
> @@ -821,8 +755,7 @@ lra_final_code_change (void)
>  	  if (NONJUMP_INSN_P (insn) && GET_CODE (pat) == SET
>  	      && REG_P (SET_SRC (pat)) && REG_P (SET_DEST (pat))
>  	      && REGNO (SET_SRC (pat)) == REGNO (SET_DEST (pat))
> -	      && (! return_regno_p (REGNO (SET_SRC (pat)))
> -		  || ! regno_in_use_p (insn, REGNO (SET_SRC (pat)))))
> +	      && REGNO (SET_SRC (pat)) >= FIRST_PSEUDO_REGISTER)
>  	    {
>  	      lra_invalidate_insn_data (insn);
>  	      delete_insn (insn);
>