Re: [PATCH 2/2]AArch64 Extend tbz pattern to allow SI to SI extensions.

[Richard Sandiford <richard.sandiford@arm.com>]

Tamar Christina <tamar.christina@arm.com> writes:
> Hi All,
>
> This adds additional recognition of & 1 into the tbz/tbnz pattern.
>
> Concretely with the mid-end changes this changes
>
> void g1(bool x)
> {
>   if (__builtin_expect (x, 0))
>     h ();
> }
>
> from
>
>         tst     w0, 255
>         bne     .L7
>
> to
>
>         tbnz    w0, #0, .L5
>
> This pattern occurs ~120,000 times in SPECCPU 20127, basically on
> every boolean comparison.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> 	* config/aarch64/aarch64.md (*tb<optab><mode>1): Renamed this ...
> 	(*tb<optab><GPI2:mode><GPI:mode>1): ... To this.
> 	* config/aarch64/iterators.md (GPI2): New.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.target/aarch64/tbz_1.c: New test.
>
> --- inline copy of patch -- 
> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> index 6aa1fb4be003f2027d63ac69fd314c2bbc876258..3faa03f453c94665d9d82225f180d8afdcd0b5fe 100644
> --- a/gcc/config/aarch64/aarch64.md
> +++ b/gcc/config/aarch64/aarch64.md
> @@ -943,31 +943,33 @@ (define_insn "*cb<optab><mode>1"
>  		      (const_int 1)))]
>  )
>  
> -(define_insn "*tb<optab><mode>1"
> +(define_insn "*tb<optab><GPI2:mode><GPI:mode>1"
>    [(set (pc) (if_then_else
> -	      (EQL (zero_extract:DI (match_operand:GPI 0 "register_operand" "r")
> -				    (const_int 1)
> -				    (match_operand 1
> -				      "aarch64_simd_shift_imm_<mode>" "n"))
> +	      (EQL (zero_extract:GPI2
> +		     (match_operand:GPI 0 "register_operand" "r")
> +		     (const_int 1)
> +		     (match_operand 1 "aarch64_simd_shift_imm_<GPI:mode>" "n"))
>  		   (const_int 0))
>  	     (label_ref (match_operand 2 "" ""))
>  	     (pc)))
>     (clobber (reg:CC CC_REGNUM))]
> -  "!aarch64_track_speculation"
> +  "!aarch64_track_speculation
> +    && known_ge (GET_MODE_SIZE (<GPI2:MODE>mode),
> +		 GET_MODE_SIZE (<GPI:MODE>mode))"

Is this check necessary?  The extraction evaluates to 0 or 1,
so it shouldn't matter whether it is interpreted as DI or SI.

OK without the check if you agree.

Thanks,
Richard

>    {
>      if (get_attr_length (insn) == 8)
>        {
>  	if (get_attr_far_branch (insn) == 1)
>  	  return aarch64_gen_far_branch (operands, 2, "Ltb",
> -					 "<inv_tb>\\t%<w>0, %1, ");
> +					 "<inv_tb>\\t%<GPI:w>0, %1, ");
>  	else
>  	  {
>  	    operands[1] = GEN_INT (HOST_WIDE_INT_1U << UINTVAL (operands[1]));
> -	    return "tst\t%<w>0, %1\;<bcond>\t%l2";
> +	    return "tst\t%<GPI:w>0, %1\;<bcond>\t%l2";
>  	  }
>        }
>      else
> -      return "<tbz>\t%<w>0, %1, %l2";
> +      return "<tbz>\t%<GPI:w>0, %1, %l2";
>    }
>    [(set_attr "type" "branch")
>     (set (attr "length")
> diff --git a/gcc/config/aarch64/iterators.md b/gcc/config/aarch64/iterators.md
> index 89ca66fd291b60a28979785706ecc5345ea86744..f6b2e7a83c63cab73947b6bd61b499b4b57d14ac 100644
> --- a/gcc/config/aarch64/iterators.md
> +++ b/gcc/config/aarch64/iterators.md
> @@ -28,6 +28,8 @@ (define_mode_iterator CCFP_CCFPE [CCFP CCFPE])
>  
>  ;; Iterator for General Purpose Integer registers (32- and 64-bit modes)
>  (define_mode_iterator GPI [SI DI])
> +;; Copy of the above iterator
> +(define_mode_iterator GPI2 [SI DI])
>  
>  ;; Iterator for HI, SI, DI, some instructions can only work on these modes.
>  (define_mode_iterator GPI_I16 [(HI "AARCH64_ISA_F16") SI DI])
> diff --git a/gcc/testsuite/gcc.target/aarch64/tbz_1.c b/gcc/testsuite/gcc.target/aarch64/tbz_1.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..6a75eb4e7aedbfa3ae329358c6ee4d675704a074
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/tbz_1.c
> @@ -0,0 +1,32 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-O2 -std=c99  -fno-unwind-tables -fno-asynchronous-unwind-tables" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target { le } } } } */
> +
> +#include <stdbool.h>// Type your code here, or load an example.
> +
> +void h(void);
> +
> +/*
> +** g1:
> +** 	tbnz	w[0-9], #?0, .L([0-9]+)
> +** 	ret
> +**	...
> +*/
> +void g1(bool x)
> +{
> +  if (__builtin_expect (x, 0))
> +    h ();
> +}
> +
> +/*
> +** g2:
> +** 	tbz	w[0-9]+, #?0, .L([0-9]+)
> +** 	b	h
> +**	...
> +*/
> +void g2(bool x)
> +{
> +  if (__builtin_expect (x, 1))
> +    h ();
> +}
> +