Re: [PATCH v2 2/2] aarch64: Lower vcombine to GIMPLE

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

Andrew Carlotti <andrew.carlotti@arm.com> writes:
> This lowers vcombine intrinsics to a GIMPLE vector constructor, which enables
> better optimisation during GIMPLE passes.
>
> gcc/
>
> 	* config/aarch64/aarch64-builtins.c
> 	(aarch64_general_gimple_fold_builtin): Add combine.
>
> gcc/testsuite/
>
> 	* gcc.target/aarch64/advsimd-intrinsics/combine.c:
> 	New test.
>
> diff --git a/gcc/config/aarch64/aarch64-builtins.cc b/gcc/config/aarch64/aarch64-builtins.cc
> index 5753988a9964967c27a03aca5fddb9025fd8ed6e..a25756cfed5fab3a98ebf3e2ee29a5e117cbd2aa 100644
> --- a/gcc/config/aarch64/aarch64-builtins.cc
> +++ b/gcc/config/aarch64/aarch64-builtins.cc
> @@ -2857,6 +2857,28 @@ aarch64_general_gimple_fold_builtin (unsigned int fcode, gcall *stmt,
>  	gimple_call_set_lhs (new_stmt, gimple_call_lhs (stmt));
>  	break;
>  
> +     BUILTIN_VDC (BINOP, combine, 0, AUTO_FP)
> +     BUILTIN_VD_I (BINOPU, combine, 0, NONE)
> +     BUILTIN_VDC_P (BINOPP, combine, 0, NONE)
> +	{
> +	  tree first_part, second_part;
> +	  if (BYTES_BIG_ENDIAN)
> +	    {
> +	      second_part = args[0];
> +	      first_part = args[1];
> +	    }
> +	  else
> +	    {
> +	      first_part = args[0];
> +	      second_part = args[1];
> +	    }
> +	  tree ret_type = TREE_TYPE (gimple_call_lhs (stmt));

Just repeating what we discussed off-list for the record: this needs
to be gimple_call_return_type.  LGTM with that change.

Thanks,
Richard

> +	  tree ctor = build_constructor_va (ret_type, 2, NULL_TREE, first_part,
> +					    NULL_TREE, second_part);
> +	  new_stmt = gimple_build_assign (gimple_call_lhs (stmt), ctor);
> +	}
> +	break;
> +
>       /*lower store and load neon builtins to gimple.  */
>       BUILTIN_VALL_F16 (LOAD1, ld1, 0, LOAD)
>       BUILTIN_VDQ_I (LOAD1_U, ld1, 0, LOAD)
> diff --git a/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/combine.c b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/combine.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..d08faf7a4a160a1e83428ed9b270731bbf7b8c8a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/combine.c
> @@ -0,0 +1,18 @@
> +/* { dg-do compile { target { aarch64*-*-* } } } */
> +/* { dg-final { check-function-bodies "**" "" {-O[^0]} } } */
> +/* { dg-skip-if "" { *-*-* } { "-fno-fat-lto-objects" } } */
> +
> +#include <arm_neon.h>
> +
> +/*
> +** foo:
> +**	umov	w0, v1\.s\[1\]
> +**	ret
> +*/
> +
> +int32_t foo (int32x2_t a, int32x2_t b)
> +{
> +  int32x4_t c = vcombine_s32(a, b);
> +  return vgetq_lane_s32(c, 3);
> +}
> +