Re: [PATCH] simplify-rtx: Fix compare of comparisons (PR60818)

[Segher Boessenkool <segher@kernel.crashing.org>]

Hi!

Is this okay for backport to 5 and 6?


Segher


On Fri, Mar 31, 2017 at 09:40:34PM +0000, Segher Boessenkool wrote:
> The function simplify_binary_operation_1 has code that does
> /* Convert (compare (gt (flags) 0) (lt (flags) 0)) to (flags).  */
> but this transformation is only valid if "flags" has the same machine
> mode as the outer compare.  This fixes it.
> 
> Bootstrapped and tested on powerpc64-linux {-m32,-m64} (and tested the
> new testcase with {-m32,-m64}{,-misel}).  Is this okay for trunk?
> 
> 
> Segher
> 
> 
> 2017-03-31  Segher Boessenkool  <segher@kernel.crashing.org>
> 
> 	PR rtl-optimization/60818
> 	* simplify-rtx.c (simplify_binary_operation_1): Do not replace
> 	a compare of comparisons with the thing compared if this results
> 	in a different machine mode.
> 
> gcc/testsuite/
> 	PR rtl-optimization/60818
> 	* gcc.c-torture/compile/pr60818.c: New testcase.
> 
> ---
>  gcc/simplify-rtx.c                            | 6 +++---
>  gcc/testsuite/gcc.c-torture/compile/pr60818.c | 5 +++++
>  2 files changed, 8 insertions(+), 3 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr60818.c
> 
> diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
> index 3022779..10c2800 100644
> --- a/gcc/simplify-rtx.c
> +++ b/gcc/simplify-rtx.c
> @@ -2367,10 +2367,10 @@
>  	      return xop00;
>  
>  	    if (REG_P (xop00) && REG_P (xop10)
> -		&& GET_MODE (xop00) == GET_MODE (xop10)
>  		&& REGNO (xop00) == REGNO (xop10)
> -		&& GET_MODE_CLASS (GET_MODE (xop00)) == MODE_CC
> -		&& GET_MODE_CLASS (GET_MODE (xop10)) == MODE_CC)
> +		&& GET_MODE (xop00) == mode
> +		&& GET_MODE (xop10) == mode
> +		&& GET_MODE_CLASS (mode) == MODE_CC)
>  	      return xop00;
>  	}
>        break;
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr60818.c b/gcc/testsuite/gcc.c-torture/compile/pr60818.c
> new file mode 100644
> index 0000000..b6171bb
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr60818.c
> @@ -0,0 +1,5 @@
> +int
> +lx (int oi, int mb)
> +{
> +  return (oi < mb) < (mb < oi);
> +}
> -- 
> 1.9.3