On Tue, Feb 14, 2017 at 2:48 PM, Richard Biener <rguent...@suse.de> wrote:
>
> The following enables final value replacement for floating point
> expressions if -funsafe-math-optimizations is set (that's the
> flag the reassoc pass controls similar transforms on).
Looks to me it's kind of abusing of current implementation of SCEV for
floating point values. I believe it's designed only with integral
type in mind, for example, we may need to reject float time when
tracking scev chain via type conversion.
Thanks,
bin
>
> Bootstrapped / tested on x86_64-unknown-linux-gnu, queued for GCC 8.
>
> Richard.
>
> 2017-02-14 Richard Biener <rguent...@suse.de>
>
> PR tree-optimization/79460
> * tree-scalar-evolution.c (final_value_replacement_loop): Also
> allow final value replacement of floating point expressions.
>
> * gcc.dg/tree-ssa/sccp-3.c: New testcase.
>
> Index: gcc/tree-scalar-evolution.c
> ===================================================================
> --- gcc/tree-scalar-evolution.c (revision 245417)
> +++ gcc/tree-scalar-evolution.c (working copy)
> @@ -3718,8 +3718,10 @@ final_value_replacement_loop (struct loo
> continue;
> }
>
> - if (!POINTER_TYPE_P (TREE_TYPE (def))
> - && !INTEGRAL_TYPE_P (TREE_TYPE (def)))
> + if (! (POINTER_TYPE_P (TREE_TYPE (def))
> + || INTEGRAL_TYPE_P (TREE_TYPE (def))
> + || (FLOAT_TYPE_P (TREE_TYPE (def))
> + && flag_unsafe_math_optimizations)))
> {
> gsi_next (&psi);
> continue;
> Index: gcc/testsuite/gcc.dg/tree-ssa/sccp-3.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/sccp-3.c (nonexistent)
> +++ gcc/testsuite/gcc.dg/tree-ssa/sccp-3.c (working copy)
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -funsafe-math-optimizations -fdump-tree-sccp" } */
> +
> +float f(float x[])
> +{
> + float p = 1.0;
> + for (int i = 0; i < 200; i++)
> + p += 1;
> + return p;
> +}
> +
> +/* { dg-final { scan-tree-dump "final value replacement.* = 2.01e\\+2;"
> "sccp" } } */
