[PATCH] Simplify floating point comparisons

[Jeff Law]

On 01/12/2018 06:21 AM, Wilco Dijkstra wrote:
> Hi,
> 
> Here is the updated version:
> 
> This patch implements some of the optimizations discussed in
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71026.
> 
> Simplify (C / x >= 0.0) into x >= 0.0 with -fno-signed-zeros
> and -ffinite-math-only.  If C is negative the comparison is reversed.
> Only handle >= and <= for now since C / x can underflow if C is small.
> 
> 
> Simplify (x * C1) > C2 into x > (C2 / C1) with -funsafe-math-optimizations.
> If C1 is negative the comparison is reversed.
> 
> OK for commit?
> 
> ChangeLog
> 2018-01-10  Wilco Dijkstra  <wdijkstr@arm.com>  
> 	    Jackson Woodruff  <jackson.woodruff@arm.com>
> 
>     gcc/
> 	PR 71026/tree-optimization
> 	* match.pd: Simplify floating point comparisons.
> 
>     gcc/testsuite/
> 	PR 71026/tree-optimization
> 	* gcc.dg/div-cmp-1.c: New test.
> 	* gcc.dg/div-cmp-2.c: New test.
OK for the trunk.  I don't think there is a need to backport to gcc-8.

jeff