re PR tree-optimization/72824 (Signed floating point zero semantics broken at optimization level -O3 (tree-loop-distribute-patterns))

	PR tree-optimization/72824
	* tree-loop-distribution.c (const_with_all_bytes_same): Verify
	real_zerop is not negative.

	* gcc.c-torture/execute/ieee/pr72824.c: New test.

From-SVN: r239275