middle-end/84407 - honor -frounding-math for int to float conversion

middle-end/84407 - honor -frounding-math for int to float conversion

This makes us honor -frounding-math for integer to float conversions
and avoid constant folding when such conversion is not exact.

2021-10-28  Richard Biener  <rguenther@suse.de>

	PR middle-end/84407
	* fold-const.c (fold_convert_const): Avoid int to float
	constant folding with -frounding-math and inexact result.
	* simplify-rtx.c (simplify_const_unary_operation): Likewise
	for both float and unsigned_float.

	* gcc.dg/torture/fp-uint64-convert-double-1.c: New testcase.
	* gcc.dg/torture/fp-uint64-convert-double-2.c: Likewise.