id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
4276	-O0 runs in constant space, -O1 and -O2 don't	guest	igloo	"Enabling optimization changes the space complexity of this small program, which seems like a bug.  Run the attached program with command line argument equal to 22 or greater.

Description of the program: given a real valued function f, compute the sum f(x_i) over an increasingly finer and finer mesh of sample points.   If the new mesh shares points with the old mesh this can be computed somewhat more efficiently by reusing the previous sum.  

Looking at the Time and Allocation report, it seems like the optimized versions of the program are actually computing the sum 2 ** n times instead of n times.  This is probably related to what is causing the space behavior. "	bug	closed	normal	7.4.1	Compiler	6.12.1	duplicate	optimization space leak	omarab@… daniel.is.fischer@…	Windows	x86	Runtime performance bug