On Thu, 2009-10-08 at 08:49 +0200, Zdenek Dvorak wrote: > Hi, > > > > Ah, indeed. Sorry for being confused. Is tree-niter-desc->assumptions > > > or ->may_be_zero non-NULL? > > > > Yes both. I attached the gdb content for both. > > you need to check may_be_zero, which in your case should contain > something like N <= 49. If this condition is true, the number of > iterations of the loop is zero. Please also check the comments > in tree-flow.h, where the possible outcomes of # of iteration analysis > are explained.
Yes, I already did this: (gdb) call debug_generic_expr (ndesc.assumptions) 1 (gdb) call debug_generic_expr (ndesc.may_be_zero) 0 (gdb) call debug_tree (ndesc.assumptions) <integer_cst 0x29605658 type <boolean_type 0x296145b0 _Bool> constant 1> (gdb) call debug_tree (ndesc.may_be_zero) <integer_cst 0x29605620 type <boolean_type 0x296145b0 _Bool> constant 0> So it seems the "niter" expression should contain the correct solution for every N. The cases where "niter" is not valid are not fullfilled following the description in tree-flow.h Tobias
