Hello,
Thank you for the review
On 5/28/26 5:36 PM, Jeffrey Law wrote:
So we very much want to look through those conversions and use the
narrower range. But it seems like ranger should have associated the
narrower range with output SSA_NAME for those conversions and we
should have been using that output SSA_NAME rather chasing things down
through a CONVERT_EXPR.
So I guess the question is how do we get a CONVERT_EXPR in here rather
than an SSA_NAME? That may point to a cleaner solution.
jeff
The CONVERT_EXPR comes from the existing call to
expand_simple_operations in number_of_iterations_exit_assumptions:
iv0.base = expand_simple_operations (iv0.base);
iv1.base = expand_simple_operations (iv1.base);
expand_simple_operations treats casts as simple operations, so in this
case the SSA_NAME for the converted value has already been expanded back
into a CONVERT_EXPR by the time determine_value_range sees it.
I did try avoiding this expansion, and also tried changing
expand_simple_operations to return the original SSA_NAME for this case.
Both approaches caused regressions in cunrolli and lsplit, which made the
change seem too broad. Given that expand_simple_operations is used by
niter analysis to expose simple operations in bounds, handling
value-preserving conversions in determine_value_range seemed like the
more localized fix.
That said, I may be missing a cleaner place to recover the range of the
converted SSA_NAME. If you think there is a better point to do this, I’m
happy to rework the patch in that direction.
Thanks,
Abhishek
