| Message ID | alpine.LNX.2.00.1202061432350.4999@zhemvz.fhfr.qr |
|---|---|
| State | New |
| Headers | show |
Index: gcc/tree-ssa-loop-ivopts.c =================================================================== --- gcc/tree-ssa-loop-ivopts.c (revision 183757) +++ gcc/tree-ssa-loop-ivopts.c (working copy) @@ -4048,7 +4048,11 @@ get_computation_cost_at (struct ivopts_d return infinite_cost; } - if (address_p) + if (address_p + || (use->iv->base_object + && cand->iv->base_object + && POINTER_TYPE_P (TREE_TYPE (use->iv->base_object)) + && POINTER_TYPE_P (TREE_TYPE (cand->iv->base_object)))) { /* Do not try to express address of an object with computation based on address of a different object. This may cause problems in rtl
This fixes PR50955 - IVOPTs can end up expressing a pointer value using unrelated pointer bases. This confuses alias analysis. The fix is to extend the existing stop-gap we have in place to cover the case in question. Bootstrapped and tested on x86_64-unknonw-linux-gnu. I have also benchmarked the patch on SPEC 2k6 and SPEC 2k (both 64bit and 32bit codegen) with only a single visible regression at 64bit 191.fma32 at -O2 -ffast-math (-O3 -ffast-math is fine). The patch shows small consistent wins on 32bit SPEC 2k when using SSE math. Committed to trunk. Richard. 2012-02-06 Richard Guenther <rguenther@suse.de> PR tree-optimization/50955 * tree-ssa-loop-ivopts.c (get_computation_cost_at): Artificially raise cost of expressions that replace an address with an expression based on a different pointer.