On Tue, 8 Aug 2017, Bin.Cheng wrote:
> On Tue, Aug 8, 2017 at 1:20 PM, Richard Biener <rguent...@suse.de> wrote:
> >
> > The following improves niter analysis for range-based for loops
> > by handling ADDR_EXPR in expand_simple_operations.
> >
> > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
> >
> > Richard.
> >
> > 2017-08-08 Richard Biener <rguent...@suse.de>
> >
> > PR middle-end/81719
> > * tree-ssa-loop-niter.c: Include tree-dfa.h.
> > (expand_simple_operations): Also look through ADDR_EXPRs with
> > MEM_REF bases treating them as POINTER_PLUS_EXPR.
> >
> > * g++.dg/tree-ssa/pr81719.C: New testcase.
> >
> > Index: gcc/tree-ssa-loop-niter.c
> > ===================================================================
> > *** gcc/tree-ssa-loop-niter.c (revision 250813)
> > --- gcc/tree-ssa-loop-niter.c (working copy)
> > *************** along with GCC; see the file COPYING3.
> > *** 42,47 ****
> > --- 42,48 ----
> > #include "tree-chrec.h"
> > #include "tree-scalar-evolution.h"
> > #include "params.h"
> > + #include "tree-dfa.h"
> >
> >
> > /* The maximum number of dominator BBs we search for conditions
> > *************** expand_simple_operations (tree expr, tre
> > *** 1980,1985 ****
> > --- 1981,2001 ----
> >
> > if (code == SSA_NAME)
> > return expand_simple_operations (e, stop);
> > + else if (code == ADDR_EXPR)
> > + {
> > + HOST_WIDE_INT offset;
> > + tree base = get_addr_base_and_unit_offset (TREE_OPERAND (e, 0),
> > + &offset);
> > + if (base
> > + && TREE_CODE (base) == MEM_REF)
> > + {
> > + ee = expand_simple_operations (TREE_OPERAND (base, 0), stop);
> > + return fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (expr), ee,
> > + wide_int_to_tree (sizetype,
> > + mem_ref_offset (base)
> > + + offset));
> > + }
> > + }
> >
> > return expr;
> > }
> There are various places we need to look into ADDR_EXPR (MEM_REF), is
> it possible/beneficial to generally simplify &MEM_REF[base + offset]?
Not sure - we already do this to some extent in pass_laddress, but
only for the non-constant offset case.
Note for the testcase we have &MEM[ptr + 8] and &ptr->foo.bar.
Richard.
> Thanks,
> bin
> > Index: gcc/testsuite/g++.dg/tree-ssa/pr81719.C
> > ===================================================================
> > *** gcc/testsuite/g++.dg/tree-ssa/pr81719.C (nonexistent)
> > --- gcc/testsuite/g++.dg/tree-ssa/pr81719.C (working copy)
> > ***************
> > *** 0 ****
> > --- 1,24 ----
> > + /* { dg-do compile { target c++11 } } */
> > + /* { dg-options "-O3 -fdump-tree-optimized" } */
> > +
> > + typedef int Items[2];
> > +
> > + struct ItemArray
> > + {
> > + Items items;
> > + int sum_x2() const;
> > + };
> > +
> > + int ItemArray::sum_x2() const
> > + {
> > + int total = 0;
> > + for (int item : items)
> > + {
> > + total += item;
> > + }
> > + return total;
> > + }
> > +
> > + /* We should be able to compute the number of iterations to two, unroll
> > + the loop and end up with a single basic-block in sum_x2. */
> > + /* { dg-final { scan-tree-dump-times "bb" 1 "optimized" } } */
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
