| Message ID | 20230712211528.65888-1-aldyh@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [COMMITTED,range-op] Take known set bits into account in popcount [PR107053] | expand |
On 7/12/23 15:15, Aldy Hernandez via Gcc-patches wrote: > This patch teaches popcount about known set bits which are now > available in the irange. > > PR tree-optimization/107053 > > gcc/ChangeLog: > > * gimple-range-op.cc (cfn_popcount): Use known set bits. > > gcc/testsuite/ChangeLog: > > * gcc.dg/tree-ssa/pr107053.c: New test. You could probably play similar games with ctz/clz, though it's hard to know if it's worth the effort. One way to find out might be to build jemalloc which uses those idioms heavily. Similarly for deepsjeng from spec2017. Jeff
On 7/12/23 23:50, Jeff Law wrote: > > > On 7/12/23 15:15, Aldy Hernandez via Gcc-patches wrote: >> This patch teaches popcount about known set bits which are now >> available in the irange. >> >> PR tree-optimization/107053 >> >> gcc/ChangeLog: >> >> * gimple-range-op.cc (cfn_popcount): Use known set bits. >> >> gcc/testsuite/ChangeLog: >> >> * gcc.dg/tree-ssa/pr107053.c: New test. > You could probably play similar games with ctz/clz, though it's hard to > know if it's worth the effort. > > One way to find out might be to build jemalloc which uses those idioms > heavily. Similarly for deepsjeng from spec2017. > > Jeff > See class cfn_clz and class cfn_ctz in gimple-range-op.cc. There's already code for both of these, although they're throwback from the VRP era, so there's definitely room for improvement. I think they came from vr-values.cc. Aldy
diff --git a/gcc/gimple-range-op.cc b/gcc/gimple-range-op.cc index 72c7b866f90..67b3c3d015e 100644 --- a/gcc/gimple-range-op.cc +++ b/gcc/gimple-range-op.cc @@ -880,17 +880,20 @@ public: if (lh.undefined_p ()) return false; unsigned prec = TYPE_PRECISION (type); - wide_int nz = lh.get_nonzero_bits (); - wide_int pop = wi::shwi (wi::popcount (nz), prec); + irange_bitmask bm = lh.get_bitmask (); + wide_int nz = bm.get_nonzero_bits (); + wide_int high = wi::shwi (wi::popcount (nz), prec); // Calculating the popcount of a singleton is trivial. if (lh.singleton_p ()) { - r.set (type, pop, pop); + r.set (type, high, high); return true; } if (cfn_ffs::fold_range (r, type, lh, rh, rel)) { - int_range<2> tmp (type, wi::zero (prec), pop); + wide_int known_ones = ~bm.mask () & bm.value (); + wide_int low = wi::shwi (wi::popcount (known_ones), prec); + int_range<2> tmp (type, low, high); r.intersect (tmp); return true; } diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr107053.c b/gcc/testsuite/gcc.dg/tree-ssa/pr107053.c new file mode 100644 index 00000000000..8195d0f57b4 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr107053.c @@ -0,0 +1,13 @@ +// { dg-do compile } +// { dg-options "-O2 -fdump-tree-evrp" } + +void link_failure(); +void f(int a) +{ + a |= 0x300; + int b = __builtin_popcount(a); + if (b < 2) + link_failure(); +} + +// { dg-final { scan-tree-dump-not "link_failure" "evrp" } }