Hi.

This fixes some implementations mistakes in sbitmap.c (bitmap_bit_in_range_p). There's reference
to implementation one can take inspiration from:
https://www.cs.umd.edu/class/sum2003/cmsc311/Notes/BitOp/bitRange.html

Problem with our implementation is that one can't do:
(SBITMAP_ELT_TYPE)1 << SBITMAP_ELT_BITS (that would overflow)
Thus I do conditionally ~(SBITMAP_ELT_TYPE)0 at some places in the code.

I also added quite some unit tests for the method. But another questions pop up:
1) there are missing boundary asserts (or checking asserts) in sbitmap.c
2) we should probably include test-cases also for other functions

I can work on that (probably later) if desired?

And my patch breaks ssa-dse-26.c test-case, because now it properly returns true for:

#0  bitmap_bit_in_range_p (bmap=0x21c4940, start=0, end=8) at ../../gcc/sbitmap.c:326
#1  0x0000000000d618f5 in live_bytes_read (use_ref=..., ref=0x7fffffffd480, live=0x21c4940) at ../../gcc/tree-ssa-dse.c:496
#2  0x0000000000d61c4d in dse_classify_store (ref=0x7fffffffd480, stmt=0x155553ea7d70, use_stmt=0x7fffffffd470, byte_tracking_enabled=true, live_bytes=0x21c4940) at ../../gcc/tree-ssa-dse.c:594
#3  0x0000000000d6235b in dse_dom_walker::dse_optimize_stmt (this=0x7fffffffd5c0, gsi=0x7fffffffd530) at ../../gcc/tree-ssa-dse.c:820
#4  0x0000000000d62461 in dse_dom_walker::before_dom_children (this=0x7fffffffd5c0, bb=0x155553d76270) at ../../gcc/tree-ssa-dse.c:852
#5  0x00000000013b1698 in dom_walker::walk (this=0x7fffffffd5c0, bb=0x155553d76270) at ../../gcc/domwalk.c:308
#6  0x0000000000d625ac in (anonymous namespace)::pass_dse::execute (this=0x21d58c0, fun=0x155553eac0b0) at ../../gcc/tree-ssa-dse.c:906
#7  0x0000000000b27441 in execute_one_pass (pass=pass@entry=0x21d58c0) at ../../gcc/passes.c:2495
#8  0x0000000000b27d01 in execute_pass_list_1 (pass=0x21d58c0) at ../../gcc/passes.c:2584
#9  0x0000000000b27d13 in execute_pass_list_1 (pass=0x21d5480) at ../../gcc/passes.c:2585
#10 0x0000000000b27d55 in execute_pass_list (fn=<optimized out>, pass=<optimized out>) at ../../gcc/passes.c:2595
#11 0x0000000000b26681 in do_per_function_toporder (callback=callback@entry=0xb27d40 <execute_pass_list(function*, opt_pass*)>, data=0x21d5300) at ../../gcc/passes.c:1737
#12 0x0000000000b283d7 in execute_ipa_pass_list (pass=0x21d52a0) at ../../gcc/passes.c:2935
#13 0x00000000007d29d2 in ipa_passes () at ../../gcc/cgraphunit.c:2399
#14 symbol_table::compile (this=this@entry=0x155553d6e100) at ../../gcc/cgraphunit.c:2534
#15 0x00000000007d5277 in symbol_table::compile (this=0x155553d6e100) at ../../gcc/cgraphunit.c:2695
#16 symbol_table::finalize_compilation_unit (this=0x155553d6e100) at ../../gcc/cgraphunit.c:2692
#17 0x0000000000c118ac in compile_file () at ../../gcc/toplev.c:481
#18 0x0000000000c13eee in do_compile () at ../../gcc/toplev.c:2037
#19 0x0000000000c141da in toplev::main (this=0x7fffffffd85e, argc=21, argv=0x7fffffffd958) at ../../gcc/toplev.c:2172
#20 0x000000000061aeab in main (argc=21, argv=0x7fffffffd958) at ../../gcc/main.c:39

(gdb) p debug(bmap)
n_bits = 256, set = {8 9 10 11 12 13 14 15 }

Jeff can you please help me?
Apart from that the patch can bootstrap on ppc64le-redhat-linux and survives regression tests.

Ready to be installed?
Martin

Thanks,
Martin

gcc/ChangeLog:

2017-10-10  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/82493
	* sbitmap.c (bitmap_bit_in_range_p): Fix the implementation.
	(test_range_functions): New function.
	(sbitmap_c_tests): Likewise.
	* selftest-run-tests.c (selftest::run_tests): Run new tests.
	* selftest.h (sbitmap_c_tests): New function.
---
 gcc/sbitmap.c            | 118 ++++++++++++++++++++++++++++++++++++++++-------
 gcc/selftest-run-tests.c |   1 +
 gcc/selftest.h           |   1 +
 3 files changed, 103 insertions(+), 17 deletions(-)