public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/97555] [11 Regression] wrong code at -Os and above on x86_64-pc-linux-gnu since r11-3685 Date: Mon, 26 Oct 2020 16:57:30 +0000 [thread overview] Message-ID: <bug-97555-4-EBqx56XIE5@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-97555-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97555 --- Comment #4 from Aldy Hernandez <aldyh at gcc dot gnu.org> --- The problem here is we're trying to add 1 to a -1 in a signed 1-bit field. Signed 1-bits are annoying because you can't really add or subtract one, because the one is unrepresentable. For invert() we have a special subtract_one() function that handles 1-bit signed fields. We need a corresponding add_one() here. The untested patch below should do it. diff --git a/gcc/range-op.cc b/gcc/range-op.cc index ee62f103598..74ab2e57fde 100644 --- a/gcc/range-op.cc +++ b/gcc/range-op.cc @@ -3680,15 +3680,28 @@ range_tests () // Test 1-bit signed integer union. // [-1,-1] U [0,0] = VARYING. tree one_bit_type = build_nonstandard_integer_type (1, 0); + tree one_bit_min = vrp_val_min (one_bit_type); + tree one_bit_max = vrp_val_max (one_bit_type); { - tree one_bit_min = vrp_val_min (one_bit_type); - tree one_bit_max = vrp_val_max (one_bit_type); int_range<2> min (one_bit_min, one_bit_min); int_range<2> max (one_bit_max, one_bit_max); max.union_ (min); ASSERT_TRUE (max.varying_p ()); } + // Test inversion of 1-bit signed integers. + { + int_range<2> min (one_bit_min, one_bit_min); + int_range<2> max (one_bit_max, one_bit_max); + int_range<2> t; + t = min; + t.invert (); + ASSERT_TRUE (t == max); + t = max; + t.invert (); + ASSERT_TRUE (t == min); + } + // Test that NOT(255) is [0..254] in 8-bit land. int_range<1> not_255 (UCHAR (255), UCHAR (255), VR_ANTI_RANGE); ASSERT_TRUE (not_255 == int_range<1> (UCHAR (0), UCHAR (254))); diff --git a/gcc/value-range.cc b/gcc/value-range.cc index 7847104050c..f45a342605a 100644 --- a/gcc/value-range.cc +++ b/gcc/value-range.cc @@ -1772,18 +1772,29 @@ irange::irange_intersect (const irange &r) verify_range (); } +// Signed 1-bits are strange. You can't subtract 1, because you can't +// represent the number 1. This works around that for the invert routine. + static wide_int inline subtract_one (const wide_int &x, tree type, wi::overflow_type &overflow) { - // A signed 1-bit bit-field, has a range of [-1,0] so subtracting +1 - // overflows, since +1 is unrepresentable. This is why we have an - // addition of -1 here. if (TYPE_SIGN (type) == SIGNED) - return wi::add (x, -1 , SIGNED, &overflow); + return wi::add (x, -1, SIGNED, &overflow); else return wi::sub (x, 1, UNSIGNED, &overflow); } +// The analogous function for adding 1. + +static wide_int inline +add_one (const wide_int &x, tree type, wi::overflow_type &overflow) +{ + if (TYPE_SIGN (type) == SIGNED) + return wi::sub (x, -1, SIGNED, &overflow); + else + return wi::add (x, 1, TYPE_SIGN (type), &overflow); +} + /* Return the inverse of a range. */ void @@ -1881,7 +1892,7 @@ irange::invert () // set the overflow bit. if (type_max != wi::to_wide (orig_range.m_base[i])) { - tmp = wi::add (wi::to_wide (orig_range.m_base[i]), 1, sign, &ovf); + tmp = add_one (wi::to_wide (orig_range.m_base[i]), ttype, ovf); m_base[nitems++] = wide_int_to_tree (ttype, tmp); m_base[nitems++] = wide_int_to_tree (ttype, type_max); if (ovf)
next prev parent reply other threads:[~2020-10-26 16:57 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-23 19:23 [Bug tree-optimization/97555] New: wrong code at -Os and above on x86_64-pc-linux-gnu su at cs dot ucdavis.edu 2020-10-24 8:15 ` [Bug tree-optimization/97555] [11 Regression] wrong code at -Os and above on x86_64-pc-linux-gnu since r11-3685 jakub at gcc dot gnu.org 2020-10-26 15:58 ` amacleod at redhat dot com 2020-10-26 16:01 ` aldyh at gcc dot gnu.org 2020-10-26 16:57 ` aldyh at gcc dot gnu.org [this message] 2020-10-26 18:06 ` cvs-commit at gcc dot gnu.org 2020-10-26 18:09 ` aldyh at gcc dot gnu.org
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=bug-97555-4-EBqx56XIE5@http.gcc.gnu.org/bugzilla/ \ --to=gcc-bugzilla@gcc.gnu.org \ --cc=gcc-bugs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).