public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "gjl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/51374] [avr] insn combine reorders volatile memory accesses Date: Thu, 01 Dec 2011 10:08:00 -0000 [thread overview] Message-ID: <bug-51374-4-1LhA97xQo7@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-51374-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51374 --- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2011-12-01 10:08:05 UTC --- ALso notice, that with the following test case that reads status *after* data typedef unsigned char uint8_t; void __vector_18(void) { unsigned char data = (*(volatile uint8_t *)((0x0C) + 0x20)); unsigned char status = (*(volatile uint8_t *)((0x0B) + 0x20)); static int slot; if (status & 0x10) { if (slot == (-2)) { slot ++; } } } then *no* SBIS/SBIC instruction is produced: __vector_18: in r24,0xc ; 6 movqi_insn/4 [length = 1] in r24,0xb ; 8 movqi_insn/4 [length = 1] sbrs r24,4 ; 11 *sbrx_branchqi [length = 2] rjmp .L1 ... and combine says: Trying 9, 10 -> 11: Successfully matched this instruction: (set (pc) (if_then_else (eq (zero_extract:QI (reg/v:QI 44 [ status ]) (const_int 1 [0x1]) (const_int 4 [0x4])) (const_int 0 [0])) (label_ref:HI 21) (pc))) deferring deletion of insn with uid = 10. deferring deletion of insn with uid = 9. modifying insn i3 11 pc={(zero_extract(r44:QI,0x1,0x4)==0)?L21:pc} REG_DEAD: r44:QI REG_BR_PROB: 0xf3c deferring rescan insn with uid = 11. Trying 8 -> 11: Failed to match this instruction: (set (pc) (if_then_else (eq (zero_extract:QI (mem/v:QI (const_int 43 [0x2b]) [0 MEM[(volatile uint8_t *)43B]+0 S1 A8]) (const_int 1 [0x1]) (const_int 4 [0x4])) (const_int 0 [0])) (label_ref:HI 21) (pc)))
next prev parent reply other threads:[~2011-12-01 10:08 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-12-01 5:01 [Bug c/51374] New: Volatile access reordered andyw at pobox dot com 2011-12-01 9:58 ` [Bug rtl-optimization/51374] [avr] insn combine reorders volatile memory accesses gjl at gcc dot gnu.org 2011-12-01 9:59 ` gjl at gcc dot gnu.org 2011-12-01 10:08 ` gjl at gcc dot gnu.org [this message] 2011-12-01 13:23 ` andyw at pobox dot com 2011-12-08 16:48 ` gjl at gcc dot gnu.org 2011-12-18 20:11 ` gjl at gcc dot gnu.org 2012-01-13 16:00 ` gjl at gcc dot gnu.org 2012-01-13 16:18 ` gjl at gcc dot gnu.org 2012-02-01 11:36 ` gjl at gcc dot gnu.org 2012-02-01 12:41 ` gjl at gcc dot gnu.org 2012-02-01 12:47 ` gjl at gcc dot gnu.org 2012-02-01 12:57 ` gjl 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-51374-4-1LhA97xQo7@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).