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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/66739] [6 regression] FAIL: gcc.target/aarch64/subs.c scan-assembler subs\tw[0-9]
Date: Mon, 06 Jul 2015 14:39:00 -0000	[thread overview]
Message-ID: <bug-66739-4-ZZwrLDbgls@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-66739-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66739

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
The ppc testcase,

int
f(int a, int b, int c)
{
  a -= (short)b * (c >> 16);
  if (!a)
    return 10;
  return a;
}

is probably artificially triggering the same issue.  Here we do not
test for conditional part but for an instruction used implementing
a -= (short)b * (c >> 16);

But it shows the same issue with the followup transform of sinking the
subtraction to the else path of the if.

I suppose a single-use test is the way to go together with some means to
"override" that when the caller is not going to create the result stmts
but will only perform lookups if the result is already computed (that applies
to all single-use tests).


  parent reply	other threads:[~2015-07-06 14:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-02 12:35 [Bug tree-optimization/66739] New: " schwab@linux-m68k.org
2015-07-02 12:37 ` [Bug tree-optimization/66739] " schwab@linux-m68k.org
2015-07-02 12:42 ` rguenth at gcc dot gnu.org
2015-07-02 12:44 ` rguenth at gcc dot gnu.org
2015-07-05 12:34 ` schwab@linux-m68k.org
2015-07-06 14:15 ` schwab@linux-m68k.org
2015-07-06 14:39 ` rguenth at gcc dot gnu.org [this message]
2015-07-06 14:43 ` rguenth at gcc dot gnu.org
2015-07-07  7:47 ` rguenth at gcc dot gnu.org
2015-07-07  8:01 ` rguenth at gcc dot gnu.org

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