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From: Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>
Date: Tue, 06 Mar 2018 12:01:00 -0000
Message-ID: <CAAgBjMkcuch04W94DB06Vv7oYZQPLk2VRN5ALd_0Vt=CmzZ=-w@mail.gmail.com>
Subject: eliminate dead stores across functions
To: gcc@gcc.gnu.org
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Hi,
For the following test-case,

int a;

__attribute__((noinline))
static void foo()
{
  a = 3;
}

int main()
{
  a = 4;
  foo ();
  return a;
}

I assume it's safe to remove "a = 4"  since 'a' would be overwritten
by call to foo ?
IIUC, ipa-reference pass does mod/ref analysis to compute side-effects
of function call,
so could we perhaps use ipa_reference_get_not_written_global() in dse
pass to check if a global variable will be killed on call to a
function ? If not, I suppose we could write a similar ipa pass that
computes the set of killed global variables per function but I am not
sure if that's the correct approach.

Thanks,
Prathamesh