https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87692
Bug ID: 87692
Summary: Reuse guard variable for multiple initializations
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: antoshkka at gmail dot com
Target Milestone: ---
Consider the following example:
int produce1();
int produce2(int ) noexcept;
auto test() {
static int val1 = produce1();
static int val2 = produce2(val1); // noexcept
return val2 + val2;
}
For the above example two guard variables are generated: for `val1` and `val2`.
However the `val2` initialization always succeeds and may not happen before
`val1` initialization.
So instead of having two variables, `val2` could reuse the guard variable for
`val1`.
Using one variable has advantages: less code is generated and no need in
multiple guard variables checks.
Such optimization will reduce the code size and improve overall performance.
