[cfe-dev] static const function locals

Peter Cooper peter_cooper at apple.com
Mon Jun 18 10:47:48 PDT 2012

Hi all

I'm trying to write an optimization to create constant initializers for static const locals where they are structures, i.e., on this test

struct S {
	int i;
	S(int v) : i(v) { } 

int foo(int i) {
	static const S arr[4] = {0,1,2,3};
	return arr[i].i;

i'm going to change the IR so that instead of a series of stores guarded by __cxa_guard functions, we just have

@_ZZ3fooiE3arr = constant global [4 x %struct.S] [%struct.S { i32 0}, %struct.S { i32 1}, %struct.S { i32 2}, %struct.S { i32 3}]

However, the global has been given a zero initializer which makes doing this change difficult without more analysis than I think is necessary.

So, finally, my question is, can we put an undef initializer on this variable instead of a zero initializer?  I don't know the C++ spec so i'm not sure if i'm missing something.


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