clang promoting local to global

I have a const array allocated inside a function and the IR is showing this has a global function (ie. there is no allocation for the space inside the function).

For example:

const int32 local_array[256] = {constValue, constValue, … }

Is there any particular reason this may be occuring?

Thanks.

It's an optimization; IIRC, you can turn it off with -fno-merge-all-constants.

-Eli

Eli, thanks for responding, unfortunately, this did not resolve my issue. It’s a locally allocated array in the C code, but I’m not seeing any alloca in the IR just geps from the variable, which is never setup.

That's strange; I just checked, and -fno-merge-all-constants
definitely does have an effect for a simple testcase like the
following (just using clang -emit-llvm at -O0):

void f() { const int x[5] = {1,2,3,4}; }

What does your testcase look like?

-Eli

#define r10(p,q,r,s) 0x##s##r##q##p
#undef r
#define r r10
const word it_tab[4][256] = { r(const, const, const, const), r(…), r(…) … };

All of this is done inside the function I want the alloc in. The variable is not declared/defined/used anywhere else.

So there are some #define (defined outside the function scope) that use it_tab that are used inside the function, is this why it is promoting it to a global?

So there are some #define (defined outside the function scope) that use
it_tab that are used inside the function, is this why it is promoting it to
a global?

Macros shouldn't matter. Please give a complete testcase and steps to
reproduce. And please don't top-post.

-Eli

#define other_def(x, tab, vf, rf, c) (x ^ tab[0][x ^ c0 ^ vf ^ rf ^ c)
#define my_def(y,x,k,c) defs(y,c) = (k}[c] ^ other_def(x, it_tab, inv_var, rf1, c)
void my_func() {
#define r10(p,q,r,s) 0x##s##r##q##p
#undef r
#define r r10
const word it_tab[4][256] = { r(const, const, const, const), r(…), r(…) … };
}

You prefer bottom posting? Ok.

That’s not a complete testcase; it isn’t valid C. Also, please give steps to reproduce the problem (what commands you ran) and tell us what output you got.