const strings not consolidated in -O0

[llvmbot]

Bugzilla Link	12199
Version	3.0
OS	MacOS X
Reporter	LLVM Bugzilla Contributor

Extended Description

For the program below. clang 3.1 returns "different" unless you optimize it with -O2 or higher. In gcc 4.2 and VC, the code always return "same" no matter in -O0 or -O2.

Some code was written with this assumption, they know all the keys are from const strings so they do pointer compare instead string compare. There're might be more code relies on this behavior.

#include <stdio.h>
#define LAYER_KEY L"Layer"
struct TEST {
  const wchar_t* key;
}gTESTINFO = {
    LAYER_KEY
};

int main() {
    const wchar_t* key = LAYER_KEY;

    if (gTESTINFO.key == key)
        printf("same\n");
    else
        printf("different\n"); 
    return 0;
}

[llvmbot]

Reproduced with trunk (20130114) on MacOS X. Oddly does not occur on x86_64-linux.

[llvmbot]

http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-March/020070.html