[LLVMbugs] [Bug 12199] New: const strings not consolidated in -O0

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12199

             Bug #: 12199
           Summary: const strings not consolidated in -O0
           Product: clang
           Version: 3.0
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: yingshen.yu at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


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;
}

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