[LLVMbugs] [Bug 14506] New: Loop condition not checked with -O1 and assert()

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http://llvm.org/bugs/show_bug.cgi?id=14506

             Bug #: 14506
           Summary: Loop condition not checked with -O1 and assert()
           Product: clang
           Version: 3.1
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: llvm at yorhel.nl
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Hello,

I ran into an odd issue. The following example illustrates the problem:


#include <assert.h>

int main(int argc, char **argv) {
    int l, i;

    for(i=0; i<1; i++)
        ;

    for(l=0,i=0; i<1; i++) {
        l++;
        assert(l == i+1);
    }
    return 0;
}


When compiled with 'clang -O1', the second loop does not terminate as it
should. The program terminates correctly when compiled with -DNDEBUG or with
-O0.

$ clang --version
clang version 3.1 (branches/release_31)
Target: x86_64-unknown-linux-gnu
Thread model: posix

This is on Arch Linux with the clang-3.1-6 package.

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