[LLVMdev] [icFuzz] Help needed with analyzing randomly generated tests that fail on clang 3.4 trunk

[Haghighat, Mohammad R]

The tests by design are syntactically correct, semantically correct, and have deterministic output.

-moh

From: Nick Lewycky [mailto:nlewycky at google.com]
Sent: Monday, June 24, 2013 4:14 PM
To: Haghighat, Mohammad R
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] [icFuzz] Help needed with analyzing randomly generated tests that fail on clang 3.4 trunk

On 24 June 2013 16:10, Haghighat, Mohammad R <mohammad.r.haghighat at intel.com<mailto:mohammad.r.haghighat at intel.com>> wrote:
Hi,

I just submitted a bug report with a package containing 107 small test cases that fail on the latest LLVM/clang 3.4 main trunk (184563). Included are test sources, compilation commands, test input files, and results at -O0 and -O2 when applicable.

http://llvm.org/bugs/show_bug.cgi?id=16431


These tests have been automatically generated by an internal tool at Intel, the Intel Compiler fuzzer, icFuzz. The tests are typically very small. For example, for the following simple loop (test t5702) on MacOS X, clang at -O2 generates a binary that crashes:


// Test Loop Interchange
for (j = 2; j < 76; j++) {
    for (jm = 1; jm < 30; jm++) {
        h[j-1][jm-1] = j + 83;
    }
}

The tests are put in to two categories
- tests that have different runtime outputs when compiled at -O0 and -O2 (this category also includes runtime crashes)

Are these tests generated in a manner such that they have a very low probability of using undefined behaviour?

Nick

- tests that cause infinite loops in the Clang optimizer

Many of these failing tests could be due to the same bug, thus a much smaller number of root problems are expected.

Any help with triaging these bugs would be highly appreciated.

Thanks,
-moh



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