30434bab1a
This patch relands https://github.com/llvm/llvm-project/pull/182532. The original version causes test failures related undef bits since it incorrectly assumes `std::uniform_int_distribution` yields the same results across different stdlib vendors. This patch simply uses low bits to avoid the issue. I am not sure whether it still generates uniformly distributed random numbers. But abseil also uses this trick:e72b94a2f2/absl/random/uniform_int_distribution.h (L203-L206)I have confirmed all tests passed with libstdc++ and libc++. Original PR description: Bytes are adjusted to respect the incoming byte type proposed in https://discourse.llvm.org/t/rfc-add-a-new-byte-type-to-llvm-ir/89522. Note that the current implementation of constant folding doesn't handle bitcasts with weird types like `<8 x i3> to <3 x i8>`:49de34459c/llvm/lib/Analysis/ConstantFolding.cpp (L223-L232)So I take the result from Alive2 as reference: https://alive2.llvm.org/ce/z/ZGA_xP
92 lines
2.9 KiB
ReStructuredText
92 lines
2.9 KiB
ReStructuredText
llubi - LLVM UB-aware Interpreter
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=================================
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.. program:: llubi
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SYNOPSIS
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--------
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:program:`llubi` [*options*] [*filename*] [*program args*]
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DESCRIPTION
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-----------
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:program:`llubi` directly executes programs in LLVM bitcode format and tracks values in LLVM IR semantics.
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Unlike :program:`lli`, :program:`llubi` is designed to be aware of undefined behaviors during execution.
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It detects immediate undefined behaviors such as integer division by zero, and respects poison generating flags
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like `nsw` and `nuw`. As it captures most of the guardable undefined behaviors, it is highly suitable for
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constructing an interesting-ness test for miscompilation bugs.
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If `filename` is not specified, then :program:`llubi` reads the LLVM bitcode for the
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program from standard input.
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The optional *args* specified on the command line are passed to the program as
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arguments.
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GENERAL OPTIONS
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---------------
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.. option:: -fake-argv0=executable
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Override the ``argv[0]`` value passed into the executing program.
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.. option:: -entry-function=function
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Specify the name of the function to execute as the program's entry point.
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By default, :program:`llubi` uses the function named ``main``.
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.. option:: -help
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Print a summary of command line options.
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.. option:: -verbose
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Print results for each instruction executed.
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.. option:: -version
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Print out the version of :program:`llubi` and exit without doing anything else.
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INTERPRETER OPTIONS
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-------------------
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.. option:: -max-mem=N
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Limit the amount of memory (in bytes) that can be allocated by the program, including
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stack, heap, and global variables. If the limit is exceeded, execution will be terminated.
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By default, there is no limit (N = 0).
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.. option:: -max-stack-depth=N
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Limit the maximum stack depth to N. If the limit is exceeded, execution will be terminated.
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The default limit is 256. Set N to 0 to disable the limit.
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.. option:: -max-steps=N
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Limit the number of instructions executed to N. If the limit is reached, execution will
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be terminated. By default, there is no limit (N = 0).
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.. option:: -vscale=N
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Set the value of `llvm.vscale` to N. The default value is 4.
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.. option:: -seed=N
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Set the seed for random number generator to N. By default, the seed is 0.
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.. option:: -undef-behavior=mode
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Set the behavior for undefined values (e.g., load from uninitialized memory or freeze a poison value).
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The options for `mode` are:
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* `nondet`: Each load from the same uninitialized byte yields a freshly random value. This is the default behavior.
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* `zero`: Uninitialized values are treated as zero.
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EXIT STATUS
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-----------
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If :program:`llubi` fails to load the program, or an error occurs during execution (e.g, an immediate undefined
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behavior is triggered), it will exit with an exit code of 1.
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If the return type of entry function is not an integer type, it will return 0.
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Otherwise, it will return the exit code of the program.
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