Missing deopt for MIN_VALUE / -1 case causes crash from unhandled SIGFPE

Jackson Davis jackson at jcdav.is
Fri Dec 1 08:04:47 UTC 2017

One afternoon over Thanksgiving break I hacked together a very basic fuzzer
for JVM JITs (https://github.com/jcdavis/kabur/) which much to my surprise
actually managed to find an issue in Graal :)
This minimal test case reliably crashes the JVM from an unhandled SIGFPE:

public class Crasher {
  public static int crash(int n, int d) {
    return n/(d|1);
  public static void main(String[] args) {
    for(int i = 0; i < 100000; i++) {
      crash(i, i+1);
    crash(Integer.MIN_VALUE, -1);
Ran with -XX:+UseJVMCICompiler -XX:-TieredCompilation
-XX:-BackgroundCompilation (Tested with local jdk9 and graal master)

The source of this issue appears to be that IntegerDivRemNode.canDeoptimize
only checks whether or not the denominator can be 0, not whether it can
also be -1. Since d|1 is never 0, it doesn't generate the appropriate deopt
info, so when MIN_VALUE/-1 causes a SIGFPE, the signal handler doesn't know
what to do and dies. Adding the -1 check seems to make this to work as
intended (AFAICT). I have a PR for a basic fix here:

Unfortunately this check breaks CountedLoopTest in a non-obvious way, which
is where I am out of my depth. It seems the test's CheckGraphPhase
introduces a SignedDivNode, however since this runs after
FrameStateAssignmentPhase, there is no frame data, so an assert fails in
the lowering. This seems to be fundamentally broken regardless of my
change, but only started failing here since the denominator has as stamp of


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