CMPLOG llvm pass: use CreateIntCast to cast to the right integer type

[f0rki]

In the current dev branch I get errors while compiling a target with cmplog (afl-clang-lto++). My target uses bigints, which leads to trouble for the cmplog instrumentation. This PR fixes the issues (at least for me). Currently I get the following error:

Invalid bitcast
  %10 = bitcast i80 %9 to i128, !dbg !29860
in function _ZSt7signbite
LLVM ERROR: Broken function found, compilation aborted!

I think bitcast i80 to i128 doesn't work since bitcast only works with types of the exact same bit size. So we need to use zext instead to extend to i128 in the case above. I believe that CreateIntCast on the IRBuilder is the right function for this job (except we need a bitcast to an integer type first in case we are dealing with floating point values).

I think that previously 128 bit integer types were also implicitly truncated due to the use of uint64_t val = cint->getZExtValue(); to create a new constant integer. I haven't tested this, but this should be fixed now too.

[vanhauser-thc]

are you using afl-clang-lto?
because I implemented a fix for this like 4 hours ago :)

[f0rki]

lol. apparently afl++ dev speed is too fast for me. yes I am using clang LTO. yes it seems fixed in current dev.

But I am wondering whether I would loose instrumentation of some compare instructions with the current workaround in dev?

I think that previously 128 bit integer types were also implicitly truncated due to the use of uint64_t val = cint->getZExtValue(); to create a new constant integer.

Does this part still apply?

[vanhauser-thc]

I like your solution better than mine, in LTO I just skip this crashing bitcast. can you rework your PR to fit to the changed dev state?

[f0rki]

sure. I'll rebase and revert your workaround (edit: but probably tomorrow morning). Do you have another project where this issue comes up that I can use for testing?

[vanhauser-thc]

I think that previously 128 bit integer types were also implicitly truncated due to the use of uint64_t val = cint->getZExtValue(); to create a new constant integer.

Does this part still apply?

yes:
https://llvm.org/doxygen/classllvm_1_1ConstantInt.html#ac09a21c371a9c535cbc13e8f82503aec

[f0rki]

@vanhauser-thc done. rebased and reverted workaround.

[vanhauser-thc]

thank you!