Assertion failed: (Exp != 0 && "Incorrect exponent 0 not handled"), function getPow, on std::pow(n, -0.0)

[zamazan4ik]

Bugzilla Link	43233
Resolution	FIXED
Resolved on	Sep 09, 2019 03:54
Version	trunk
OS	Linux
Blocks	#41819
CC	@DougGregor,@DimitryAndric,@zmodem,@RKSimon,@zygoloid,@rotateright

Extended Description

For the code:

#include

double t1(double n) {
return std::pow(n, -0.0);
}

clang (trunk, 8.0) crashes with the follworing message: https://pastebin.com/w7nVhwtu

clang 7.0 and below works fine.

Godbolt playground: https://godbolt.org/z/aRbTH0

[zamazan4ik]

assigned to @rotateright

[DimitryAndric]

FWIW, this is triggered in particular by -ffast-math:

$ cat pr43233-min.cpp
// clang -cc1 -triple x86_64-- -S -ffast-math -O1 pr43233-min.cpp

extern "C" double pow(double, double);

double f(double d)
{
return pow(d, -0.0);
}

$ clang -cc1 -triple x86_64-- -S -ffast-math -O1 pr43233-min.cpp
Assertion failed: (Exp != 0 && "Incorrect exponent 0 not handled"), function getPow, file llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp, line 1170.
Abort trap

It looks like this regressed with https://reviews.llvm.org/rL339578 ("[SLC] Expand simplification of pow() for vector types") by evandro.

[rotateright]

It looks like this regressed with https://reviews.llvm.org/rL339578 ("[SLC]
Expand simplification of pow() for vector types") by evandro.

Yes - this was an unintentional diff:
ExpoC->getValueAPF().isZero() handles either -0.0/+0.0, but m_SpecificFP(0.0) does not.

I can fix this.

[llvmbot]

Thank you.

[rotateright]

Trunk fix committed:
https://reviews.llvm.org/rL371221

And I didn't know it, but there was an identical patch in progress in here:
https://reviews.llvm.org/D67248

We probably want to get this fixed in the branches too, so not marking as resolved yet.

[zmodem]

Merged to release_90 in r371381.

[rotateright]

Merged to release_90 in r371381.

Thanks, Hans!