[llvm] Calculate KnownBits from Metadata correctly for vector loads (PR #128908)

[via llvm-commits]

LU-JOHN wrote:

> I keep running out of disk space on my test machine (sigh) when I do debuginfo builds, but with assertions I got as far as `` src/llvm-project/llvm/include/llvm/ADT/APInt.h:1369: void llvm::APInt::setBits(unsigned int, unsigned int): Assertion `loBit <= BitWidth && "loBit out of range"' failed. `` Sadly no stack trace on that though.

I suspect that in the code:

>       KnownBits KnownScalarMemory(ScalarMemorySize);
>       if (const MDNode *MD = LD->getRanges())
>         computeKnownBitsFromRangeMetadata(*MD, KnownScalarMemory);

the range metadata bitwidth does not == ScalarMemorySize when you see a crash.   I thought that this should not
be possible, and I believe that the range metadata and load are incompatible.  Can you try changing the code to:

>       if (const MDNode *MD = LD->getRanges()) {
>         ConstantInt *Lower = mdconst::extract<ConstantInt>(MD->getOperand(0));
>         if (Lower->getBitWidth() != ScalarMemorySize) {
>           LD->dump();
>           MD->dump();
>           assert(0);
>         }
>         computeKnownBitsFromRangeMetadata(*MD, KnownScalarMemory);
>       }
> 


https://github.com/llvm/llvm-project/pull/128908