[PATCH] D117210: [CodeGen] Support folds of not(cmp(cc, ...)) -> cmp(!cc, ...) for scalable vectors

[David Sherwood via Phabricator via llvm-commits]

david-arm added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:3175
+             isa<ConstantSDNode>(N->getOperand(0))) {
+    CVal = cast<ConstantSDNode>(N->getOperand(0))->getAPIntValue();
   } else {
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frasercrmck wrote:
> I think we have to support the truncating case as with `BUILD_VECTOR` above, don't we?
Hmm, I looked at the definition of SPLAT_VECTOR and you're right - the operand is allowed to be wider than the vector element type of the result. I hadn't realised that :(. The only problem is that I have absolutely no idea how to write a test case for this using IR! I'm not sure if there is a way to create a splat (using SPLAT_VECTOR) in IR that is truncating. Unless you know of any RISCV examples where this would happen?


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  https://reviews.llvm.org/D117210/new/

https://reviews.llvm.org/D117210