[llvm-branch-commits] [llvm] [SLP] Drop the context of a vector fmul whose user is not vectorized (PR #228902)

[Dmitry Sidorov via llvm-branch-commits]

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@@ -17575,9 +17575,22 @@ BoUpSLP::getEntryCost(const TreeEntry *E, ArrayRef<Value *> VectorizedVals,
       unsigned OpIdx = isa<UnaryOperator>(VL0) ? 0 : 1;
       TTI::OperandValueInfo Op1Info = getOperandInfo(E->getOperand(0));
       TTI::OperandValueInfo Op2Info = getOperandInfo(E->getOperand(OpIdx));
+      // A target may price an fmul by the fadd or fsub user of its context.
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MrSidims wrote:

I agree that target-specific fusion decisions belong in TTI, but the transform-specific information has to come from SLP. A TTI-only type check can conservatively reject the discount, but cannot distinguish these cases.

https://github.com/llvm/llvm-project/pull/228902