[llvm] [AMDGPU] Price the packed form of a vector of i1 (PR #217327)

[Frederik Harwath via llvm-commits]

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@@ -980,13 +980,59 @@ InstructionCost GCNTTIImpl::getCFInstrCost(unsigned Opcode,
   return BaseT::getCFInstrCost(Opcode, CostKind, I);
 }
 
+// A vector of i1 has no packed form on this target: every element lives in its
+// own mask. Measured instruction counts per element to pack the masks into an
+// integer, and to unpack them again.
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frederik-h wrote:

Add information from the PR description about the gfx versions and the observed value range to the comment?

https://github.com/llvm/llvm-project/pull/217327