[clang] [llvm] [HLSL][DXIL][SPRIV] Added WaveActiveProduct intrinsic #164385 (PR #165109)

[Nathan Gauër via llvm-commits]

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Keenuts wrote:

I think what Steven suggested was to have the scope + operation being an immediate operand to the builtin. Meaning thew CGHLSLBuiltin code would have to emit something  like
`llvm.spv.wave.product(i32 3, i32 0, i32 %iexpr)` so the Scope & Operation operands are something we can do in the FE, and it reduces the amount of intrinsics needed (as here, if we implement all SPIR-V intrinsics combinaisons, we'd have to add 8 (operations) x 7 (scope) intrinsincs to cover all combinaisons.

https://github.com/llvm/llvm-project/pull/165109