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LLVM backend for 6502
c16105b078
tricky case of single-element insertion into the zero lane of a zero vector. We can't just use the same pattern here as we do in every other vector type because the general insertion logic can handle insertion into the non-zero lane of the vector. However, in SSE4.1 with v4f32 vectors we have INSERTPS that is a much better choice than the generic one for such lowerings. But INSERTPS can do lots of other lowerings as well so factoring its logic into the general insertion logic doesn't work very well. We also can't just extract the core common part of the general insertion logic that is faster (forming VZEXT_MOVL synthetic nodes that lower to MOVSS when they can) because VZEXT_MOVL is often *faster* than a blend while INSERTPS is slower! So instead we do a restrictive condition on attempting to use the generic insertion logic to narrow it to those cases where VZEXT_MOVL won't need a shuffle afterward and thus will do better than INSERTPS. Then we try blending. Then we go back to INSERTPS. This still doesn't generate perfect code for some silly reasons that can be fixed by tweaking the td files for lowering VZEXT_MOVL to use XORPS+BLENDPS when available rather than XORPS+MOVSS when the input ends up in a register rather than a load from memory -- BLENDPSrr has twice the reciprocal throughput of MOVSSrr. Don't you love this ISA? git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218177 91177308-0d34-0410-b5e6-96231b3b80d8 |
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| README.txt | ||
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