[aievec] to-llvm flow for aievec.ext op with I128.I512 extract intrinsic #1490
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| // CHECK-SAME: (vector<16xi32>) -> vector<4xi32> | ||
| // CHECK-NEXT: %[[RES0:.*]] = llvm.bitcast %[[EXT0]] : vector<4xi32> to vector<4xf32> | ||
| // CHECK-NEXT: %[[UNDEF1:.*]] = "xllvm.intr.aie2.v16int32"() : () -> vector<16xi32> | ||
| // CHECK-NEXT: %[[CST48:.*]] = llvm.mlir.constant(48 : i32) : i32 |
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Is this correct? If I understand correctly, the process to extract a subvector from a given position is to shift the whole vector by the number of bits up to the position, and then extracting the lowest part. For 16-bit element vectors and an extraction from position 3, that's 3 x 16 = 48 bit, but for 32-bit element vectors, shouldn't it be 3 x 32 = 96 bit? Am I misunderstanding something?
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The shift amount for the shift op/intrinsic is in the number of bytes. The I128.I512 extract intrinsic is special. It always extracts the lowest 128-bit vector from the source 512-bit vector. For index=0 vector extraction, we actually don't need any vector shift beforehand, so I have updated the conversion pattern for this scenario. As for index=3 vector extraction, the shift amount is 48 bytes = 384 bits = 3*128 bits. After the right shift of 48 bytes, the I128.I512 intrinsic extracts the lowest 128-bit vector, which is correct. I have updated the aievec.ext/shift op descriptions, to explicitly clarify the shift amount in bytes and the extraction index to be either 0--1 or 0--3. Let me know if there is anything else I can do :).
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Aaaah! Got it, I was trying to make the maths work in my head and failing, thanks for the clarification 🙂
This PR add the support for aievec.ext op going through the to-llvm flow with the
extract.I128.I512intrinsic op.Changes:
extract.I128.I512intrinsic ops in XLLVM dialect.extract.I128.I512intrinsic.